# Dampers (Shocks) .... little bit more about them



## pyce (Nov 7, 2001)

If you are on the market for dampers, probably it is not going to be a bad idea to stop by and check this thread. The idea behind is to first try to find a set of the most popular dampers for the MkIV (A4) chassis. Then dyno them on a so called “shock dyno”. See how do they all compare and then install them on the car and use an accelerometer as to get graphs from the various dampers in action in real life conditions and then see how those results compare to what the dyno charts are telling us…… So, perhaps we can use the data and finally have some slightly more scientific way of comparing dampers.
The “shock dyno” is a Roehrig 10VS damper dynamometer. For those who want to know more, this is their web site: http://www.roehrigengineering.com As a quick quote from there, for those who do not want to waste time in browsing: The 10VS is commonly used in a research and development facility, portable damper development support trailer, or a race team’s shop. The 10VS is fully computer controlled using the SHOCK™ Test Control and Damper Analysis software. The standard 10VS features six English or Metric strokes up to 4 inches (100mm). It has a force capacity to +/- 3,500 lbs. and velocities up to +/- 38 ips (0.9 m/sec). Higher velocities are available as an option. The 10VS is the system of choice by many of the world’s leading automotive companies and OEM damper manufacturers for their vehicle ride and handling activities…..
Here is how it looks like. The computer is not shown, but it is a simple PC with appropriate software and that is it:








The “accelerometer” is a Low-G type from Vernier. For those who want to know more, their site is: http://www.vernier.com It is a one-axis accelerometer, as we are interested (at the moment) at only vertical accelerations. It is incredibly sensitive for our case, with possibility to record up to 500 samples per second! It will measure accelerations in the range of -5G (-49 m/s2) to +5G (+49 m/s2), which really exceeds what we need. It comes with a software and USB cable, so it is quiet user friendly and extremely easy to use by anyone with no requirement to read much from the manual. It is very small, basically fits nicely in your hand, and very light, so it could be mounted almost anywhere in the car. Here is how it looks like:








The first round dampers to go on the dyno are:
1. Stock OE (Boge-Sachs – p/n xxxxxxxxx ) with about 10.000 miles on it.
2. Koni Sport (Yellow – p/n xxxxxxxx) with about 15.000 miles on it.(tested at full soft and full stiff!)
3. Bilstein TC Sport (p/n xxxxxxxxx) with about 1.000 miles on it.
Later on, probably next week, will dyno the remaining: Bilstein HD, Bilstein Sport, Bilstein TC normal, Boge TurboGas and two other stock OE dampers, one is from 2002 car with 90.000 miles and another is pretty freash, but from 2003 model, so it is Monroe. Then there is a plan to try to rebuild one or two of these, and see how do they behave before/after, in an attempt to understand how all this work and how can (if possible) we have the cake and try to taste it too







I was thinking to put all this stuff together first and then post it, but then realized that the data is quiet a lot and probably would be much better if we split it somehow and feed this thread as we go…..
So, here we go with the first round of graphs, the Force vs. Displacement. Basically what was done is mount the damper, set the height so the damper will work around the physical range it works when on the car. Then the machine starts compressing-decompressing the damper (converting rotation to linear motion, imagine crank, rod and piston) at certain not very high speed. There is an infrared sensor that is pointed towards the middle of the body of the damper, so on the screen we see the temperature of the damper itself, at specific point that could be arranged. This is done so all dampers do get to the same exact temperature and then the separate cycles start, so to ensure some sort of consistency. It is very interesting to see how incredibly fast dampers heat and how much that heat affects the results, but on this one we will stop later. Then the dyno performs 2 in/sec movements several times, records the data as a graph, then moves to 4 in/sec, then to 6 and the last one is 30 in/sec. that is the fastest it can go. Here we have the graphs for the three dampers:
































Then there are several more graphs, that represent Force vs. Velocity and several other ways of comparing them, but that would be too much of pictures for the moment. I will eventually upload them as links, just for the more interested to check all the possible plots that dyno provides. This is just the first round. Later on we will separate each speed and make plots where all three dampers could be seen on the same page, so this way to easily compare the curves. We will see later how there is quiet a substantial difference from what the dyno tells us and what the real life road tells us for each damper. That is where the accelerometer comes to play and shows clearly the difference in ride comfort for each unit. I will edit this topic later on and add the part numbers for the above dampers.
More later.


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## MikekiM (Aug 21, 2001)

Nice equipment to get your hands on.








Great graphs (any chance you can shrink them a bit?)
Just a couple observations from those graphcs.
TC's appear to have good rebound control, making them suitable for a conversative lowering spring. They appear to ride a bit more firm than stock, all in all a nice upgrade.
I"m interested to learn the differnce in the highest speed piston movement between KONI soft and stiff. These should be identical, as the adjusting mechanism only touched the foot valve, not the piston valve, which controls compression.

Definitely looking forward to updates!


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## r03 (Nov 18, 2003)

great work. this thread literally made me hot. http://****************.com/smile/emthup.gif
get some of the blingier coilovers on there!


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## Ceilidh (Jan 7, 2004)

*Re: Dampers (Shocks) .... little bit more about them (pyce)*

Hi Peter,
Welcome back! Nice to see the graphs online...
Quick question:
What are the "speeds" indicated on the graphs? Are they the actual stroke speeds of the shocks, or do they indicate the tangential velocity of the test rig's "crankshaft"?
The reason I ask is that if the "speed" is the crankshaft speed, the shock will only have a comparable stroke speed at "0.0" displacement, and it'll actually be slower as it approaches the ends of its travel (in this case, the stroke velocity will be a sinusoid). That would explain the rounded shape of many of the curves, wherein the greatest forces occur at zero displacement (where velocity on the test rig is highest).
Here's another way to phrase the question: when you watched the measurements, did you notice whether the test rig ran at a constant rotational speed (rpm of the crankshaft) in each run? And did each run produce a single one of the coloured lines in the output graph? If so, each line is the crankpin speed, and the stroke speed is changing as described above. (If not, then I've a lot of head scratching to do in interpreting these graphs!)
Thanks for the great work, Peter!
- C (W)
P.S. -- at some point, could you please test a rear Koni at the 1/4 turn (90 degree) setting? I'd be curious to see what makes that setting a good comfort point. Thanks again!


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## ewongkaizen (Apr 19, 2002)

*Re: Dampers (Ceilidh)*

Here's a "dumb" thought...
Slapt he accelerometers on the shock on the dyno.
That way its easier to compare the "real world" versus the dyno.
My "guess" is tahat you need TWO accelerometers per shock
- one on the fixed portion
- one on the moving portion
For the dyno, the fixed on will stay fixed - ont eh moving one it also allos you to filter out hte road effects (aka the car physically moving up/down)


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## pyce (Nov 7, 2001)

*Re: Dampers (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_ ..... What are the "speeds" indicated on the graphs? Are they the actual stroke speeds of the shocks, or do they indicate the tangential velocity of the test rig's "crankshaft"?
The reason I ask is that if the "speed" is the crankshaft speed, the shock will only have a comparable stroke speed at "0.0" displacement, and it'll actually be slower as it approaches the ends of its travel (in this case, the stroke velocity will be a sinusoid). That would explain the rounded shape of many of the curves, wherein the greatest forces occur at zero displacement (where velocity on the test rig is highest)..... 

Yes, the speeds (from 2 in/sec to 30 in/sec) are the tangential speed of the crankshaft, so as you said, the full speed is around the "0,0" displacement. So, in a way, the dyno results do not quiet represent the real life situation as the speed they are tested kind of gradually ramps up and allow more of an ideal scenario for the damper to give its best. In real life, the potholes behave differently, and here is why the dyno results could be quiet misleading. I guess an expert can draw very stable conclusions even from looking those charts, but I am not such and therefore we went for the use of the accelerometer, as to prove the differences between the dyno results and real life. BTW, the idea of that accelerometer came from you and we all owe you one for that! It will simply transform the way we look at suspension from now on. We will be able to finally compare different setups in a more scientific way instead of the usual “this is more comfy than that” type we used till now. 


_Quote, originally posted by *Ceilidh* »_ P.S. -- at some point, could you please test a rear Koni at the 1/4 turn (90 degree) setting? I'd be curious to see what makes that setting a good comfort point. Thanks again!

That is in the plans, but it may happen only at the very end. I am actually very interested in taking that damper apart and see what is going on inside and watch the dyno guy rebuilding it, so perhaps we can grasp little bit more from the whole concept. If it is not terribly complicated, we can build a quick virtual model and come out with few animations, as to visualize how this whole thing works inside. 

_Quote, originally posted by *MikekiM* »_ ….Just a couple observations from those graphcs. TC's appear to have good rebound control, making them suitable for a conversative lowering spring. They appear to ride a bit more firm than stock, all in all a nice upgrade. 

We will find out later on that the TC look good “on paper” (from the dyno, as you observed) but it is quiet far from being the advertised 10 or 20% “stiffer” than stock. I will try to get there today…

_Quote, originally posted by *MikekiM* »_ …. I"m interested to learn the differnce in the highest speed piston movement between KONI soft and stiff. These should be identical, as the adjusting mechanism only touched the foot valve, not the piston valve, which controls compression.

In fact, the compression is “almost” indentical at all speeds we tested. I am saying “almost” because there is a very slight difference between the lines, but that could very much be the result of slightly different “zeroing” the damper between the two runs. They are so close that it is absolutely safe to say they are identical. So, the Koni advertising that Koni Sport acts only on rebound and the compression is always the same is correct.

_Quote, originally posted by *ewongkaizen* »_....Slap the accelerometers on the shock on the dyno. That way its easier to compare the "real world" versus the dyno.....

I do not fully understand how would that help? The damper on the dyno is moved up and down by the crank, so the accelerations (vertical, on the damper) are related to the circular motion of the crank. That thing is so smooth, that is we were to put the accelerometer on there, I guess we would get a very nice sinusoidal line….. I just do not understand how to use later this smooth line in comparison to what the real street accelerations are? Perhaps I did not fully understand your thought, please explain more.
Sorry everyone for the big pictures (they were bigger), but they looked pretty small on my screen. I do understand people with laptops suffer with big pictures, but at the same time people with very high resolution monitors may have trouble reading well the pictures…. Hope the current resolution works well for both worlds.


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## pyce (Nov 7, 2001)

*Dampers at 18 in/sec*

Here is a comparison of all three dampers at 18 in/sec. Unfortunately the software choose very similar colors for the Koni on full soft and full stiff, but the lines are quiet far from each other in the rebound stroke – it is easy to guess which is which. On the top side (the compression stroke) we can see both lines almost on top of each other, which is part of the proof that compression does not change when adjusting a Koni Yellow… at least does not change in a way that matters much for our application…


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## phatvw (Aug 29, 2001)

*Re: Dampers (pyce)*

I'm very curious about the Bilstein results.
Also, are you going to be testing both with and without the rubber shock buffers? The Bilsteins have the built-in buffers so it may not be a fair comparison with the other dampers. I know the buffers affect compression a great deal, but I wonder about rebound as well? The energy stored up in the compressed buffer must exert some force on rebound...
Great job btw!! Those graphs are excellent!
http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif


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## Ceilidh (Jan 7, 2004)

*Re: Dampers at 18 in/sec (pyce)*


_Quote, originally posted by *pyce* »_Here is a comparison of all three dampers at 18 in/sec...


Very interesting asymmetry, Peter, particularly on the compression side. Can you confirm that the plot trace goes in the clockwise direction (i.e., that the upper left quadrant shows the shock contracting from full droop, and that a negative (-) displacement on the horizontal axis corresponds to extension from baseline)?
If you can confirm the above, then we at last have possible empirical proof of the "slow-action" twin-tube characteristic that's supposed to be one reason why the Koni's are so much less punishing on sharp impacts. (That is, the asymmetry shows that when a wheel first hits a bump, the shock forces build up only gradually.) If the Bilstein HD's turn out to have a much steeper ramp in the upper left quadrant (i.e., if it looks like the Koni upper right quadrant), then that would complete the proof.
Very interesting, Peter -- keep 'em coming!
- C


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## pyce (Nov 7, 2001)

*ole!*


_Quote, originally posted by *phatvw* »_....Also, are you going to be testing both with and without the rubber shock buffers? The Bilsteins have the built-in buffers so it may not be a fair comparison with the other dampers. I know the buffers affect compression a great deal, but I wonder about rebound as well? The energy stored up in the compressed buffer must exert some force on rebound...

Phat, the dyno is designed in a way that only rear dampers could be tested. Well, actually I am sure some sort of adaptors could be manufactured and perhaps manage to grab even a front damper, but I am really not that interested in the fronts now. It cost 25$ each time the machine goes on and I rather invest in something else than dynoing fronts as well...... so this leaves us with the rears, where I am not sure internal buffers are involved. If you intend the bump stops we have in the rear, they do not come into play anyway, as the dyno has full stroke of 2" and it never goes all the way up or down. Our rear dampers have full stroke of 9", so it is up to us to decide where to position the damper. We actually took some measurements and found out that the damper works (when on the car) at around 5,5" to 6" from fully compressed, so that is where we fix the damper for the dyno. This way if (just in case) it is not so linear, then we have closer to our daily driving scenario.

_Quote, originally posted by *Ceilidh* »_ .....Can you confirm that the plot trace goes in the clockwise direction (i.e., that the upper left quadrant shows the shock contracting from full droop, and that a negative (-) displacement on the horizontal axis corresponds to extension from baseline)?

Yes, it goes clockwise. Basically at 9 o’clock of the graphs the dampers is fully extended (+1”), then at 12 o’clock it is half way compressed (highest speed here too) than at 3 o’clock is fully compressed (-1”). At 6 o’clock is again half way, but in rebound (again, highest speed here)…and the circle is closed.


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## pyce (Nov 7, 2001)

*Some graphs....*

So, here is basically what the Accelerometer can give us. Below are two graphs, collected on the same day, same car, same road, same speed (used cruise control to be accurate!). The only variation made between the two runs is the tire pressure. Car is a NB, so it has 16” tires, Energy M+S type. The green graph is going one way and the red is coming back. Both graphs are sized in the same way, so the scale is the same…… It shows basically two things, to begin with:
1. Tire pressure difference of 8 PSI makes huge difference in comfort (40 PSI vs 32 PSI).
2. Our roads are quiet crappy! Consider that accelerations of 0,3 are the comfort limit (numbers taken from some books on suspension), from 0,3 to 0,6 is the “yellow” zone, and beyond 0,6 is where the discomfort starts. So, you all can see what kind of discomfort is just to go up and down the street.


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## Ceilidh (Jan 7, 2004)

*Re: Some graphs.... (pyce)*


_Quote, originally posted by *pyce* »_So, here is basically what the Accelerometer can give us. Below are two graphs, collected on the same day, same car, same .........Our roads are quiet crappy! Consider that accelerations of 0,3 are the comfort limit (numbers taken from some books on suspension), from 0,3 to 0,6 is the “yellow” zone, and beyond 0,6 is where the discomfort starts. So, you all can see what kind of discomfort is just to go up and down the street.


Hi Peter,
I've just noticed that your biggest rebound spikes go beyond -9 m/s^2 -- considering that gravitational acceleration "g" is only -9.8 m/s^2, that means you're close to airborne! Definitely some really bad roads out there; no wonder ride comfort is an issue.








Thanks very much for pointing out the ride comfort degradation from high tire pressures!
- C


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## pyce (Nov 7, 2001)

*The TC vs. Koni....*

Now, here it gets more interesting….. we have the same car, same road, same day, speeds, etc, plus we have the same tire pressure at the rear (32 PSI), but this time on a Jetta that has the stock sport package rear springs and one the first graph is equipped with Koni Yellow on the rears, set at about ¼ turn from stiff (about 12% stiff). The second graphs is when the car is equipped with Bilstein TC Sport on the rear….
















Here is where basically the things get very interesting. As you all can see, the dyno showed how the TC Sport are (as also advertised) pretty close to stock, if we look at the compression. The rebound is quiet more than stock thought. But from the graphs is pretty clear that the TC is not any near the advertised 10 or 20% stiffer than stock, because even if it “ideally” is (reading the dyno it could be decided that it is 10-20% stiffer), it definitely it is not according the vertical accelerations in the car. Basically, what I am trying to say here is: They may have dynoed those two dampers (OE and TC) and from the graphs (specially looking at the compression, which they say is more important fro comfort!) it is easy to come out with the conclusion that the TC is 10-20% stiffer than OE, but apparently 10-20% difference on the dyno curve is not really 10-20% difference in real life. Or perhaps it all lies in somewhere else? I have to yet do the accelerometer on OE rear dampers on the Jetta (as it has 15” tires) and then we will see how these two compare to the OE, but for the moment it is pretty clear that a Koni set to 12% rebound in the rear is significantly more comfortable on the same car, same conditions than a TC Sport.
The question here is WHY? Is the rebound the cause of the discomfort (which rebound the TC has much stronger than the Koni at that particular 12%) Or is it something else? 
While doing the dynos, I was also talking to the dyno owner (his name is Phil, locals may know him as a big and famous motorbike nut) about these results and how the real life accelerations do not quiet match with what we can see from the dyno. Now, he had not seen the accelerometer’s graphs, neither he knew these dampers well as his world is bikes and not cars, but while looking at the dynos, he managed to describe to me exactly how these dampers would perform in real life and his description fully coincided with my butt feelings, so I would like to rephrase now what he said, what could possibly makes the TC such a harsh damper, even if the absolute values of the curves do show it as a nice mild upgrade. So, here is what he tried to explain to me:
Let’s take a look at the upper left part of the 18 in/sec graph, sort of zoom-in and analyze those three lines from the three dampers. Here it is again in detail:








If we look carefully at the TC line, is starts ramping up as fast and steep as the Koni line. At certain point thought, very close to the start of compression, it bends quiet fast towards the right and “flattens” pretty fast, as to join the OE line where the max speed is (extreme right on the picture). So, according the Phil, this is precisely the reason the TC do ride bad, because the valving inside is kind of very inconsistent. Basically, what he was trying to tell me is that the valve holds pretty well the initial pressure, but once it opens, it lets the fluid go too fast, so there is very quick drop in pressure, at which point the damper does no longer perform in a smooth way, which is apparently what it takes for good comfort…..
I have to go now, but we will dig more into this later.


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## alexb75 (Dec 29, 2002)

*Re: The TC vs. Koni.... (pyce)*

WOW








All I can say is THANKS ... GREAT JOB MAN... this is amazing, it will totally show why some shocks behave they way they do! Specially your real life accelerometer results are PRICELESS... as we all know Dynoing is only half of the story and probably best for marketing.
I do NOT believe any of the tuners out there dared to do similar tests (at least I am not aware of) and no one would be brave enough to publish findings... You may wanna send a resume to Car&Driver... they probably can use someone like you








Looking forward to the rest of the results. http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif


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## Ceilidh (Jan 7, 2004)

*Re: The TC vs. Koni.... (pyce)*


_Quote, originally posted by *pyce* »_.......The question here is WHY? Is the rebound the cause of the discomfort (which rebound the TC has much stronger than the Koni at that particular 12%) Or is it something else? 
........according the Phil, this is precisely the reason the TC do ride bad, because the valving inside is kind of very inconsistent. Basically, what he was trying to tell me is that the valve holds pretty well the initial pressure, but once it opens, it lets the fluid go too fast, so there is very quick drop in pressure, at which point the damper does no longer perform in a smooth way, which is apparently what it takes for good comfort….. 


Hello Everyone,
Peter and I have been emailing back and forth a bit about the shock absorber tests, and he's asked me to post one of the emails. I'm afraid I don't have time to edit it and fix it up for Vortex use, but with the context Peter's given in his last post, it should be understandable. The only thing to note are that (1) Peter's sent me pages of a shock absorber text he found in London, which did much to illuminate what appears to be going on, and (2) before the appearance of his textbook, we had two possible explanations for the TC's poor performance, one of which (inertial overshoot) no longer seems to be an issue.
Anyway, here's the message, verbatim:
Hi Peter,

I just wanted to let you know that the articles were excellent! Very informative, and they've got me thinking....

1) Remember when I said there were two ways of interpreting Phil's comments, that either he was referring to the steady state characteristics of the shock valving, or else to some time delays and overshoots arising from inertial forces in the valves? Well, the articles sort of imply that it's the former, and not the latter (I've gone back and reread the email where you described Phil's comments -- they really are consistent with both interpretations). Especially now that I've had a relook at the TC force-displacement graphs (I had to delete the old ones because of email problems, so it's nice to see them again on the forum!) -- the fact that Phil's referring to "steepness" of the initial bump curve, and the fact that that steepness is evident even on the lowest velocity curve, does seem to suggest it's not an inertial problem (the valves opening more than they should because of inertial overshoot, and perhaps fluttering in a dynamic instability), but rather one of the quasi-steady state response to rising shock pressure.

2) If that's the case, we're back to square one on why the TCs look so similar to the Konis on a single bump, but are so much worse on a prolonged bad road. Two possibilities here come to mind: one is that the single bump you used was somehow different from the "normal" bumps on your bad road; the other is that on the bad road, you're starting to get cavitation effects (which can happen more readily on a cheap shock with less carefully machined valving -- basically if there are any notches, pits, bumps, casting flash, hard transitions, etc on the valve surfaces, those sites will initiate cavitation more readily than will a smoothly machined & polished surface).

3) Then again, maybe the issue is the size of your single bump vs. the size of the rough road imperfections: as I sort of recall, the maximum bumps (on your acceleration graphs) are not that dissimilar between TC and Koni, but the TC had a much busier and rougher "noise" between big peaks. That would mean that on the big hits, both shocks felt more or less similar (consistent with your single bump experiment), but on the smaller stuff, the Konis road smoothly whilst the TCs jittered and bumped almost continuously. That sort of behaviour would make sense, given the curves:

Because the "shin" (the initial steep part of the shock curve) is longer (as well as shallower) on the Koni than on the TC, then (on the smaller bumps) the Koni is working on the linear part of the curve (meaning that the valves aren't blowing off pressure in a big way, so that force is roughly proportional to velocity), whereas the TC is initially hitting its near-vertical force curve, but is then transitioning on and off its very nonlinear "knee". Hence the Koni will be feeling less harsh.

4) As to the importance of the "knee" in the curves -- Peter, those articles were eye-opening!!! I should have thought of it before, but the articles gave me one of those "Ah ha -- of course!!" moments when you realize something that you should have realized much earlier:

A) Up to now, I've only thought of ride comfort in terms of acceleration: the greater the acceleration, the greater the force on my body, and the greater the discomfort. That still holds -- but as we saw earlier, such a perspective doesn't explain why something like the TC is less comfortable than the Koni (after all, the TCs apply less ultimate force than the Konis, so they'll accelerate the car (and our bodies) less, so shouldn't they be more comfortable?).

B) But what I forgot to consider was the rate of change of acceleration -- what the articles you sent describe as "jerk" or "abruptness". If something applies a force to my body, I don't necessarily like it -- but I quickly get used to it. It's like being on one of those amusement park rides that spin a big (30 ft) platter and press you against the outer wall -- there's a lot of force, but because it's continuous, it's really not that bad; you can accommodate it without too much discomfort. But if the acceleration itself changes abruptly, that gets your attention pretty quickly!

Hmmm. How should I describe this?.... Ok, imagine you're a passenger in a car, dozing a bit as you're traveling down the highway, and suddenly the driver slams on the brakes. The initial "impact" of the brakes is the worst part -- you slam against the seatbelt harness, your head rocks forward, and suddenly you're wide awake. But after the initial "slam", you're not uncomfortable -- just concerned. The uncomfortable part was the initial moment of brake application. The thing is, a car doesn't decelerate more rapidly with initial application than it does afterwards, so if all we're doing is measuring force and acceleration, we'd say "What's the problem? The peak acceleration never exceeds X g's....").

Conversely though, if you're travelling down the same highway at the same speed, and the driver (perhaps a trained race driver) smoothly rolls onto the brakes instead of slamming onto them, the initial "slam" is much, much more comfortable. Assuming that the driver rolls onto the brakes hard, the peak acceleration is the same as before (in the slamming case), but the rate at which the acceleration rises is lower, and hence much more comfortable.

Thus in addition to peak acceleration, we need to look at the rate of change of acceleration (a/t). Because the TCs have such a sharp knee at low velocities, even smallish bumps will transition from the high force (and thus high acceleration, given F=ma) part of the curve to the low force (low acceleration) segments, and hence the rate of change of acceleration -- the jerkiness -- will be continually high. In contrast, the Konis might have greater ultimate accelerations, but those accelerations are approached gradually, and hence the jerkiness is much less.

C) So here's a question: does the software that came with the accelerometer permit you to take the first derivative of the acceleration curves? If so, that'd be a quanititative measure of the jerkiness, and it'd be an interesting thing to plot along with everything else.

Anyway, Peter, a very interesting issue -- thanks again for diving into the London bookshops and for digging up all this info. I'm learning a lot, and this is cool stuff(!). Let me know what you think of the above, and also let me know how much of this discussion you want to see posted on the forum; I'm happy to keep it within email, but I'd also be happy to discuss these things publicly. 

Cheers!
- Ceilidh

END OF EMAIL
Postscript: in a subsequent email, Peter brought up an interesting point. As bad as it may feel if a driver suddenly slams on the brakes (instead of rolling progressively onto them), it feels even worse if he "stabs" the brakes and immediately lets go. That's sort of what the TCs do, with their steep initial rise and sudden flattening....
If all the above doesn't make sense, we'll try to circle back and explain it again. In any case, at some point Peter will show some force vs. velocity curves, which are also instructive. Cheers, folks!
- C


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## ewongkaizen (Apr 19, 2002)

*Re: Dampers (pyce)*


_Quote, originally posted by *pyce* »_
Quote, originally posted by ewongkaizen » 
....Slap the accelerometers on the shock on the dyno. That way its easier to compare the "real world" versus the dyno..... 
I do not fully understand how would that help? The damper on the dyno is moved up and down by the crank, so the accelerations (vertical, on the damper) are related to the circular motion of the crank. That thing is so smooth, that is we were to put the accelerometer on there, I guess we would get a very nice sinusoidal line….. I just do not understand how to use later this smooth line in comparison to what the real street accelerations are? Perhaps I did not fully understand your thought, please explain more.


I must admit that I havne had the time to delve deeply into the work you have done. So maybe Im way off base here.
I was thinking that an accelerometer in the car when driving ont he road would only verify (and quantify) the "butt dyno" - i.e. how smooth the car's ride was inside the car
But what is the supensional actually doing?
Consider a bump
Was the car going up and the supension going up too (aka think of a solid suspension)? 
Or did the suspension "mush" until it compressed fully and THEN the car went up?
So to cancel these out one would need an accelerometer on both the "wheel" (i.e. the spindle) and on the car (i.e. the strut top)
Then one could "subtract"the two graphs to get the work that the supension was ACTUALLY doing - not how the car was acting....
I take this cue from the BOSE suspension stuff and thinking about the issue of "noise" and perhaps that what Bose wanted to do was to filter "noise" out of the equation... and thus I borrowed the concept of balanced lines and how those filter out noise on the system.
Also based on the other comment about the "knees" and you comment of the sinusioid and stuff about how how human hearing works - the body is VERY sensitive detector; be "noise" bothers us and "music" does not - why is that? Why does "clipping" and "distortion" bother us more than "smooth" tones?
My theory is that we can detect the dX/dT and that we "anticipate" the curve and when it changes rapidly (think of what a clipped signal looks like in the second derivitive) we are temporarily addled - and thus under discomfort.
So the reason for two acceleramoters ont eh dyno was to get that base signal to compare to the cars signal.
- what feels smooth ont he road?
- what does that look like on the acceleramoter in the car
- what does that look like on the acceleramoter onthe wheel?
- what is the suspension actually doing?
- what are the "knee" points and where are those on the dyno?
To make it easier to compare apples to apples - measure the same thing on the dyno with accelerations (this also allows you to remove bushing squish from the equation...)
Hmm - I think we also need to know the pistion "position" as well as its instantaneous acceleration....


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## pyce (Nov 7, 2001)

*Re: Dampers (ewongkaizen)*

I do now understand what you are saying. This would be necessary if we were a damper manufacturer who has the facilities and the know how of how to modify the dampers as to get to where you are talking about. Ideally we need to have two accelerometer, (which I do not have), two laptops to collect the data simultaneously (which I also do not have)…… therefore the tests are performed on the same street, same speed, same everything as much as we can – this way to have the data that could get from the first accelerometer (possibly mounted on the bottom of the damper) to be as constant as possible. This way we get the second accelerometer to record the result after the suspension did the job, which in fact is what really matters to the person in the car. What you are talking about is exactly what Bilstein should have done before releasing the TC on the market and before even calling it “Touring Class”. Guess their understanding of touring is very different than mine







What we are trying to do here is much simpler than that – the capacity I have is to get several dampers, put them on the dyno then put them on the car and TRY to find a relation between dyno graphs and real life behavior. This way we can learn how to read damper’s dynos and from there we can learn how to eventually modify dampers as to achieve what we desire and eliminate what we do not like…… so, at that point I guess your ideas may come into play. But anyway, I still believe there is no point mounting the accelerometer on the dyno as the result is something I can even draw on piece of paper right now. I the misunderstanding we are having at this point is that to you maybe a shock duno is something that simulates random vertical movements, and in fact there are dynos like that, those big platforms that the car manufacturers have, where you bolt the whole car on it and massacre the suspension for hours and hours….. what we have here is simply motor with crank that provides very smooth acceleration and deceleration and in fact, it is nice to see some absolute values that we are recording and some graphs, but at the end of the day I rally think that the dyno we have is not going to matter much, because who really cares what my or your dampers do on a dyno? I want them to work on the real street, and precisely, on my “unreal” street I have here.


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## pyce (Nov 7, 2001)

*Re: The TC vs. Koni.... (alexb75)*


_Quote, originally posted by *alexb75* »_ .....I do NOT believe any of the tuners out there dared to do similar tests (at least I am not aware of) and no one would be brave enough to publish findings...:

Alex, there is nothing to be brave about this and nothing daring. Everyone can go and purchase a simple accelerometer (that thing is sold for schools for experiments for the kids!! LOL)) and stick it in their car and drive around with a laptop, so other people think he is some sort of secret agent. The only other thing needed is a converter, so you do not need the batteries for the laptop as they can’t last the length of the tests. Come on, let’s do not make this look like more than what it is. Magazines have much better equipment and much more money and time to invest in this, but I guess they are not interested, even if it would be nice if they do decide to give some similar data to all their tests, so people, when shopping for cars, especially luxo cars, could not only see what is the noise level 9that they do publish in db) but can see how comfortable the suspension is compare to another car on the same pre-established path…… Several European magazines had been doing this for years and that is where all this started. I was asking in another thread what kind of device those folks would have been using and Winston came out with the accelerometer and the rest is all above here….


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## ewongkaizen (Apr 19, 2002)

*Re: Dampers (pyce)*


_Quote, originally posted by *pyce* »_I do now understand what you are saying. snip 

Sorry for the confusion - I was kinda few steps ahead of what yer doing now - which BTW is a GREAT service to the VW world and to the automotive tuning world in general....
One thing your graps DO demonstrate clearly - is what YOUR butt dyno confirms to be a "smooth" ride - something which in the past has been quite difficult to quantify - esp when the flame wars start about whose suspension is "better".
SRS has the right approach for the track - whatever reduces the lap times is GOOD.








But for the street - where are the comprimises. Now we have something to comapre.
What we really need is an 8 channel data logger (hmm maybe 5 channels is enuff - as the 4 in the car should be roughly the same - except for chassis twist - wow what we need - even MORE variables to deal with )

_Quote, originally posted by *pyce* »_ the misunderstanding we are having at this point is that to you maybe a shock duno is something that simulates random vertical movements, and in fact there are dynos like that, those big platforms that the car manufacturers have, where you bolt the whole car on it and massacre the suspension for hours and hours….. 

Ah - a 4 post analizer... the better ones even have a moving road under the car and the entire thing fits in the wind tunnel.... but we are not Ferrari F1 with oodles of $$$$ to spend...
Ya might want to scan the last few years of Racecar Engineering _ I think there was an artilce on
- how to read a shock dyno 
- what it can and cant tell you
- the basics of hte "knee" tot he curve and stuff like that....
Possibly a Carrol Smith book has this stuff too?


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## alexb75 (Dec 29, 2002)

*Re: The TC vs. Koni.... (pyce)*


_Quote, originally posted by *pyce* »_
Alex, there is nothing to be brave about this and nothing daring. Everyone can go and purchase a simple accelerometer (that thing is sold for schools for experiments for the kids!! LOL)) and stick it in their car and drive around with a laptop, so other people think he is some sort of secret agent. The only other thing needed is a converter, so you do not need the batteries for the laptop as they can’t last the length of the tests. Come on, let’s do not make this look like more than what it is. Magazines have much better equipment and much more money and time to invest in this, but I guess they are not interested, even if it would be nice if they do decide to give some similar data to all their tests, so people, when shopping for cars, especially luxo cars, could not only see what is the noise level 9that they do publish in db) but can see how comfortable the suspension is compare to another car on the same pre-established path…… Several European magazines had been doing this for years and that is where all this started. I was asking in another thread what kind of device those folks would have been using and Winston came out with the accelerometer and the rest is all above here….


It's not that your tests were fancy or technologically advanced, but it's daring to go against norm and what is believed to be the truth. No one really knew about the actual way different shocks perform, or the way lowering the springs effect the roll center scientifically, or some other tests that you have dared to do (like mating a soft rear spring with stiff front spring)... 
What's daring is to take "tuners" or "testers" or "manufacturer" claims with a grain of salt and go as far as proving them wrong and calling their BS or even teaching them a lesson in suspension design








My hats off to you for your efforts (along with Winston) and vortex suspension forum is much more informative and has much more objective info since you tried to enhance your ride comfort with Bilstein shocks!
Cheers







http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif 


_Modified by alexb75 at 8:11 PM 10-25-2004_


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## j0oftheworld (Apr 25, 2003)

*Re: The TC vs. Koni.... (alexb75)*


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## ewongkaizen (Apr 19, 2002)

*Re: The TC vs. Koni.... (pyce)*

A short 2 page article in RaceCar Engineering - June 2003
p23-24.
Under the Straight Talk column by Conway Young
Article "Damper Pamper"
Discusses the drawback so the "crank" type damper testing rig.
Points out the advances of the "hydrulic" damper testing rig.
Points out issues of Hysteresis (non linear response), how a mechanical damper test rig cant see this and an hydrulic one can.
Raises an isseu as the crank type tester really looks at the "velocity sensitive" nature of a damper. This presumes that we dont use "position sensitve" dampers (whihc as far as I know no one is doing in a coil over package due to overall complexity issues in packaging).
The author works in a hydrulic damper testing consultancy - your ouwn interpetations are warranted.
He does point out that good computer modelling hasnt been done yet.
One item of interest is the comment:
"Consider a simple corner model of a car - a body and hub mass seperated by and ideal spring and damper, witht he hub further attached to the ground via a tire spring. THe damoer us trying to dampen the motion of the body and the hub. THe higher frequency oscillations will always be damped more than the lower frequency body motion, hust the opposite of what you want 0 a well damped body and a loosely damped hub."


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## pyce (Nov 7, 2001)

*Re: The TC vs. Koni.... (ewongkaizen)*


_Quote, originally posted by *ewongkaizen* »_A short 2 page article in RaceCar Engineering - June 2003
p23-24.
Under the Straight Talk column by Conway Young
Article "Damper Pamper"
Discusses the drawback so the "crank" type damper testing rig.
Points out the advances of the "hydrulic" damper testing rig.
Points out issues of Hysteresis (non linear response), how a mechanical damper test rig cant see this and an hydrulic one can......

Would you enlighten us up some? Thanks.


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## ewongkaizen (Apr 19, 2002)

*Re: The TC vs. Koni.... (pyce)*


_Quote, originally posted by *pyce* »_
Would you enlighten us up some? Thanks.

I dont have the article in the office with me tonite...
The article was rather short and and thus lacking in details...
First - whats Hysterisis
http://www.lassp.cornell.edu/s....html
BTW - Hysterisis may also have some reation to the Koni/TC issue that Ceilidh raises a few posts back
Off the top of my head (will edit later) the author (who btw was a cunsultant for the "better" type of test rigs and thus may have some hidden bias) claims that the crank type of test rigs will show a "linear" response where the hydrulic rigs will show an response curve that has a "response" envelope.
Pyce - IM me with an email or snail mail so I can get the article over to you.
The main point of the article (that damper response is the opposite of what we really want) was most enlightening - that we want "hard" at low piston velocities and "soft" at high velocities - to a point... 
The problem is that hydrulic damper valves are SOFT at low velocities (aka roll on a car) and HARD at high velocities (hitting a kerb)...
What we really want is HARD in roll and SOFT on the bumps.
There is some way to do this with hydrulic lines that go between the left and right sides of the car as well as front and back (pitch issues). There was another Racecar Engineering article where one of the Rally Teams used a rather simple setup with valves and pistions (as the piston moved off center it opened up holes that passed the fluid into the reserviours of hte other shocks...)... This addressed ptich and roll issues seperately from the individual wheel dampening issues....
Of couse - active suspension can solve this too.... 

--- morr notes from the article
What we really want is "freqency related" damping.Right now there is no workable way to do this (EWong: unless thats what Bose does?).
Ohlins that possibly stands out as tking the most sc ientific approach...
The best intuitive design must go to Kees de Kock at Koni...
(note: Koni uses shim packs not needle valves for adjustability)
Dampers have historicaly been tested on a mechnaical damper dyno.
These have an electric motor with a simple mechanism to produce axial sinusoidal motion in the same way a cranksahft links pistons.
To test a damper they run at a fixed speed for a few cycles, the maximum force and velocity measured ( in bump and rebound). The speed is then regularly increased and the force and velocity measurements are repeated giving a graph in Figure 1 (sloped curve on froce x velocity graph, )
The results, precise points on a force agains velocoty graph can hidea multitude of damper (and eve dyno) abnormailties.
However a single cycle test with a refined hydrulic dyno, measuring force and velocity continiously gives a corrected insight into the damper. The same damper is tested on a hydrulic dyno produced Figure 2 (similar graph as Fig 1, but the line gets "fat" (aka has variance of force) in a certian mid range of velocities in this case in the neg force values where the velocity is neg)
(close)
.... there has been little attempt to understand what dampers are tying to do and how it might be best achieved.
EWong: so maybe Pyce et are are breaking new groud in attempting to UNDERSTAND?


_Modified by ewongkaizen at 5:15 PM 10-28-2004_


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## phatvw (Aug 29, 2001)

*Re: The TC vs. Koni.... (ewongkaizen)*


_Quote, originally posted by *ewongkaizen* »_
Of couse - active suspension can solve this too.... 

Active suspension is so cool. Have you guys seen that Bose thing?
Your suspsension could double as sub woofers, so you don't have to upgrade your crappy Monsoon system lol!


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## pyce (Nov 7, 2001)

*Re: The TC vs. Koni.... (phatvw)*

Speaking about active suspension.... we had the luck to be in Paris just few weeks ago during the Paris Autosalon and there was this prototype from Bridgestone. You could press a button and actually watch the simulation. Guess things like this will really revolution the world of small cars. There were some nay other interesting things ot share, but I guess we will go way too much off topic.....


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## pyce (Nov 7, 2001)

*Tc vs. TC and OE vs. OE ......*

Went to the dyno tonight for another round. Couple of interesting findings here:
1. Dynoed an OE damper from Golf TDI and one from Jetta TDI, so we have same engine, same trim, same rims/tires, just basically one is a Golf and the other one is Jetta. We know from the color codes from the springs, that both cars use different springs, even if we do not know yet exactly how different they are. Well, tonight it came out (the outcome of the dyno will be posted tomorrow) that the dampers on the Jetta are quiet different than the dampers on the Golf. Meaning, the Golf has significantly softer compression and rebound! So, we knew they have different part numbers, but we did not know by how much (if any) they differ. Now we found out the difference is there and it is quiet substantial if we look at the graphs. At this point it will be very interesting to see what are the GTI dampers or perhaps dampers from Jetta Wagon........ More on this tomorrow when the graphs come out....
2. The Bilstein TC Sport were tested side by side with the Bilstein TC Standard. If you all remember, various sources talk about the Standard being 10% stiffer than OE and the Sport being 20% stiffer than OE...... Comes out (according to the graphs!) that the Standard actually have even higher compression (not by little!) than the Sports, but significantly smaller rebound. I guess we have ot test them with the accelerometer, but I really do not see how the Standard is going to be more comfortable than the Sport with a graph like this........
More tomorrow...


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## darisd (Dec 20, 2002)

*Re: Tc vs. TC and OE vs. OE ...... (pyce)*

What about the Bilstein HD? I thought they had different internals than the TC... or am I wrong?


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## ewongkaizen (Apr 19, 2002)

*Re: Tc vs. TC and OE vs. OE ...... (darisd)*

updated previous post on the damper article....


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## dohc (Sep 28, 2001)

*Re: Tc vs. TC and OE vs. OE ...... (darisd)*

The suspension forum has really progressed.
I usaully don't even look in here because most of the time its just opinions with no technical data.
I've been designing, testing and building shocks and struts for 4 years now (military and very large applications), and have access to all kinds of equipment, but haven't ever had the time to post anything like this as far as relatign to VW's or even cars for that matter.
Good work guys, you have now inspired me to do some testing when I get the chance. http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif 
If you have any questions, please ask.


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## pyce (Nov 7, 2001)

*Re: Tc vs. TC and OE vs. OE ...... (dohc)*


_Quote, originally posted by *dohc* »_.....If you have any questions, please ask.

If we have any questions? This whole thread is a giant question of how to really tune these things!







I am glad someone with such experience like you decided to stop by and I hope that you can give some light here, so we first understand in more detail how these things work, so this way we can identify where the problems are and why damper "A" behaves the way it does and what makes damper "B" a better one, etc.... My personal plan is to open one of the OE dampers and see actually how exactly it is done. We all know the principle behind, but I want to compare technical solutions between the various dampers, so we have an idea what works better and what not. As had been said, people generally do not realize how much the damper gives to the whole suspension assembly, but if more than one damper is tried on the otherwise same car, then the difference could be noticed and then the user realizes that dampers are very important and a lot could be done with them..... Anyway, tell us more about you, share some knowledge, please. One thing I would like to know for sure is whether we are on the right path here and how seriously we should take those mechanical dyno results? Also, what do you think about "Ceilidh's" comments and Phil's comments about the TC Sport's curve in compression? I assume you read all the stuff above and if you have not, I would be glad if you can spend some time to do so. Thanks....


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## pyce (Nov 7, 2001)

*OE vs. OE ...... graphs*

OE Monroe from a Golf TDI, from 2.00 in/sec to 20 in/sec. Did not want to waste time and make ten graphs, comparing them at every speed, because the results could be seen (if anyone cares) when viewing the following graphs with the one posted earlier (the OE Boge-Sachs) Jetta TDI….








But at least the 30 in/sec speed was done on one page, so it can be compared (below) so we get an approximate idea of how different they are. At this point I guess that for Golf owners the real “about 10% upgrade” would be actually to get Jetta dampers….. Perhaps the used Jetta dampers on the Classified just went up some! LOL







So, here we have it:








Will try to post later the TC “Standard” graphs…


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## dieseldorf (Sep 26, 2000)

Peter, great stuff !! Very interesting to see real "data" !
; )


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## alexb75 (Dec 29, 2002)

*Re: (dieseldorf)*

Amazing....
and this begs the question... WHY? 
Why would VW engineers get one damper for Golf and another one for Jetta? Is it because of weight?
Are we sure that the Jetta shock doesn't come with some Golf?! Does it depend on the year? Has it been just a supplier change? Was it just luck... it really could be!
I recently changed my CAT/DP and I realized the new one looked different than the old one... so I had to dig in deep (with little help from the dealer) to find out what's the difference. I found that the VWs made in Brazil (mine) had different CAT/DP than the ones made in Germany as they were supplied by different companies. But, the German one was a better (or preferred CAT) and for replacement you can only get the German version! 
So, would something like this hold true for shocks as well? We all know that same cars and tranny's have had different colored springs, so I guess that OEM shocks could be the same as well?! Couldn't they?


_Modified by alexb75 at 1:56 PM 10-28-2004_


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## Boundless (May 23, 2004)

*Re: (dieseldorf)*

Incredible data.
Lots to think about.
http://****************.com/smile/emthup.gif


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## pyce (Nov 7, 2001)

*TC vs. TC ....*

Sorry for the delay on the TC vs. TC graphs…. Here we go, on the first graph you can see the Force vs. Displacement for the Bilstein TC “Standard” from 2.00 inches to 20.00 inches per second (in/sec). The shape of the lines looks very, very similar to the ones we got from the TC “Sport” just the values are little bit different….








Here is the interesting part. When compared to the “Sport” at let’s say 18 in/sec, we can see that there is clearly more compression and significantly less rebound….but at the same time, the beginning of the compression (the top left quadrant) is not as steep as the one offered by the “Sport” so perhaps this damper, even if it has higher compression values, may actually be slightly smoother than the TC “Sport” brother, but I would not expect an impressive improvement. Anyway, the accelerometer will tell the story later ….








Now, here we come with the questions (and I wish Bilstein can read this and answer):
1. By now we know that these two dampers are sold as the “TC Standard” being 10% stiffer than stock and the “TC Sport” being 20% stiffer than stock. At least this is the message I get from any vendors…… So, I am curious to know how exactly was established that these are 10 and 20% stiffer than stock? According to which values from our graphs? Where these 10 and 20% came from?
2. What does really “10% stiffer” means when we talk about dampers? Is it comparing values from the graphs at specific points, like for example the highest velocity point or is it vertical “G’s” that are compared and those numbers come out?
3. How is it that the “Sport” is sold as stiffer (by 10%) than the “Standard”, but the graphs do show that the “Standard” has more compression (where I guess the “stiffness” kind of comes from to begin with).
4. We are slowly finding out that VW tuned separately almost every specific model in a different way, there are differences in the damper’s tuning even on the same car with the same engine but with few percentage front to rear weight difference… At this point it is clear that the aftermarket common of the shelf dampers in the range of 500$ per set are not really “tuned” to match each and specific body, engine, trim, but are kind of generalized for the make and model. So, how do we do the matching? How do we know which TC would suit a specific body and trim? What spring rate were these tuned for? Or is it just _“slam the suckers in, get it stiff, so you feel sporty dude and enjoy life as it is short”_ approach?
I would be extremely happy if anyone could spend some time and share some light on this, so we all learn something here. Thanks.


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## Ceilidh (Jan 7, 2004)

*Re: TC vs. TC .... (pyce)*


_Quote, originally posted by *pyce* »_....We are slowly finding out that VW tuned separately almost every specific model in a different way, there are differences in the damper’s tuning even on the same car with the same engine but with few percentage front to rear weight difference… At this point it is clear that the aftermarket common of the shelf dampers in the range of 500$ per set are not really “tuned” to match each and specific body, engine, trim, but are kind of generalized for the make and model. So, how do we do the matching?....


Nice work as always, Peter....
A related question is: How does one reproduce the original factory ride when the OEM shocks wear out? Will the dealership really stock the myriad of subtly-different shocks that were originally specced for different years, models, and trim packages? Or will one's replacement shocks be some similarly generic "OEM" part?


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## alexb75 (Dec 29, 2002)

*Re: TC vs. TC .... (pyce)*

Interesting... another great post.
I think most tuners are mostly concerned about rebound and as we see here Sport rebound values are like 20% more than standard, while compression is less (have no idea why)?!
I was told by Mike (Tyrol) that for performance rebound was more important... hence rebound adjustments are more useful than compression. 
I totally agree that most tuner shocks are built for all similar platforms and not as specific, but to be quite honest, I don't really think anyone can afford to do a complete lineup of different shocks for all different platforms/engines... Can you imagine how many different combinations would we have? Specially if you include all other manufacturers. VW can afford to do that as they sell millions of cars, shock manufacturers do basically what makes business sense. 
The only way around this, would be an adjustable shock (like Koni's) with some recommended setting for each platform (to save us time and effort). I was very disappointed that there was absolutely no recommended setting or anything like that by Koni (or Neuspeed), even calling their office and talking to smilingly techies didn't help. I was just left to experiment, kill my back and maybe risk crashing to find proper setting!!!


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## f1forkvr6 (Jun 10, 2002)

*Re: TC vs. TC .... (alexb75)*


_Quote, originally posted by *alexb75* »_I was told by Mike (Tyrol) that for performance rebound was more important... 
A damper must control the energy released by a compressed spring. When spring rates increase, rebound control must also increase. If you can control rebound, you can use spring rate to slow/control compression. This is why most off-the-shelf dampers control/or are adjustable in rebound rather than compression.


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## Ceilidh (Jan 7, 2004)

*Re: TC vs. TC .... (pyce)*

Hi Peter,
1) Little request on the graphs: whilst the raw Force vs. Displacement curves have the most information, most people here (I would expect) aren't used to interpreting them, and are more familiar with the common Force vs. Velocity curves that are seen on many websites (including Koni's). Could you maybe post some of those plots in company with the F vs D graphs? That way we could show the "knee" that's causing discomfort on bumpy roads, and the "fuzzyness" of the Koni curves would show how soft they can be on initial impact.
2) Also, Chris (f1forkvr6), you (as always) raise a very good point about the stiffer rebound damping on the TC sports being important for body control, but I think what's puzzling Peter is the increased compressional damping on the non-sport, ordinary TC. As you know, the compression damping on a passenger car is usually set at a value that's high enough to control the unsprung weight but low enough to minimize the initial upset due to bumps, after which the rebound is set to control body motion.
What's strange about the TC's is that the non-sport TC, which is presumably on a car with smaller wheels & tires and hence less unsprung weight (since most people who "upgrade" their wheelsets wind up adding a lot of unsprung weight), and which is presumably optimized for ride comfort, actually has a higher rate of compressional damping.
3) Peter's overall experience with the TC has not been overly great (if I understand him correctly): whilst the TC is often mooted on these threads as a softer-riding, cheaper alternative to the HD/Sport or Koni Yellow, in fact Peter has found that the TC rides more harshly than a Koni Yellow set at 1/4 turn (at which point the Koni has extremely good body control). The question is, Why?
Besides the strange TC vs. non-TC compression levels (which I recall are both still lower than the Koni's -- is that correct, Peter?), the TC appears to have a sharper "knee" in the Force vs. Velocity curve. This sharp knee was noted by the fellow who did Peter's dyno tests, and who correctly predicted on the basis of the knee that the TC would ride poorly on the roads Peter has to drive on. Problems with the knee are also hinted at in the Milliken vs. Milliken tome, and in London Peter found a textbook that discusses the knee in more detail.
4) ewongkaizen, I think this is where you might find things a bit interesting, particularly with regards to the RaceCar Engineering article espousing stiff damping at low piston velocities and softer damping at high piston velocities.....
One fairly odd thing about the Koni vs. TC (which I'm hoping Peter can show in a Force vs. Velocity graph) is that even when the Koni has much stiffer damping than the TC (including at high piston velocities), it still feels more comfortable. What we're generally taught -- in many publications, not just RaceCar Engineering -- is that bumps cause high piston velocities, whilst body motions are associated with low piston velocities. Thus the conventional wisdom is that we should have a very steep F vs V curve at low velocity (which maximizes damping at low piston speeds), and then a much flatter curve (which minimizes damping) at the high velocities that characterize bumps.
This is the curve that the TC has. But the TC is not very comfortable. So what's going on?
From what we can gather (from the dyno guy's comments, and from the textbooks Peter has found), the problem is that firm damping at low speeds and soft damping at high speeds is hard to accomplish without a "knee" or kink in the F vs V curve, where the curve abruptly changes slope from steep to shallow. And that knee causes problems because as the shock piston velocity increases or decreases and crosses the knee, the damping forces abruptly alter in a very non-linear way. This non-linearity causes "jerkiness", which the texts define as the rate of change of acceleration, and is presumably the source of the discomfort.
5) Or, put another way: it's not enough to have firm damping at low piston speeds and soft damping at high piston speeds; it's also critical that the transition between the two regimes be as smooth as possible. In fact, it is sometimes better to have firmer damping at high piston speeds, if that firmness makes for a smoother curve. This smoothness is a hallmark of the OEM damper, but the Koni does a fairly good job of reproducing it at higher damping levels, and apparently that is one reason why it's so comfortable when compared with the other performance shocks.
6) The final curious thing (which Peter will eventually show, when all the graphs are complete and posted) is just how huge an effect shocks have on ride comfort, and how subtle the differences are between a great shock and a shock that is merely good. Some of Peter's accelerometer results (I've seen them via email) show that the ride comfort difference between a Koni and a TC is as great as that caused by an 8psi increase in tire pressure (which is pretty big!), with the Koni being more comfort. But when you look at the TC vs. Koni shock curves, the differences are fairly subtle -- surprisingly so, in fact.
In short, it's becoming more evident why good shocks cost as much as they do, and how important it is for people to carefully research shocks and choose the one that best fits their needs. Dick Shine has often argued that many aftermarket tuning kits achieve improved handling solely because of the shocks (i.e., that the improved damping masks the big problems caused by the lowered or too-soft springs); those arguments are made on the basis of performance. What Peter's showing here is the other side of the coin: if the wrong shock is chosen, the ride comfort is going to be unacceptable, even though the spring might be just fine.
Anyway, that's the state of things right now. Please do chime in when you see the graphs, everyone -- we're definitely in learning mode here, and the more we can figure this out, the better.
Cheers!
- Ceilidh


----------



## ftillier (Nov 30, 2002)

*Re: TC vs. TC .... (Ceilidh)*

fantastically fascinating thread. I should have gone to bed a while ago, but couldn't get away. Great stuff, thanks for sharing with us.
- Fab


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## ewongkaizen (Apr 19, 2002)

*Re: TC vs. TC .... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_
From what we can gather (from the dyno guy's comments, and from the textbooks Peter has found), the problem is that firm damping at low speeds and soft damping at high speeds is hard to accomplish without a "knee" or kink in the F vs V curve, where the curve abruptly changes slope from steep to shallow. And that knee causes problems because as the shock piston velocity increases or decreases and crosses the knee, the damping forces abruptly alter in a very non-linear way. This non-linearity causes "jerkiness", which the texts define as the rate of change of acceleration, and is presumably the source of the discomfort.


My read of the RaceCar Enginnering article was that the "non linearity" that you speak of (the Jerkiness") is the "hysterisis" that the article refers to. Thus the claim for the "hydrulic" test righ which can detect this while the "mechanical" dyno can not.
The article IMPLES that the use of needle valves has something to do whith this (aka twin tube) as opposed to the Koni method of a "stack".
The position sensitive shock attempts to address this by creating "ranges" where the stack valve changes dramatically (by bypass tubes for the oil to flow around)
Much of shock tech has been in the last 20 years.
IMHO - alot was learned in the early 1990s byu off road racers which long travel, high heat and HUGE shocks. Those guys (Fox, King) later went on to places like Penske Shocks etc... and transferred theior knowledge to the "race car" world. Their contributions became even more important as active was banned.


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## Ceilidh (Jan 7, 2004)

*Re: TC vs. TC .... (ewongkaizen)*


_Quote, originally posted by *ewongkaizen* »_
....RaceCar Enginnering...the "non linearity" that you speak of (the Jerkiness") is the "hysterisis" that the article refers to. Thus the claim for the "hydrulic" test righ which can detect this while the "mechanical" dyno can not.
The article IMPLES that the use of needle valves has something to do whith this (aka twin tube) as opposed to the Koni method of a "stack"......

Hello Ewong,
Thanks very much for the paraphrasing of the RCE article; this is the sort of info that will really help up fill in the holes in our understanding! I think the article is referring to something a little different from the "knee" -- but it's something that Peter & I have been puzzling over for a few weeks, and the info you provide is extremely interesting!
1) First off, about the "knee" vs. hysteresis: "hysteresis" is an engineering/physics term referring to a system's (e.g., an object's, a mechanism's, a material's) inability to return to its original state after being stressed, strained, or perturbed. Things with hysteresis are non-linear, but not all non-linear things have hysteresis.
To explain: the "knee" referred to earlier is not a result of hysteresis -- it's simply the non-straight line (hence, "non-linear") shape that the velocity vs. force curve takes as the shock transitions from low velocity to high velocity. That non-linear, "kneed" shape is evident even in the steady-state graphs that the simple mechanical tester produces, and is one cause of the jerkiness discussed earlier.
2) But what's really intriguing is your report of valving differences between a normal twin-tube and the Koni (also a twin-tube, but considerably more expensive and apparently (judging from the article) of a different design). When we couple the valving difference with the "hysteresis" mentioned in your article, we come up with something very interesting indeed:








3) (Peter, can you post up your accelerometer plots of the TC vs. Koni on one bump, and contrast that with the accelerometer plots taken on the long bumpy road? I think this is a good time to show everybody -- thanks!)
4) ewong, this is the neat thing: a few weeks ago, I asked Peter to drive his instrumented car over a single sharp bump, so that we could see the differences between a TC and a Koni without the distractions of general rough-road busyness. He very kindly did so, but the results were fairly boring: when he overlaid the accelerations produced by the Koni over those generated by the TC, the plots almost coincided -- that is, the TC is about as comfortable as the Koni on a single bump.
(Note, by the way, that the Koni is a fair bit stiffer than the TC -- the fact that the two shocks are nonetheless about the same, comfortwise, indicates the importance of the knee/ slow initial action/ etc. evident in the force vs velocity curves...)
Anyway, what Peter did next was to drive his instrumented car over a continuously bumpy road, and those results were pretty stunning: whilst a TC is about as comfortable as a Koni on an isolated bump, on a closely-spaced series of bumps, it's much, much less comfortable....
5) This is hysteresis!! On a smooth road with isolated bumps, the TC has a chance to return to its normal state, so that it's always at Square One when it hits a bump. But when there are many closely packed bumps, it doesn't have a chance to return to "normal" -- it hits a bump, starts to recover, and then hits another bump before it's really "ready", and with each bump things get more and more out of kilter and uncontrolled.
6) Peter's dyno guy ("Phil") hinted at this effect, but we were unsure (from the words used) what was causing it.
7) Anyway, if an inexpensive twin-tube shock uses a needle valve while the Koni uses a stack, then that would explain everything. Needle valves have inertia: the needle is attached to a holder and a spring, all of which have mass and hence inertia, and that inertia means the valve doesn't always open as rapidly as it should, and (more importantly) it doesn't always close as rapidly as it should. (Peter, remember our discussion earlier? -- this is a potential key!). As a result, the hydraulic pressure inside the shock tends to overshoot up and down, and on a continuously bumpy road, the result is that sometimes the valve is closed when it should be open (making the shock too stiff, so it transmits jolts into the passenger compartment), and sometimes it's open when it should be closed (leaving the sprung and unsprung masses uncontrolled, so things are free to jump and rattle around).
(In fact, if there's a lot of hysteresis, you'll be forced to jack up the compression damping higher than you'd really want, just so you can control the unsprung masses -- maybe that has something to do with the strange TC compression curves.....)
By contrast, a valve stack (if it uses a bunch of belleville washers stacked together) has very little inertia, and thus very little hysteresis. Hence even on a rapid series of bumps, the valves only open as much as they're intended to, and they adjust back to "normal" so rapidly that they're always ready for the next bump. Thus the comfort on a single bump will be about the same as that for a continuous series.
8) In short, it'd be really interesting to (as Peter plans) open up some shocks and see their internals. If the TC and Koni have fundamentally different valving (on the primary blowoff valves -- there are probably some needle bleed valves elsewhere in the Koni system...), then we have an explanation for what's going on (and if not, then we're back to Square One again.







).
Thanks again for the article, ewong -- keep 'em coming!
- Ceilidh


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## alexb75 (Dec 29, 2002)

*Re: TC vs. TC .... (Ceilidh)*

Thanks Ewong and Winston in trying to explain all this. I have had similar experience but with Bilstrein Sport (mono-tube). 
In my experience with Koni and Bilstein Sprot (different than TC) I have noted that on a single bump, at certain Koni stiffness setting... they could react almost exactly the same. However, on a stretch of road with many bumps, the Koni is by far more comfortable. Like whenever I hit a stretch of road with bumps on Bilstein... I could take the frist couple of bumps, but then had to slow the car down considerably to go over the rest. With Koni, if the first couple of ones are bearable the rest are as well.


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## Ceilidh (Jan 7, 2004)

*Re: TC vs. TC .... (alexb75)*


_Quote, originally posted by *alexb75* »_....I have had similar experience but with Bilstrein Sport (mono-tube). ....on a single bump, at certain Koni stiffness setting... they could react almost exactly the same. However, on a stretch of road with many bumps, the Koni is by far more comfortable. Like whenever I hit a stretch of road with bumps on Bilstein... I could take the frist couple of bumps, but then had to slow the car down considerably to go over the rest. With Koni, if the first couple of ones are bearable the rest are as well. 

Very interesting, Alex -- the Bilstein Sport is supposed to have a valve stack (as opposed to a needle valve), so if you're finding hysteresis effects there too, things get even more complicated!
Hopefully somebody will send an HD or Sport to Peter (if nobody has done so yet), so we can get some date there too.
Thanks Alex -- all the best! - C (W)


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## alexb75 (Dec 29, 2002)

*Re: TC vs. TC .... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_
Very interesting, Alex -- the Bilstein Sport is supposed to have a valve stack (as opposed to a needle valve), so if you're finding hysteresis effects there too, things get even more complicated!


I think the reason for Bilstein sport behaving that way is different. It could be the high pressure gas and the Auto valvin thing. I once read a review that some guys on M3 tried dropping weights on Bilstein sport, the frist couple of times, the weight made the shock compress a bit, but then it got so stiff that it didn't move at all!!! 
Peter also can chime in the way Bilstein sport feels like.


_Modified by alexb75 at 4:13 PM 10-30-2004_


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## ruking (Apr 4, 2003)

*Re: Dampers (Shocks) .... little bit more about them (pyce)*

Peter,
Keep up the good work! It is refreshing to be able to look at shock/strut selection from a more technical view! So it is good to get the 411 also on the bang for the buck equation.
One of the things in the market place that might be more apples to apples, so to speak would to be to compare the Koni's "red's" (non adjustable $294, for the Honda Civic variant) to the (obvious non adjustable) Bilstein line. Sachs produts are available after market (329) also'

As you are undoubtably aware, a cursory look at adjustables also include (for our VW's) KYB AGX (427) Tokiko Illumina (469) Koni yellows (540) (sorry if I left out any others) So a logical question is given measurements how would one rank order the adjustables and the all important question: why?
So independent of the VW testing, folks in the Honda Civic/Accord, rate the KYB AGX's as great price/performance value, followed by the Tokiko Illumina. Koni's are of course very good but also are inserts(for the fronts) and require some modification to fit correctly/well, and cost more (540)
I realize that you are building a baseline, and I am in no way advocating endless testing.
Thanks for the great work!



_Modified by ruking at 7:27 PM 10-31-2004_


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## apr2009gti (Sep 25, 2003)

so for a guy that has some shine springs in a box and needs to order some shocks. No racing just need good one.
Are the Konis sports still the best for comfort?
01 golf 2dr TDI


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## pyce (Nov 7, 2001)

*Few things....*

Quick post here, just wanted to clear up few things...
The letters (e-mail) you all hear about from Winston and the not-posted graphs, etc are NOT an attempt to hide something from all of you. The whole reason we exchanged several e-mails before this topic even started is because we wanted to decide what is the best way to present this data, how to organize it, and most of all, to have some idea of how to read it. It was all done for the benefits of this thread, so we can talk in extend of the thread for the miscellaneous and then make a "concentrate" of everything together and post it here, so this thread does not go 30 pages and we all do not get lost in there. At this point I have more than 100 graphs, but who would really like to see one hundred pictures in a thread? Let's think about people with modems, slow lines or even limited time..... So, the graphs Winston is talking about are coming, I will post them on Monday as do not have time now to go through organizing them. It is not just about copy-paste stuff, we want to make them easy to read and have all same size, etc, So, it takes some work. Please everybody, be patient and it will all come out. As you can see, we are using the graphs done in the 18 in/sec speed. Why is that? Well, simply because was around the middle of the range and it is pretty visible what is going on there. Now, if anyone wants to see all the remaining graphs (from 2 in/sec to 30 in/sec) just let me know and I will post them, no problem, but they would look pretty much the same and I was just not seeing a reason to "load" more pictures on the already otherwise heavy thread. Therefore the 18 in/sec kind of made it here and it is the only comparison you all see..... The next thing is - why Displacement vs. Force instead of Force vs. Velocity? Well, it was either this or that first, had to pick one and post it, so it was the Displacement graphs. The Velocity will follow on Monday. Then the graphs about tire pressure (32 PSI vs. 40 PSI) on the same car (that Winston mentions above) are somewhere on page one. They all look similar as the colors are green and red, but I tried to put some titles in the lower right corner, so to differentiate them. Sorry about the colors, but the software picks them, starts with red and goes then with green and then blue and orange and so on..... of course, we can change them in Photoshop, but I want to keep everything as original as possible, so we focus on the shapes and colors do not play role in judging what we see. The book that he is talking about is something I found in a book shop and it was thick stuff that was priced about 90$, so I decided to skip the purchase, but with permission of the owner of the store I took some pictures from several pages, stuff that I thought would be helpful to all of us to understand more the data we got. Those few pages are still on the server and you all feel free to go and read them, it is an important and interesting read. Here are the links, page by page and this is all I have. I will later on try to find this book form a cheaper source and will purchase it, some more details will come out, but here we have somehow the most important wrapped in few pages:
Page 01
Page 02
Page 03
Page 04
Page 05
Page 06
Page 07
The rest will come on Monday. You all have a great Sunday, I am going to make mine now


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## alexb75 (Dec 29, 2002)

*Re: Dampers (ruking)*


_Quote, originally posted by *ruking* »_One of the things in the market place that might be more apples to apples, so to speak would to be to compare the Koni's "red's" (non adjustable $294, for the Honda Civic variant) to the (obvious non adjustable) Bilstein line. Sachs produts are available after market (329) also'

As you are undoubtably aware, a cursory look at adjustables also include (for our VW's) KYB AGX (427) Tokiko Illumina (469) Koni yellows (540) (sorry if I left out any others) So a logical question is given measurements how would one rank order the adjustables and the all important question: why?
So independent of the VW testing, folks in the Honda Civic/Accord, rate the KYB AGX's as great price/performance value, followed by the Tokiko Illumina. Koni's are of course very good but also are inserts(for the fronts) and require some modification to fit correctly/well, and cost more (540)


that would be a little of a tall order for our buddy here. I think we all should get on with the tests and try to help out with parts that we have and try to expand the effort. 


_Modified by alexb75 at 5:24 PM 10-31-2004_


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## ruking (Apr 4, 2003)

*Re: Dampers (alexb75)*

Yep I agree, I sent him the standard Bilstein TC, which dyno results are graphed in this thread.
So more to the point is: how the Koni adjustable shocks would look at say instead of 12%, say more toward the middle 25-50% (harder setting)


_Modified by ruking at 1:34 AM 11-1-2004_


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## Ceilidh (Jan 7, 2004)

*Re: Dampers (ruking)*


_Quote, originally posted by *ruking* »_....how the Koni adjustable shocks would look at say instead of 12%, say more toward the middle 25-50% (harder setting)....

Just a background note for everyone: the 12.5% (1/4 turn) Koni setting turns out to be the most comfortable setting at the rear (when used with stock springs), and is the setting both Peter and I independently converged upon in the search for a reasonable ride/handling compromise. Hence it seemed like a good place to start.
Cheers, people!
- C


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## ruking (Apr 4, 2003)

*Re: Dampers (Ceilidh)*

Yes for sure this is evident on the thread as well as discussions with Pyce. Also for the purposes of illustration, the Koni Yellows have a "two turn" adjustment, hence 8 x .25 turns = two turns or 12.5%= 1/4 turn!!?? If I am incorrect here, please correct the situation. Perhaps I am jumping the gun a bit in light of the base line being established on a stable of shocks. 
My thoughts at the time of asking is when you start to put combinations together such as Pyce's 32 psi road travel graph and chassis and the 40 psi, graph, and testing for the delta in ONE VARIABLE: in the two graphs case TP of 32 vs 40 psi. (this is really the basis for clean scientific method) sooner or later there is still some methodology for now a slew of product selection: other than I like it, not, feels good/feels bad, this is cool, not cool etc!? So keep up the good work and theorizing! I shall hold my horses so to speak! (pun intended)











_Modified by ruking at 8:12 PM 11-2-2004_


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## pyce (Nov 7, 2001)

*Single Bump comparo (TC vs. Koni)*

Here are the graphs done on a single bump (a short but tall speed bump actually) at several speeds, posted in the lower right corner of each picture. The interesting part to note here is that the Koni are still set to 12.5% stiff (1/4 turn) which from the dyno shows us how this setting offers much less rebound than the TC Sport. At speeds of 6 mph the TC Sport has the second spike after the bump slightly higher than the first, which shows that there is little less rebound on the TC. At 7 mph thought, the picture changes quiet dramatically, for some reason, and the second spike of the TC is considerably higher than the first, showing at the same time how the Koni behaves on the same bump and same speed. At 10 mph, things go to almost identical behavior. 
























Then we did go over another bump, that was looking slightly different, little bit taller and with slightly sharper crest….. On the slowest speed the Koni this time behaved like there was less rebound (comparing the first spike with the second), but then things slowly changed and by 10 mph shows again slightly better control. For those of you wondering how exactly were the 6, 7 and 10 mph speeds achieved and what kept the consistency – the 6 mph is first gear in idle, and for the other two the idle was “lifted up” via vag-com for the tests. 
























Anyway, as Winston said, pretty boring data….. Do not know you, but I have hard time to draw any conclusion from just these six pictures above. Perhaps those two dampers really behave in a very similar manners (and it feels like that!) when it comes to single bump situation. At those relatively low speeds I really could not notice any substantial difference that deserves to be noted here. Anyway, last Sunday I put back the stock dampers on the car and perhaps next weekend will get some data from what this car does on the same bumps and speeds, so having a third graph in there may eventually start showing more light.


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## pyce (Nov 7, 2001)

*Force vs. Absolute Velocity (18 in/sec)*

Here is the long waited for Force vs. Absolute Velocity graph. Again, we will use the 18 in/sec, so the colors are the same as the Force vs. Displacement from the previous posts. The graph looks little bit “messy”, not as clean as the one we are used to see on some manufacturer’s web sites, and the reason is that he clean graphs do show basically the beginning of the compression (till max speed is achieved) and then the beginning of the rebound (till max speed again), so we see two very clean lines, one that goes from zero to top right and one that goes from zero to bottom right. They have basically eliminated the “return” lines, those from max speed back to zero, that are also shown here and that makes little bit confusion, but I will try to clean them and post it again later as a “one line” graph….. Just wanted to show the original data first, so someone would not think that it is “doctored”


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## f1forkvr6 (Jun 10, 2002)

Peter - 
You are doing a yeoman's duty with this analysis. Thank you!


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## alexb75 (Dec 29, 2002)

*Re: Force vs. Absolute Velocity (pyce)*

What's most interesting to me is that Koni behaves very similarly at higher speeds when softest or stiffest?! It is however much different at lower speeds? 
Can someone explain to me what does this mean in real life?
EDIT: Also, doesn't this graph show that bump changes in Koni and the stiffer the shock, the bump's higher (the negative values)? 


_Modified by alexb75 at 9:29 PM 11-3-2004_


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## alexb75 (Dec 29, 2002)

*Re: Force vs. Absolute Velocity (alexb75)*

Now, compare that graph to this








The KW V2 uses Koni (but they claim differently tuned)... it doesn't look much like the graph we got?!
BTW - the 0.5 m/sec is 12.7 inch/sec


_Modified by alexb75 at 12:49 AM 11-4-2004_


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## pyce (Nov 7, 2001)

*Re: Force vs. Absolute Velocity (alexb75)*

Wanted to step back little bit here and show something that will help, perhaps, realizing the accelerometer’s graphs better. Should have done this earlier, so we start from the “best” and then understand even more the difference that a road makes…… anyway, here is a graph, done in 10 minutes (!) drive on what I consider the best road we have here. It is on the stock OE Beetle, at 40 PSI super pressure too. Now, compare that to the same car, same tire pressure, but different road (yeah, believe it or not, that one is called “road” too!) and only 60 seconds run. It tells quiet a lot, I think….


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## ruking (Apr 4, 2003)

*Re: Force vs. Absolute Velocity (pyce)*

Good Stuff Pyce!! 
Essentially this kind of stuff was what I was used to looking at when I did both bomber and fighter analysis and missile work. (25-30 years ago!!!) 
It is great that one can buy the software and of course hardware packages AND DIY !!! This kind of analysis is almost essential in modern day racing!!! Its a great thing to bring to a forum such as this! 
While I think folks will know that the second graph is essentially a blow up of a 1 min segment the first graphic (of 10 min) , I think the two together might show why the same set up specifically your 1/4 turn Konis might generate two entirely different opinions if the opinion generator were not mind full of his methodology for generating ones opinions.


_Modified by ruking at 8:10 PM 11-4-2004_


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## f1forkvr6 (Jun 10, 2002)

*Re: Force vs. Absolute Velocity (ruking)*


_Quote, originally posted by *ruking* »_While I think folks will know that the second graph is essentially a blow up of a 1 min segment the first graphic (of 10 min) , 
Two different graphs - two different roads. Notice the top graph never crosses 5 m/s/s, while the bottom one does.
I beleive there is one missing variable -- vehicle speed. My intuition tells me that if you hit the same bump at 5 mph and then hit it again at 25 mph the results will be different.


_Modified by f1forkvr6 at 3:57 PM 11-4-2004_


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## ruking (Apr 4, 2003)

*Re: Force vs. Absolute Velocity (f1forkvr6)*

Perhaps I can say it better, if there is any "tie in" or relationship with the two graphs if you could scale the 2nd graph the same size as the first you will find that the road difference makes a lot of difference to the same set up, the same set up being the constant??? the different road being the variable? . Because if it were not you could really draw no relationship conclusion to these two different graphs.
"I beleive (sic) there is one missing variable -- vehicle speed. My intuition tells me that if you hit the same bump at 5 mph and then hit it again at 25 mph the results will be different."
I am not sure of the distinction you are making? The three graphs at different speeds (6/7/10 mph) and the results are measurably different?? Or is it you wanted to see a bump hit at precisely 5/25 mph? (with the results graphed)? 



_Modified by ruking at 9:33 PM 11-4-2004_


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## alexb75 (Dec 29, 2002)

*Re: TC vs. TC .... (.je)*


_Quote, originally posted by *.je* »_
I'm late to this party and prone to asking stupid questions. Alex, does this suggest that compressing a pressurized shock will give you higher compression damping, and a harsher ride? Ive heard both answers (yes and no).

I am not too sure. I think what happens on Bilstein case is that the valve move up on each impact and the shock gets harder and harder... so on a prolonged stretch of road it gets harder... but if you hit one bump at a time the valve comes back to its position. 
This has been my experience and the experience of some people who test the Bilstein high-pressure shocks for M3. I am still waiting for someone to explain the auto-valving phenomenon (or marketing hype) of Bilstein sport/hd.


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## pyce (Nov 7, 2001)

*why the last grpahs....*

I guess I did not explain it well again and it made no sense...... the car is the same, same tires, same pressure just the road changes (speed is same too!). The only reason I wanted to show this is for people to realize what a smooth road would do to the graph. Basically, I am trying to say that this is probably the main reason why I complain about ride quality. Because most of the roads where I drive will give me the lower graph and now you all can see *by how much* a good road makes difference. My point is, people love the TCs, but it is perhaps because they have roads like the top graphs shows, so they stiffen little bit the car, but because the roads are good, the have still better ride quality than my stock NB on bad roads. At the same time I wanted to show how sensitive the accelerometer is. You all have seen "busy" graphs so far and perhaps someone may have thought "Well, there is not much difference among them" and therefore may neglect the difference the graphs are showing, but this is because none of you had the idea of what a “comfortable” graph looks like. Now you can see what a comfy road “looks like” through an accelerometer’s graph and it becomes easier to evaluate how much discomfort there is due to just the road quality (graphs wise), everything being the same. The reason it was 10 minutes, because the graphs was so NOT-busy that if I had shown a 60 sec stretch would have looked almost like there is no graph, as the vertical disturbances were very rare (time wise) and very small, most of them well within 1 m/sec. Hope it is clearer now


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## pyce (Nov 7, 2001)

*True, Real OE replacement?*

Anyone of you fine people here, have a true experience with an aftermarket damper that is a real exact substitution for our OE dampers? Basically what are the options for a stock guy who wants ot replace his stock dampers with something "exactly the same" but not OE? Ok, let's give some margin here, I guess it will be hard ot find the exact same, so who makes a real plus/minus 5 % of what the OE damper is? I am really not in a mood to buy all existing on the market dampers and then to find out they are not any near as advertised, so if someone had experience with some unknown or not-popular damper that is "almost" OE but will be able to outlast and OE damper - please let me know. I would like to concentrate on finding a true aftermarket OE replacement, for those who wish to stay "stock" but do not want to replace dampers every 30K .... Thanks!


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## f1forkvr6 (Jun 10, 2002)

*Re: True, Real OE replacement? (pyce)*

Peter, the closest I've come is the Boge Turbogas. Close to OE -- compression didn't "feel" harsh, and was certainly softer than the Bilstein HD, but even these were advertised as a "performance" damper, 10% stiffer than OE for my A2. The Boge "Automatic" is billed as a true OE like damper, but I've had no experience with these. Both dampers come with a limited lifetime warranty (like the more sporting dampers from Bilstein & Koni).
The trick will be able to meet both criteria -- stock like ride qualities AND longer lasting than stock.


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## pyce (Nov 7, 2001)

*Re: True, Real OE replacement? (f1forkvr6)*


_Quote, originally posted by *f1forkvr6* »_ ....The trick will be able to meet both criteria -- stock like ride qualities AND longer lasting than stock.

That is precisely what I would like to go after! I am going to do some reading on the "Automatic".... as for the "Turbo Gas", as soon as I hear "10% stiffer than stock" and the TC experience comes to mind and I somehow no longer feel interested in exploring more


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## Ceilidh (Jan 7, 2004)

*Re: True, Real OE replacement? (pyce)*

Peter,
I had the Boge on my A2 (it was the model just below the Turbo Gas, but back then there wasn't anything called "Automatic" -- maybe it's been renamed?). The ride was quite comfortable, but the shock didn't last more than about 40k miles. I went through two sets (plus the OEM) by the time I sold that car...
When I first started looking for shocks for my GTI, what I really wanted was the Koni Red, and was disappointed to learn that Koni didn't make one for the Golf/Jetta IV chassis. If your buddy Phil (the shock guy) can revalve your Koni Yellows to a quasi-Red stiffness (perhaps only on the compression, as the rebound on full-soft might well be gentle enough), then that might do the trick for you.
(If you ever talk to a Koni rep, please ask why they never came out with a Red/Special for our cars -- it's a curious omission...)
- W


_Modified by Ceilidh at 11:50 PM 11-5-2004_


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## Ceilidh (Jan 7, 2004)

*Re: True, Real OE replacement? (pyce)*

Hello Peter,
Here's something a little curious: I just looked on Koni's international site, and there actually is a Koni Red for the Golf & Jetta IV (called the Bora in Europe, as you well know):
http://www.koni.com/_cars/_special/afram.html
They don't recommend it for "Sport" suspension-equipped cars, and it must be pretty soft if they spec it for the 1.4 litre editions. Anyway, not suggesting you go out and buy a set(!), but perhaps somebody there can give info on how much the damping level differs from the Yellows....
Hmmm....another possibility is that you might be able to buy the Red valving, and have Phil swap it into your Yellows. I don't know how feasible it is, but years ago when I was working on my MG, I found a Koni application for it (gosh, that would have been nice!), but nobody in the US carried it. When I called Koni about it, they put me in touch with a Koni dealer who was willing to install the appropriate valving into a shock body, and the price wasn't too bad (sorry, can't remember any particulars -- it was years ago). Anyway, just wanted to mention the possibility.
Have a good weekend!
- W


_Modified by Ceilidh at 12:06 AM 11-6-2004_


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## pyce (Nov 7, 2001)

*Re: True, Real OE replacement? (Ceilidh)*

Winston, we kind of went through this (Koni Red) in the long thread, but after "discovering" that they are not sold in NA we kind of discard the idea..... Glad your brought it back! I actually found a relatively cheap place that sells them in Italy and a set of those were ordered. Koni USA would not give me the "values" for the Red, so Phil will not be able to transform the Yellows into Reds. And anyway, I am not so interested in rebuilding, because this is not a cheap solution for everyone. The ideal scenario would be to find a real replacement, but as Chris said, to last longer, so people do not need to replace their OE dampers every year or so. Anyway, once these arrive, we will of course dyno them and will see where they are in comparison to the various OE we have and the Sport as well. They are internally adjustable as well, so perhaps could be set to match perfectly every trim and engine. As you noted, those are offered for the 1,4 – 1.6 – 1.8 and 1.9 engines, but not for the Sport Package, V5, V6 and 4 Motion, so they may really be the ticket for an alternative to OE ride quality, with possibility for slight adjustment to get those 5-10% if really needed…… We will see soon.
For those interested in the Koni Red (Special) for Golf and Bora, the part numbers are:
Front – 87-2571
Rear – 80-2761
Here is an old graph we used in another thread, that indicated where is (roughly) the Red positioned in comparison to the Yellow:


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## pyce (Nov 7, 2001)

*Word on Koni Red ....*

Got a word from Koni in Europe, and they said that the Red are valved in a way that full soft all around corresponds to the OE damper's settings! So, perhaps the 1/4 turn could be the nice place to start with, just to get the nice 5% (or around there) touch of sportiness. As you all may know, the Reds are not externally adjustable in the front, therefore we have ot try to make our mind first and do it right from the start. I guess the dyno may help big time, even if special adapters have to be made as to accommodate a front strut on the dyno. Then we can dyno the front OE and the front Koni Red on different settings and from the graphs try to see where to go with the initial setting. Later on this will help (the graphs) to guide people with their initial install. More on the Boge alter today....


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## MikekiM (Aug 21, 2001)

*Re: True, Real OE replacement? (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_Peter,

(If you ever talk to a Koni rep, please ask why they never came out with a Red/Special for our cars -- it's a curious omission...)
- W

_Modified by Ceilidh at 11:50 PM 11-5-2004_

KONI Red's are made for the MkIV. They just aren't imported here to the US through KONI NA. They're available, I've personally installed a couple sets. Vogtland includes them in their suspension kits.


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## pyce (Nov 7, 2001)

*Re: True, Real OE replacement? (MikekiM)*


_Quote, originally posted by *MikekiM* »_
Vogtland includes them in their suspension kits.


Do they sell them separately? You seem to mention that name very often, so I guess you have more info than anyone of us could get through a phone. Thanks.
edited - Forget it, I called them and the word is that there is agreement with KONI USA that those (the Reds) are sold only as a kit and not separately. So, basically one has to get their lowering springs together with the Reds for 550$ plus shipment and then enjoy the ride. The springs could be sold later thought, so the price drops to about 400-450$ which is still quiet a lot, considering that the fronts do lose the external adjustability. Perhaps revalving the Yellows is a better way to go as it will keep the front external adjustability....... But aren't Koni US such a wonderful crowd - not selling something and at the same time not allowing others to sell it neither!










_Modified by pyce at 11:19 AM 11-9-2004_


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## Ceilidh (Jan 7, 2004)

*Re: Word on Koni Red .... (pyce)*


_Quote, originally posted by *pyce* »_....the Reds are not externally adjustable in the front, therefore we have ot try to make our mind first and do it right from the start.....to see where to go with the initial setting.....

Hi Peter,
I've been thinking on this a bit, and there might be an empirical way to do it (in conjunction with the dyno tests). Koni appears to have done an extremely good job getting the "gain" on the shocks to be similar front to rear: in all my experimentation with the Yellows, wherever I've set the rear Konis, the fronts always come in to within 1/8 turn or so for maximum comfort.
Hence, since it's rear impact harshness that limits your damper stiffness, you could try installing just the rear Reds first and experiment to find the stiffest rear setting that has an acceptable impact ride. Then, the front setting will likely be within 1/8 turn of that...
Anyway, just a thought....


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## pyce (Nov 7, 2001)

*Re: Word on Koni Red .... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_ ...Hence, since it's rear impact harshness that limits your damper stiffness, you could try installing just the rear Reds first and experiment to find the stiffest rear setting that has an acceptable impact ride. Then, the front setting will likely be within 1/8 turn of that.....

Great! It makes sense. This is what I would do. Thanks again!







I have hard time to find Boge Automatic for A4. Few places offer then for up to MkIII and that is it. Tried to contact Boge-Sach directly, left them a message and hope they will call back soon....


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## pyce (Nov 7, 2001)

*Re: Word on Koni Red .... (pyce)*

Well, Boge has yet to release "Automatics" for A4 models. The website says "TBA" and distributor confirmed that too. So, those are out for now....
What about the Monroe "Sensa-Trac"? Anyone had experience with them? At least those could be found everywhere.... Did some reading and it talks about some "special" design that allows position sensitive dampening. Is that true or it is some sort of marketing call again? Here is a quote from the Net:

_Quote »_Monroe Sensa-Trac builds upon proven gas pressure shock absorber technology used in the Monroe Gas-Matic design and incorporates the innovative Position Sensitive Damping (PSD) feature which enable the shock absorber to adjust automatically to changing road conditions. 
The PSD design incorporates a unique precision tapered groove machined into the wall of the pressure tube. The groove has been designed and re-tuned for each vehicle. The groove functions as an additional oil bypass around the piston assembly as the piston travels through the grooved area thereby providing Sensa-Trac with an additional damping zone. This additional zone enables Monroe's engineers to design Sensa-Trac so it responds as a "double-action" shock absorber that automatically senses and reacts to changing conditions.


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## ewongkaizen (Apr 19, 2002)

*Re: Word on Koni Red .... (pyce)*

My understanding from the "off road" groups is that the "theory" of the Sensa Track is there - but IMHO the reality is not...
For the shock to work right - the seal along the piston needs to divert the fluid through the piston and through the "valves". If you cut slots int the walls - how long before the seals along the walls are "torn up" by the slots?
BTW - one COULD argue the same thing for the "holes" drilled for "bypass" tubes as well.
But also the problem is that the bypass tubes will route the oil PAST the valves - whereas the slots will NOT .
ALso- there is a recent issue of one of the off road mags (I can recall which - I get a ton of em) that has LOADS of pictures of the guts of the super trick bypass off road shocks... VERY interesting....


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## apr2009gti (Sep 25, 2003)

so for a guy that has some shine springs in a box and needs to order some shocks. No racing
.
Are the Konis sports still the best for comfort?
01 golf 2dr TDI


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## f1forkvr6 (Jun 10, 2002)

*Re: (ryker77)*

What kind of pavement conditions ...?



_Modified by f1forkvr6 at 9:22 PM 11-12-2004_


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## alexb75 (Dec 29, 2002)

*Re: (ryker77)*


_Quote, originally posted by *ryker77* »_so for a guy that has some shine springs in a box and needs to order some shocks. No racing
.
Are the Konis sports still the best for comfort?
01 golf 2dr TDI


For comfort your springs are too stiff... but if u wanted to get some shocks that are comfier... Koni is nicer riding than Bilstein at lower rebound setting.


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## 2beirish (Apr 28, 2004)

*Re: (alexb75)*

I'm very appreciative of the time and money spent to generate this data. Since I'm at the point where I'm ready to install struts/shocks, springs and larger sway bars on my 03 Jetta Wagon this info is invaluable.







I've tended to use Bilstein HDs or sports on all my cars and trucks, because the ride quality, rebound and damping appeared consistent from day one. I ran Koni reds on an old Fiesta years ago, but they leaked, and Koni Yellows on my race-modded Mustang Cobra were too difficult to tune front & rear to get the neutral handling for my non-analytical mind. So I've tended to go Bilsteins because the ride and handling improvements are apparent and I don't have to figure out adjustment settings front & back. BUT these graphs and discussion give me pause, and make me wonder whether I should be considering Konis again. I eagerly await your Bilstein HD and Sport analysis. I'm also wondering whether you wish some help paying for all this invaluable and thoughtful work: just ordering the dampers gets expensive. I'd certainly be willing to PayPal a bit of moolah just to keep the shock dyno pumping up & down. Thanks. Walter


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## virtual_dub (Sep 8, 2003)

*Re: (2beirish)*

my $0.02
Just to make sure I understand the goal of this testing. I believe you're trying to compare shocks to find one that provides the optimum trade-off of comfort and performance.
What I'm really interested in is the accelerometer readings because they show the actual movement of the car over the same road conditions. All of the research on suspensions for consumer vehicles has duscussed the frequency of the suspension oscilations. This has been mentioned here and there, but I haven't seen any tests. A couple times in this thread people refer to the "rate of change" of the shock piston and how at different rates of change the shock behaves differently. This is more accurately related to the frequency of the shock-spring system. Dynamically the vertical position (the one were're concerned about for comfort) can be modeled as a damped harmonic oscillator with some input from the road, although it's probably a little more complex.
Ideally we want the shock-spring combination to resist change at low frequencies, so it follows the road and prevents roll. At high frequencies (expansion joints and pot holes) we want to absorb as much of the movement.
I think we should analyze the accelerometer graphs by looking at how the car behaves at different frequency oscillations. We could do this by looking at the power spectrum of the vertical car movement. For comfort you want to reduce the power of the high frequency oscillations and the very low frequency osciallations (think motion sickness). There's some frequency which we aren't as disturbed by, I don't recall exactly but I think it's around 1Hz. So by looking at the power of the frquencies that the car is moving at we can see how a given shock may "filter" out the higher frequencies better than some other shock.
I appologize if my terminollogy isn't very precise/correct, I'm used to dealing with electrical signals and not mechical oscillation.


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## alexb75 (Dec 29, 2002)

*Re: (virtual_dub)*

That's a great idea. So, what you're saying is to have an accelometer test of "for instance" a slalom... right? Like going through some cones at a set speed with different shocks...
Did I understand you correctly?


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## virtual_dub (Sep 8, 2003)

*Re: (alexb75)*


_Quote, originally posted by *alexb75* »_That's a great idea. So, what you're saying is to have an accelometer test of "for instance" a slalom... right? Like going through some cones at a set speed with different shocks...
Did I understand you correctly?

Not exactly. I actually mean that we can look at Peter's accelerometer graphs not over time, but in frequency. If we look at what frequencies are present in the motion and their relative powers this will give us an idea if one shock is better at reducing high speed oscillations/bumps than another. I'll try to work up an example with some graphs and post it later.


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## ylwGTI (Jan 18, 2002)

*Re: (virtual_dub)*

Pyce, did you consider KYB AGX adjustable shocks?
They are both rebound and compression adjustable. 
You can get a set for around $350
I think at low settings they would be like stock.
We just installed it on my buddie's Jetta along with Eibach Pro Kit.
The KYB's seem to be working good with the setup and the adjustments make a difference. He said on 50% it feels just like stock suspension.


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## pyce (Nov 7, 2001)

*Re:*

*2beirish* – Thanks for the generous offer! Very nice of you to offer some help, I deeply appreciate it! But I rather have folks send me their dampers, so I do not need to buy them. That would be much greater help. And that is also the reason we do not have HD and Sport yet, as it is not easy to coordinate (even if donor is located) because most of the time the guy has to come directly to the dyno shop and we jack-up the car and take the damper and then put it back all in the evening so he can go home, and of course not many people are very keen in doing that. For the rest I am fine, the dyno is not super expansive and had been giving me a discount lately, so I will survive. I have been smoker for 15 years and two years ago managed to miraculously quit smoking, so I decided to pour those money (that were going to be wasted anyway in cigarettes) into mods and experiments and tires and all sorts of stuff that is a waste too, but at least there are some lessons to learn from this type of waste….. So, here we are….. I will try my best to organize the HD & Sport dyno as it is very important for the whole community. There are so many talks go around (from time to time) how they compare and how one is this and the other one is that, and usually it is all from what people heard or read, but not from real experience with both products, so it is important we put this issue to rest.
*ylwGTI* – The KYB AXG were on the list! I found that the Tirerack sells them, so I gave Eric a call and spoke to him. He said (he tried them) that the KYB are not more comfortable (on any setting) than the Koni Yellow and that is precisely why I simply skipped them. Now, you are saying they are as comfortable as stock and I am confused. Do not want to doubt you, but Eric has always treated me well and in the past also have talked me out of buying stuff from him, which I respect very much. A vendor that talks you out from something you want to buy and he sells is (to me at least) some one who could be trusted. Again, I do not want to doubt you as I do not know you, but perhaps where you guys tested the car with KYB – the roads are good and therefore not big difference was felt? Could that be? If those are really as you said – that they have a setting that provides stock or very close to stock comfort – then that could definitely be “da damper” because it is not so expansive and a the same time offers external adjustability, which is simply all we need – to have comfort on a bad day and stiffen it up if/when needed. Let me see if Eric would sell me just a set of rears, or perhaps just let me have them to dyno them….
As for what “virtual-dub” is saying….. we happen to be neighbors, as he moved recently to CA, so we met last night and spent some time in his ride and recorded some data on the “testing track” from his setup. I will be posting it later. He has an interesting idea and we will we waiting to see what he comes out with later on, when the data is elaborated.


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## edisonr (Oct 24, 2003)

*Re: (ylwGTI)*

Do you have the p/n for the TC sports and standard? I'm looking for a set of shocks and struts to go my Neuspeed Sport springs and I would like to see the results for the *KYB AGX* too.
Thanks
PS: excellent post http://****************.com/smile/emthup.gif this is the reason why I hang around in vortex.


_Modified by edisonr at 12:45 PM 11-16-2004_


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## pyce (Nov 7, 2001)

*Re: (edisonr)*

Here are the part numbers for the rears only. Do not have the fronts on the Standards, have the Sport fronts, but not handy, so you have to either wait for those or someone else has to give them to you.... 









Here is a zoom-in on the upper part of the two dampers. It shows pretty clear how the "Standard" have a metal top cup (which makes them taller by little bit) and the "Sports" have a plastic cup like the OE dampers, even if it looks beefier....... So, beside the compression and rebound characteristics, this is the only other difference that strikes from outside. Again I do not really understand how is this mean to be "for lowering springs" as many are saying? All I can "notice" is that when used with lowering springs, the rear bumpstops are constantly on those cups but Bilstein made them from plastic. Shouldn't the "Sport" be in metal down there? That is really pretty much all I can see with a naked eye. I still can not understand the sentence "they work better with lowered springs".... How do they (the dampers per se) work better with lowered spring?








edited: To add the front part numbers:
Bilstein TC *Standard Front - VNE-4574-BE*
Bilstein TC *Sport Front - VNE-4575-BE*


_Modified by pyce at 9:35 AM 11-16-2004_


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## edisonr (Oct 24, 2003)

*Re: (pyce)*

Thanks pyce for the p/n. I would like also to see the results for the *KYB AGX* set. 
Here is a picture I found of Sport TC with the metal top (this picture belongs to a fellow vortex memeber who were selling them, I hope he doesn't mind):


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## pyce (Nov 7, 2001)

*Re: (edisonr)*

From the picture is clear that the part number is for the "TC Sport" but the dampers have then metal top cup, which I thought is coming only on the "Standard"...... so, perhaps Bilstein now puts the metal cup on both Sport and Standard, which makes half of my last post useless...... The other half is still valid thought - Why are the Sports better for lowered springs?


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## blackflygti (Sep 19, 2001)

*Re: (pyce)*


_Quote, originally posted by *pyce* »_Why are the Sports better for lowered springs?

Are the TC Sports shorter than the Standard? I've noticed that my Bilstein Sports (Yellows) are 1" shorter than my OEM shocks.


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## pyce (Nov 7, 2001)

*Re: (blackflygti)*


_Quote, originally posted by *blackflygti* »_
Are the TC Sports shorter than the Standard? I've noticed that my Bilstein Sports (Yellows) are 1" shorter than my OEM shocks.

You can look at the second picture I posted above. That is the difference in length. Few millimeters at max and if they started selling the Sport with the metal cup (as shown from the guy above) there will be no difference at all.....
On another note - just managed to find rear only KYB AGX. They will be here in two days and we will see what they do on the car and on the dyno. It is the last damper I am buying....


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## blackflygti (Sep 19, 2001)

*Re: (pyce)*


_Quote, originally posted by *pyce* »_You can look at the second picture I posted above. That is the difference in length. Few millimeters at max and if they started selling the Sport with the metal cup (as shown from the guy above) there will be no difference at all.....

That's only a shot of the where the piston shaft enters the shock body. What about the length of the piston shaft itself? The piston shaft on Bilstein Sport Yellows are 1" shorter than OEM. I'm guessing that's not the case with the TC or you would've noticed right away.


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## edisonr (Oct 24, 2003)

*Re: (pyce)*


_Quote, originally posted by *pyce* »_......as shown from the guy above....

The guy above is Edison


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## virtual_dub (Sep 8, 2003)

*Re: (edisonr)*

Not that I have xray vision or anything, but I'm guessing this is the difference between sport and standard.








Notice that the shock bodies are the same size, but that the compression travel remains the same (if you cut the bumpstops, and only for a particular amount of lowering). 


_Modified by virtual_dub at 2:03 PM 11-16-2004_


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## pyce (Nov 7, 2001)

*Re: (virtual_dub)*

Right on, Scott! Let's ignore the shaft for a moment.... If the bodies are the same means that the bump stop would sit on top of the damper at the same time, no matter which damper is used. The length of the shaft does limit the extension, so your real suspension will lift the rear wheel earlier from the ground (if the car is air born) and there are few things to say about that, but let's concentrate on the damper's bodies for now - Same body length means same ultimate suspension travel in compression (if everything else remains the same!) so I still have problem understanding how the TC Sport works "better" with lowering springs?


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## virtual_dub (Sep 8, 2003)

*Re: (pyce)*

You only retain the same compression travel if the shaft is shorter. Basically lowering will push the end of the shaft closer to the bottom strut mount, thus if the shaft is not shorter than compression travel will be limited.

_Quote, originally posted by *pyce* »_If the bodies are the same means that the bump stop would sit on top of the damper at the same time, no matter which damper is used.

I don't know that this is true. If we again think of a lowered suspension just like compressing the stock suspension an inch or so, than the bumpstop will sit one inch closer to the strut body (that is if the bodies are the same).
Someone pointed out that the Bilsten or Koni bodies are actually shorter. This will give back some of the travel between the top of the strut body and the bumpstop, but it takes away some of the extension.
I don't believe the car would go into full droop unless airborn for some period. I think it would be much more common for the wheel to loose contact with the road due to the rebound damping of the strut not allowing the wheel to follow the road over bumps.
Overall, the shaft must be shortened to retain compression with repect to the bottom of the strut body, and the body must be shortened to retain compression with respect to the bumpstop (or we can shorten the bumpstop). The later has the adverse effect of limiting extension.


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## pyce (Nov 7, 2001)

*Re: (virtual_dub)*

Wait a second here...... I was presuming that you all know that the rear dampers travel about 9 inches total. When mounted on the car and the car is sitting still, the shaft is compressed at about half of the stroke. Operation range, when driving around is at about 4,0-4,5 to 5,5-6,0 inches. In the way the rear is designed, the shaft will NEVER go to the end of it's stoke in compression! Even if you completely eliminate the buffers, and the metal part bottoms out, still there will be space left...... I do understand your logic and it makes sense, but this IF the damper were designed to completely run out of travel when mounted on your rear, which is not the case.


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## virtual_dub (Sep 8, 2003)

*Re: (pyce)*

I understand, that was one more assumption I didn't list. I guess those engineers did something right







. So if you remove the bumpstops you would hit the strut top with the top of the shock body before bottoming out the shaft inside the body. This makes sense since when the struts are out of the car you can compress the shaft pretty much all the way into the body.
So the limiting factor is the distance between the bumpstop and the top of the stut body (so my picture is wrong).
I understand your confusion now, what is the difference between the standard and sport Bilstein TCs given that the strut bodies are the same size?


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## pyce (Nov 7, 2001)

*KYB AGX ....*

The KYB AGX is here. For those who have not seen one, here is a pix from the parking lot. Made in Japan, externally adjustable, crazy color but with "beefy" knob to adjust compression and rebound at the same time. The interesting part is - they come with they own bump stops and dust covers! The gas pressure is very minimal, very easy to maintain them compressed with just few fingers. The knob goes in a loop.... I mean you can go to 8 position and then jump to 1 without a need to go back through the rest of the positions..... 









Another interesting part are the instructions. It clearly says to NOT use these dampers with lowering more than 1 to 1.5" and if that happens - the warranty would be voided! It says that their engineers will examine the shaft (if warranty claims are submitted) and will know exactly how low the car was, and based on that they will accept or decline the case.








Anyway, the important part is that this damper goes on the dyno this afternoon. At least those are the plans...... and later in the day may eventually end up in the car (it depends a lot on the dyno results). More later...


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## ruking (Apr 4, 2003)

*Re: (pyce)*

Sort of hand in glove going along with what you are saying is when you "lower" your car (with lowering springs)you are in fact truncating and or shortening your spring's suspension "travel" by that lowering amount say .5- 3in or whatever. Part of why springs are "progressive " is to compensate for this shortening. Part of the price is a harder, bouncier ride.


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## phatvw (Aug 29, 2001)

*Re: KYB AGX .... (pyce)*


_Quote, originally posted by *pyce* »_
Another interesting part are the instructions. It clearly says to NOT use these dampers with lowering more than 1 to 1.5" and if that happens - the warranty would be voided! It says that their engineers will examine the shaft (if warranty claims are submitted) and will know exactly how low the car was, and based on that they will accept or decline the case.










What if you drive around with 500 pounds of bricks in your trunk? Or 10x 15" subwoofers. Would they warranty it then?


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## pyce (Nov 7, 2001)

*Re: KYB AGX .... (phatvw)*


_Quote, originally posted by *phatvw* »_
What if you drive around with 500 pounds of bricks in your trunk? Or 10x 15" subwoofers. Would they warranty it then? 










We can eventually test that one too


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## edisonr (Oct 24, 2003)

*Re: KYB AGX .... (pyce)*


_Quote, originally posted by *pyce* »_Anyway, the important part is that this damper goes on the dyno this afternoon. At least those are the plans...... and later in the day may eventually end up in the car (it depends a lot on the dyno results). More later...

I'm so waiting for the results.


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## pyce (Nov 7, 2001)

*KYB AGX Dyno Results ........ Maybe the Japanese really nailed it?*

Just got back from the dyno and here we have some results from the KYB AGX….. At least on “paper” it is a very interesting damper and I would say that so far showed the smoothest curves ever, even better than the OE dampers we have seen so far! Here it is for you all to admire the Force vs. Displacement of the KYB AGX set at Full Soft (#1 on the dial) at the usual speeds from 2.00 to 30.00 in/sec….









Note how the absolute values are not very far from the OE values! Below here we have another graph that shows the KYB AGX (still at full soft) in comparison to the OEM Jetta TDI damper at our usual 18.00 in/sec speed. Note the shape of the compression curves (top left corner) are almost identical, but with slightly stronger values. When it comes to the Rebound curves (lower part of the graph), we can see how the KYB AGX provides more rebound (as absolute value) but it has also smoother curve all the way. The OEM damper gets the “knee” we have been talking about earlier…








Later on I will post a comparison between “full soft” and “full stiff”, so you would see what and how changes when we turn the knob……. The important part for the moment is that we are going to make a significant jump in understanding few things with the today’s product and data and here is why:
It is the first time we find stronger (in values) damper than OEM, but that also has even better than OEM “smooth curves”, so by testing this damper on the car, we will finally have a real-life confirmation (or not!) about whether the “knee” is causing the discomfort or whether is the absolute values! It is useless to say that these dampers go on the car in few hours, because on paper they look too good to be true. So, in few hours we could basically (with the accelerometer) understand whether this dyno could be trusted, because so far I always tried the dampers first and then we dynoed them. This is the first time we first dyno, and from the accumulated amount of knowledge (looking at the charts) we are now trying to “predict” what is the ride going to be – so, if what we have learnt so far is correct – these dampers should result as the real “5 to 10%” improvement over stock, maintaining the characteristics of the stock unit but just amplifying them. If the results from the real-life test are very different – then we have to go ahead and re-think all the stuff that had been said and done this far……More later.


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## TyrolSport (Mar 4, 1999)

*Re: KYB AGX Dyno Results ........ Maybe the Japanese really nailed it? (pyce)*

Peter and Ceildh, thanks again for excellent work






















I've been extremely busy with the shop here, but would love to help if I possibly can. I know your goals are more oriented towards street suspension setups, but I can do some track testing if would like to prove/disprove any hypotheses or conclusions.


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## ruking (Apr 4, 2003)

*Re: KYB AGX Dyno Results ........ Maybe the Japanese really nailed it? (pyce)*

Pyce,
Thanks for testing the KYB AGX ! As indicated in a prior post, it did come across my research radar. (along with Tokico Illumina) 
(because of planning for a 2004 Honda Civic 4 door automatic)







. 
It seemed to me the engineering problems were fairly similar, i.e., front wheel drive, front engine, ball park hp/torque etc etc
I started putting two and two together and it seemed like the KYB AGX could be applicable to the VW side.








I am also looking forward to your SOTP's impressions.


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## pyce (Nov 7, 2001)

*KYB AGX First Drive...*

First impressions…. These dampers are with the biggest shaft so far. The stock unit and the Bilsteins were 11 mm. The Koni Yellow is12 mm and this one is 13 mm diameter. Not that it will change the price of the rice in China, but have to cut new spacers (duh). The dampers’ body is also the largest I have seen so far. Do not have caliper here, only micrometer, so could not take numbers, but it is visibly beefier. Basically, if we were just to look at all those dampers next to each other, I would be inclined to say that the KYB AGX is the “Heavy Duty”, even if in reality it is not…. The next thing to note is that the body is the exact same length (maybe one millimeter difference at most) as the OEM damper. It comes with it’s own bump-stops, which are about 1” shorter than the already shorter “C” bump-stops. So, this is indeed the first damper I got that at least is more “lowering-friendly” as they provided shorter bump-stop. The thing is, thought, that buffer is hard-rock stiff and it is good that it is short – you really do not want to ride on it – it is like carbon dressed in softer material. It took some real pulling to even separate it from the dust cover. Now, another reason they supplied the bump-stop could be that the stock bump-stop would not go on the KYB AGX’s shaft (because of the diameter difference pointed above). Another thing to note is that the KYB buffers are somehow smaller in the outer top diameter and they do not “Stick” in the holder, so I guess some sort of glue or whatever needs to be applied later. I do not care about that part at the moment, but it is worth pointing it out as someone may wonder why his buffers “dropped” down on the first drive. They also come with their own nut for the top. It is in a small plastic bag together with some “AGX” stickers, so you may not notice it and throw the bag, but you better remember where you wasted it as you will need that nut, it is different than the stock unit….. The rest is ordinary damper replacement.
As for road behavior, it is too early to say as I only drove little bit last night and this morning to work, so it is not enough to talk. (I got very nicely fooled in the past from “short” test drives and now lesson learnt – so no definite talks before at least 500 miles go on them). Few things I would dare to say thought, these dampers are stiffer than OEM even on their softest setting. They are also (as a first impression) softer than the Koni Yellow when set on full soft and significantly softer than the Bilsiten TC we tried. I do not know whether these will remain in my car for good, as more driving is needed to decide, but from what it looks so far – these may be a very good “compromise” for many of you, who do feel the “Sport” dampers like Bilstein Monotubes and Koni Yellows are too stiff and the stock is too soft. I have no idea how these will work with strong springs. The rebound curves do not look bad and there are seven more positions for increased stiffness (rebound and compression at the same time) . The nice part is the external adjustability. Those getting tired of taking out their Konis every time will deeply appreciate this device







If these can get to where the Konis get at about 60-80% stiff, then perhaps could be a great (and cheaper) alternative with the external adjustability as a great plus. The things that remain to be tested is the long term functionality, where we know Koni and especially Bilstein are leaders. On the KYB web site I read that they are the biggest OEM manufacturer in the world. Do not know how true is that, but if it is indeed true – then perhaps they do have the expertise and experience to build reliable products. We will find out, I guess. 
We can also do something interesting with this one….. I will drive on them for about 500 to 1.000 miles and will take them out and re-dyno, so we can perhaps learn little bit more about what does a “break-in” do graphs wise, is there any changes we can detect and how much those changes are, where precisely, etc….
Another good news here is that someone is shipping almost a brand new HD from the East Coast to me as we speak, so hopefully next week we will have our first Bilstein HD dyno. The gentleman does not mind me mounting the damper on the car and doing some runs with the accelerometer, so we will have some more data to look at. He is not a member here yet, so there is no screen name to be mentioned, but I thank you very much for the generous offer!


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## Cadenza_7o (Jan 23, 2001)

*Re: KYB AGX First Drive... (pyce)*

Interesting... I like the adjustment dial! http://****************.com/smile/emthup.gif


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## pyce (Nov 7, 2001)

*KYB AGX More Impressions....*

More first impressions …… Took it for a drive around lunch time, but this time the knob went to #8 (full stiff). Very interesting was to discover that the difference in comfort from full soft to full stiff is very, very minimal! I know sounds nuts, but perhaps some other KYB owners can confirm. I would not use that setting for long highway driving, but can definitely live with it for short trips, etc. It felt more or less like you upped the tire pressure by few pounds. The even more interesting part is that doing slalom makes a lot more difference. I mean, if we can use some numbers to just make a point (purely talking point, do not get them as real evaluation!) I would dare to say that on full soft the comfort feels like 8 and on full stiff feels like 6. (let’s say 10 is stock) Slalom wise thought, the weight transfer feels much more affected by the settings, so the full soft feels again like 8 but the full stiff feels like 4 – 5 (here 10 is stock, but the lower the better). Basically, it felt (but again, more testing will tell the real story, this is just initial feels) like they have a got some sort of “Secret Valving” with which you can gain some transition stiffness (in slalom, changing lanes, etc) without losing that much of a comfort. The Koni Yellows were very linear in the adjusting – you go soft and it rolls more and it is more comfortable. Then you go stiff and it rolls less but also rides very hard. These here seem to respond in not-so-linear way, so you can gain some “performance” without losing much comfort….. 
A very important note here must be made thought. They (the KYB AGX) on their full stiff are not any near the Koni Yellow at full stiff! So, those of you who are “track oriented” may simply skip this damper, even if it is really nice that knob to have. Man, what a pleasure to stretch your hand behind and “click” – done! The only thing missing from the KYB package is the “specifically designed” KYB carpet so you can adjust in clean elegance, LOL








Anyway, one thing is sure – I can stand these dampers so far, which means they will remain in the car for the whole weekend at least. We have some long driving to do for the next three days, so it will be perfect to see what else can we find while sitting in the car for more than just half an hour. The big punishing long concrete is yet to come, so I want to remain skeptical till then. Also, do not forget two other important things. My car is on 15” tires at the moment, huge contributor to comfort and I have OEM dampers (and springs) on the front too – another huge contributor to comfort! So, if someone here goes out and puts these on his 18” wheels and stiff, lowering springs, and have bad results – do not blame me for misleading you – I have no idea how these will perform with more than stock springs and tires. More later…


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## edisonr (Oct 24, 2003)

*Re: KYB AGX More Impressions.... (pyce)*


_Quote, originally posted by *pyce* »_So, if someone here goes out and puts these on his 18” wheels and stiff, lowering springs, and have bad results – do not blame me for misleading you – I have no idea how these will perform with more than stock springs and tires. More later…


That sounds like my case, 18" wheels and Neuspeed Sport springs (not in the car yet) waiting for new shocks and struts. I think KYB is they way to go.
This topic is really getting my excited. What a an excellent work pyce http://****************.com/smile/emthup.gif 


_Modified by edisonr at 2:28 AM 11-20-2004_


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## pyce (Nov 7, 2001)

*KYB AGX - Full Soft vs. Full Stiff ...*

Here is the dyno chart at max speed (30 in/sec) that shows the KYB AGX on full soft vs. full stiff. It shows very little difference (if compared to Koni Yellow) and perhaps would be interesting to know what is hiding behind this “philosophy”. I mean, once you have figured out a soft setting that gives comfort and such, then why not make at least the last two clicks to be really distinctive high? Anyway, if compared to the Koni’s rebound, the KYB AGX would be positioned somewhere in between 40% stiffer than Koni and 60% stiffer than Koni. The compression, thought, (of the KYB) is also noticeably smaller, with a slightly smoother curve too, so perhaps that is (the curve, the lack of “knees”) really one of the reason why we have better comfort with KYB than with Koni on related settings….


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## pyce (Nov 7, 2001)

*KYB AGX and the OEM ....*

A very wild thought here …. What if actually these are meant to be just a tad “sportier” dampers and the whole adjustability is nothing else but just to “tailor” them to the variety of stock springs that we have across the whole A4 platform? We are slowly discovering in another thread how VW offers more than 55 front springs just for the A4 platform (perhaps there are more, I do not know!) and with all different bodies and engines – the need of slight adjustability comes handy. I may be totally wrong but look at the above graph (KYB stiffest vs softest) and look at the graph below (re-posted from earlier page) where we see the Jetta TDI damper vs. the Golf TDI damper…..








Rings a bell?...... So, perhaps it is wrong to even trying to compare them to the Koni Yellow, because the Konis are at very different performing levels from softest to stiffest, while the KYB are just have just “narrow range” for the “tailoring” mentioned above… Could it be?


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## Ceilidh (Jan 7, 2004)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (pyce)*

Hi Peter,
Sorry to have been away for so long(!); I'll try to write some more this weekend, but here are a few initial comments:

_Quote, originally posted by *pyce* »_Here is the dyno chart at max speed (30 in/sec) that shows the KYB AGX on full soft vs. full stiff. It shows very little difference (if compared to Koni Yellow) and perhaps would be interesting to know what is hiding behind this “philosophy”.


1) Please forgive me for being a wee bit cynical, but my first reaction to what is "hiding behind this 'philosophy'" is that it's a fairly classic example of Japanese marketing/engineering (and yes, I know I'm painting stereotypes with a very broad, perhaps unfair brush, but there are certain national tendencies you see repeated over and over across a host of different industries, and this one is fairly typical). There's something faintly absurd about a shock that makes a big show of having an enormous (permanently-mounted?) hand-adjustable knob.....that turns out to make very little difference in the internal damping level. That's the downside of the national (engineering/marketing) stereotype: we have a product here that noisily proclaims features we think we want (easy & significant adjustability), but which in reality is partly a sham. (Contrast that with the enormous (almost 2:1) adjustment range of the Koni, which is so successfully downplayed (especially in the internally-adjusted rear shocks) that every month we see posts from people who think the rears can't be adjusted at all)... So part of what we're seeing here is marketing manipulation: it's quite obvious to all manufacturers that enthusiast consumers want easy on-the-car damping adjustment capabilities, and KYB is "giving" us that capability ("....just like the Konis only much more easily adjusted!!!!....") without really giving it at all.
2) Of course, there's an upside too: if we stay with the Japanese marketing/engineering stereotype, we also expect there to be some fairly subtle and well-thought out engineering that meets our *real* needs without our particularly realizing it; and there appears to be some of that here as well:
There appears to be about 15-17% adjustability in the compression and perhaps 7-8% in the rebound -- not a whole lot, but let's look at this range in a little more detail; when we do, we see there's actually some real benefit to what KYB is doing, and in effect they're sort of helping us despite ourselves:
The crux of the matter is what determines damping level: in engineering terms, the relevant concepts are "damping ratios" and "critical damping" (any detailed suspension engineering text will cover them; if you want to look in Milliken, they're on pages 786-794), but for our purposes here we can simplify them by saying that to maintain a given level of comfort and performance, we have to change the damping in accordance with the square root of the masses and spring rates being damped. That is, if we quadrupal the masses or the spring rates, we need to double (not quadrupal) the shock damping.
(Or it put it in completely non-mathematical terms, a small change in damping can accommodate a big change in spring rate, or vehicle & wheel weight.)
So let's look first at the rebound: rebound damping (to a rough approximation) controls body motion, and is tied to the mass of the sprung weight and the strength of the primary springs and antiroll bars. The 7-8% adjustment range of the KYB's can accommodate a roughly 16% variation in spring rate and/or body weight -- and that's roughly what we see in the Golf/Jetta. According to the VW website, the lightest (in the rear) A4 car is the Golf 2.0 Auto at 1102 lbs, and the heaviest is the Jetta GLI at 1259 lbs. That's a 14% difference, and if it's really true that the rear springs on these cars are all pretty much the same strength, then the KYB can accommodate it.
As for the compression (where the ~16% damping variation can control a ~35% variation in mass or spring rate): again to a rough approximation, the compressional damping controls the unsprung weight, and here the biggest variation comes from the difference between a 18" 225/40-18 GLI tire vs. a 195/65-15 Golf 2.0 tire. The wheel experts can tell us how much these tire/wheel combos can differ in weight, but assuming that the rear unsprung weight is roughly 15% of the total rear weight (i.e., about 80 lbs/ wheel), then the 35% variance that the KYB's can handle comes out to ~28 lbs -- which is in the very rough ballpark for the weight variations between different wheel/tire combinations.
3) Bottom line, your suggestion (in a later post) is plausible, that maybe the adjustability of the KYB is primarily there to adjust the shock to different models of the Golf/Jetta IV line....

_Quote »_
Anyway, if compared to the Koni’s rebound, the KYB AGX would be positioned somewhere in between 40% stiffer than Koni and 60% stiffer than Koni. The compression, thought, (of the KYB) is also noticeably smaller, with a slightly smoother curve too, so perhaps that is (the curve, the lack of “knees”) really one of the reason why we have better comfort with KYB than with Koni on related settings….


4) Peter, I'm not sure if I'm interpreting your graphs or the above comment correctly, but it seems to me that the KYB's are significantly softer than the Konis in compression, but firmer than the full-soft Konis in rebound (though significantly softer than the full-stiff Koni rebound setting). In this light, I would interpret the better comfort of the KYB (when compared to the full-soft Koni) as at least in part (and I kind of think primarily) due to the difference in compression. The "knee" here certainly plays a role, but at least on my GTI there's certainly an over-abundance of compression, and that (on my car) appears to be the main cause of discomfort.
5) A completely separate issue, but one which I think your work shows very clearly -- and which I think is very important -- is just how little damping adjustment we really need to affect the handling and ride comfort in our cars.
a) To wit: before you started these experiments, the standard expectation was that if one installed Konis, then (at minimum) half-turn to full-turn adjustments were the way to go (even TireRack did it in their test of Koni Sports -- they compared OEM to Koni Full-Soft to Koni Full-Stiff, as if people were expected to make massive changes in shock settings).
b) But as the Koni experiments showed, 1/8-turn adjustments made a big difference once the shock is basically close to the optimal setting (which took a long time to figure out, as Koni gave very little guidance for shock setting). Near that setting, an 1/8 turn had significant effects on both ride and handling.
So how big is 1/8 turn? Since the Konis have roughly 2-turns rotation from full-soft to full stiff, and since there's a 100% increase in rebound going from full-soft to full-stiff, an 1/8 turn adjustment rougly increases the rebound by ~6% (it'd be interesting to see whether the adjustment is linear -- I know it felt like the initial adjustments did much more than the later ones, but that might just be because adjustments feel bigger when they're near the optimal setting....). Anyway, perhaps not by coincidence, the 1/8 Koni turn is roughly in the same ballpark as the full KYB adjustment range.
c) One thing I haven't mentioned to you yet is that I've actually gone over to 1/16-turn adjustments on my front Konis (not on the rears - it's just too much of a pain to adjust!). This minute adjustment (which might equate to half the entire adjustment range on the KYB) has a very noticeable effect on both ride and handling.
d) In any case, my current suspicion is that there's nothing magical about the KYB damping curve (in terms of your being able to adjust handling with less impact on ride) -- instead, the comfort of the KYB comes from their being set more or less at the correct level to start with, and from their being so limited in adjustment that it's impossible to screw them up the way that one can so easily screw up the Konis.
e) Anyway, kudos to KYB for getting the initial damping to so close to where we need to be (at least for stock springs).
6) As a final note: I have reservations about the KYB's longevity. Yes, they're an OEM manufacturer, but so is Sachs-Boge, and the OEM shocks don't last all that long. Even my Koni fronts have softened in the past 15k miles (which is why I dialed them up 1/16 of a turn) -- but while the Konis have a huge adjustment range that we can use in compensating for wear, the KYB's don't have very far to go before you've run out of adjustment range.
On a more personal note, you know that in a former life I was an engineering project manager, and as such I might have become a little too cynical about how marketing/engineering interactions play out (i.e., feel free to discount the following), but there's something that just doesn't smell right -- engineering-wise -- about the KYBs. In a technology-driven engineering team, there's a pervasive pull for engineering elegance, and one of the thing that that pull translates into is a desire to do more with less. And from what you've described about the KYB's, that elegance appears to be absent. In addition to the enormous adjustor wheel that changes damping by only 15% (and the garish packaging promising "Strip, Street, Track, High-Speed Touring, Cruising" (when the shocks are clearly too soft for Track use)), there's also the matter of the oversize shaft and shock body. Nobody would use an oversize shaft if there's no need -- it's extra weight, and it takes up space that one would ideally like to use for hydraulic fluid -- and Koni & Bilstein have shown that there's no need. So why is the shaft oversized? Are they using an inferior grade of steel? Or are they trying to trick people into thinking it's "heavy-duty"? Ditto for the shock body: packaging space is tight in many cars, and a large shock body will lead to clearance problems in certain cars with certain tires, so you never make it larger than you have to -- so why is it so large?
In any case, there's a lot about the KYB that smacks of marketing fluff. The adjustment wheel, the limited adjustment range, the promises on the box, the "heavy-duty" shaft and shock body (that add essentially nothing to the variable cost of the shock, but which make it look beefier) -- all these things make me uneasy. It's the sort of thing a company does when it tries to sell a very ordinary product to unsuspecting people who perceive it to be something extraordinary.....
7) Regardless, I hope you get the Koni Reds soon, and it'll be interesting to see how they compare comfort-wise to the KYB's. It looks like they'll have a more "square" dyno curve, but their compression will likely be down near stock levels, and their performance will be interesting to observe.
Thanks again for doing all these experiments, Peter -- they're absolutely great(!), and the whole community owes you a lot. Have fun, stay safe, and we look forward to your next posts!!
Cheers,
- Ceilidh (W)


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## edisonr (Oct 24, 2003)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (Ceilidh)*

Ceilidh,
I think you are bringing up some very valid and interesting points (specially #2), but I don't agree with the marketing point of view.
As far as I can see, the point of pyce exercise is to find out how the dampers that are normally used to upgrade the suspension in ours MK4's behave; not to find the best replacement ever. Now, if you look at the options we have (for lowered springs) are Bilstens TC, HD and Sports; and Koni adjustable. Looking at the prices you might run into something like this (estimate including shipping):
Bilstein TC ~ $250
Bilstein HD ~ $420
Bilstein Sports ~ $450
Koni Yellows ~ $ 480
KYB AGX will fall between the $250 and $420 gap, running about $350 for a set (I found that price online). This price could give you and excellent damper set from factory with the bonus of a little adjustment. I don't think KYB AGX should be compared with the Koni Yellow just because they are adjustable. They both are in two different price ranges.
Please, correct me if the estimated prices I posted are sensible and if you know another damper that falls between the $250 and $420 category.
Thanks,
edisonr
EDIT: spell check



_Modified by edisonr at 10:04 AM 11-20-2004_


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## Ceilidh (Jan 7, 2004)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (edisonr)*


_Quote, originally posted by *edisonr* »_Ceilidh,
I think you are bringing up some very valid and interesting points (specially #2), but I don't agree with the marketing point of view.
As far as I can see, the point of pyce exercise is to find out how the dampers that are normally used to upgrade the suspension in ours MK4's behave; not to find the best replacement ever..........KYB AGX will fall between the $250 and $420 gap, running about $350 for a set (I found that price online). This price could give you and excellent damper set from factory with the bonus of a little adjustment. I don't think KYB AGX should be compared with the Koni Yellow just because they are adjustable. They both are in two different price ranges.
Please, correct me if the estimated prices I posted are sensible and if you know another damper that falls between the $250 and $420 category.
Thanks,
edisonr
EDIT: spell check
_Modified by edisonr at 8:31 AM 11-20-2004_

Hello Edison,
Thanks for the note -- Sounds like I hit the wrong tone in what I wrote (that's what I get for typing at 2 am EST!), as I'm in complete agreement with what you say! So let me try to clarify (i.e., where we're in agreement (which is in everything you've just written), and where I'm still feeling a little cynical (which is in something else)....).
As you correctly point out, Pyce is trying to find a good quasi-OEM damper that, when fitted to a car with stock springs, can yield excellent ride comfort and a noticeable improvement in overall handling. The KYB certainly does fit the bill here (at least judging from early Pyce reports), as it's affordable, has a nice compression curve, and appears to have a rebound level that's higher than stock but not so high as to cause significant comfort problems (we're still waiting to hear from Peter about what it's like over time on the concrete, but for now all indications are still favorable). In addition, there's (as you very nicely put it) the added bonus of a modicum of adjustment, which a person can use to mildly adjust for personal taste, or to compensate for mild wear, or to tailor for usage on a 2.0 Golf vs. a GLI Jetta. And once again, it's nice that the basic range is at a good spot -- with the Konis, it's very possible to be so far away from the ideal damping that the customer will never experience how good the ride/handling compromise can be; with the KYB, it's impossible to get away from the "good zone", as the adjustment range is so small.
That being said, there are some things about the KYB that might be of interest not to you, but to (1) people who have not put as much research into the shock as you have, and who don't have as clear an idea of what they're really looking for; and (2) people like Peter, who are also looking for great longevity. So for the benefit of those people, let me try to clarify what I tried to write earlier:
1) First off, as edisonr says, the KYB's look pretty nice for stock-spring use, near-OEM comfort, and somewhat higher-than-OEM handling. If that's what you're looking for, do consider them!!
2) If your goal deviates from #1, however, there are some almost-but-not-quite misleading statements in the KGB literature (nothing that would incur a fine from the feds, but they're just barely on the safe side of things), and newbies in particular should be aware of them. For example, if you click on the KYB website http://www.kyb.com/products/detail.php?ID=4
you read that
"AGX Sport Adjustable Shocks and Struts allow drivers to adjust dampening to match specific driving conditions quickly. The AGX Sport Adjustable Shocks and Struts have manual four or eight stage adjustable dampening which makes it completely on-the-car adjustable within minutes. With its competition grade engineering and construction, AGX Sport Adjustable Shocks and Struts are perfect for sport enthusiasts and high performance drivers."
Now, if you're a marketing professional, the above blurb is almost hilarious in its slavish adherence to textbook technique.







In 64 words of prose, it manages to state the full name of the product no fewer than 3 times (using up 18 words in the process), and it mentions some form of "adjust" three additional times. That takes care of the marketing objective of instilling an impression through sheer repetition. It also uses the non-engineering term "dampening" that tends to be preferred by the non tech-savvy, and they manage to crowd in the words "perfect" and "high performance" as well (this on a website entitled "KYB World-Class Shocks and Struts". All that's missing are references to "quality", "first-class", "teamwork", and "reliability" to complete the list of Marketing 101 cliches (presumably the writer ran out of space -- oh, but look: the rest of the website is full of these terms!)).








Anyway, there's nothing wrong with a company being proud of its work, but on a more serious note, it's very possible to misinterpret what KYB writes. I should stress that nothing in the above blurb is actually incorrect -- indeed, on a line by line basis, it's a commendably truthful overview of the shock (although I'm mocking the blurb for its heavy use of manipulative marketing principles (and yes, I once had a job that involved writing and approving such things), it really is a brilliant piece of work: I would hire the person who wrote it in a second!). The problem is in the overall impression: a newbie reading the KYB lit and seeing the word "Track" on the box (not you, edisonr, but someone much newer to the game) can quite easily come away with the impression that the KYB World Class AGX Sport Adjustable Shocks and Struts are competition-ready shock absorbers that, with a twist of a dial, can be readily converted from a plush-riding "street" shock to a firm, high-performance component suitable for hard street driving, or perhaps even light autocross or track use. A person would also be forgiven for thinking the shocks would work well with "competition-grade" springs and antiroll bars, and as such would make a nice complement to a set of "performance" springs and bars. But that's not what the advertising says (at least in a legal sense), and that's not what the shocks can (apparently) do.
a) Let's take the adjustability first: the range (unless something bizarre happened/ malfunctioned on Peter's dyno) is absurdly low: 7-8% on rebound is not that far from some manufacturers' tolerances on new shocks, and it's well within what one would expect to occur as a shock wears over time. It's not completely useless, as the different settings do make a noticeable change (and after all, we're mostly after "feel" in this game) -- but it's very, very limited. To see just how limited, we'll have to look at point (b):
b) Ok. For street use, what's the shock adjustment range you need to go from best comfort to best handling? It'll of course vary from car to car, but if we refer back to the Milliken bible (pages 810-819), we can find some figures for a compact sedan: for best comfort, the damping ratio is 0.15; for best handling, it's 0.45. Or put in English, when you adjust from best comfort to best handling (given a fixed set of springs, tires, masses, etc.), you need to increase the damping by a factor of 3. (That's assuming road use with stock springs -- if the springs are stiffened, the shocks have to go even stiffer; if the usage is smooth autocross track-work, then stiffer still might be in order....). 3.00X vs 1.08X : big difference.
c) Just to elaborate on (b) a little more: the "20 in/sec" curves on Peter's graphs show the KYB to be about 28% (i.e., 1.28 X) stiffer than OEM in rebound. Hence if the OEM damping ratio is 0.15, the KYB damping ratio would be 0.19. That's actually a useful step -- if you look at the performance vs. damping ratio curves in a suspension text (sorry, I have no way of scanning things in), the performance peak is pretty "fat", and 0.19 does get you a good part of the way there. So the KYB does do what Peter and edisonr desire -- give a stock car somewhat better handling while retaining a lot of comfort; it's just not going to perform wonders.
d) As a side note here: the 3:1 best handling / best comfort ratio would explain why the Bilstein HD's appear to be so punishingly stiff, and why Koni has a Red and Yellow range: the Bilsteins appear to be set up for maximum handling, and the Koni 2:1 adjustment range is not enough to cover the distance from best ride to best handling; hence the Red takes care of the low end, and the overlapping Yellow does the high...
e) By the way, if anyone is wondering why I've just said we need an enormous change in shock stiffness to effect a change in handling, whereas last night I wrote that a small change in shock stiffness has a big effect on springs and masses, here's the breakdown:
i. If the goal is to make a significant change in handling, then you need a very big change in shock stiffness.
ii. If the goal is to make a significant change in ride comfort, then a small change in shock stiffness can have a big effect -- if you're already near the ideal point. If you're far from the ideal ride point, small changes are hard to notice.
iii. The distance from ideal ride comfort to ideal handling is very, very far. (3:1)
iv. If the goal is to maintain the same level of ride & handling (whatever it is) while changing spring rates or masses (sprung and unsprung), then the shock setting must change with the square root of the change in rate or mass (i.e., a small change in shock stiffness can accommodate a big change in rate or mass) -- but that's simply to maintain a given compromise.
Thus if your goal is (like VW's) to maintain a consistent feel among many cars of different weights, you need a large assortment of close-but-not-quite-identical shock absorbers (or you can use the very limited adjustment of something like a KYB). But if your goal is to significantly improve the handling of the car, you need either a fundamentally much stiffer shock, or one that has a much, much wider adjustment range. Hence the verity in edisonr's point that the KYBs and Konis are in two fundamentally different classes.
.
3) As can be clear from reading this post, try as I might to be fair to KYB (the shock really does seem to fit what perhaps the majority of us really need -- good comfort, good handling, a bit of adjustment in a range that's useful for feel), I keep on slipping back into contempt towards their marketing. And for now, I think I'll maintain my suspicions: One of Peter's goals here is to find an OEM-performing shock that will last longer than ~40k miles; if that shock doesn't exist, then the easiest and cheapest course for everyone will be to simply buy the OEM shock from VW (or using VW part numbers and buying through a discounter) and replace it every few years. The KYB looks nice, and if its particular ride/handling compromise fits a person's needs better than OEM, then he/she should go for it! But if a goal is better than OEM longevity, then will it really last longer? And is it worth (in that respect) the extra money? (And the presence of a "lifetime guarantee" is meaningless in the shock aftermarket: people typically replace their shocks after 3 or 4 years, and sell their cars before the replacement set wears out; of those who keep their cars longer (or who wear out the shocks sooner) a large fraction will "upgrade" to a different brand, rather than incur the labor charges of installing a replacement that might go bad just as quickly; the remainder (those who actually use the warranty to get replacement shocks) are just a business expense...)
There are cases where a well-engineered product winds up with extraneous marketing fluff that don't hinder the overall quality (we once put an entire subassembly that didn't do anything on an otherwise high-quality product (and we didn't claim it did anything; we just pointed out that it was there) because marketing correctly told us that people would pay more money for the product if it had that assembly on it -- even if the assembly didn't actually work). But those are exceptional cases, and the best engineers tend not to stay in organizations where they have to regularly do such things. (Think about it: if you're good and you're proud of what you do, would you stay someplace that has you doing things that you think are stupid, all so that the company can make more money off naive consumers?) Maybe Japan is different, with their historical lifelong employment, but I would tend to doubt the differences are extreme -- the best Japanese engineers I've met are every bit as proud and quality conscious as their western counterparts, and the young university graduates don't want to work in places where they'll spend a lifetime having their dreams and principles thwarted.
So what do we have with the KYB AGX? If Peter's reports are not the result of an anomalous malfunction, we have a "World Class" "Adjustable" shock that's barely adjustable (but which features the most enormous, garish adjustment wheel in the entire industry); we have a beefy "competition grade" shaft that impresses onlookers with its size (ooooh! You can just tell these are REAL Heavy Duty Parts!!!) but which unnecessarily adds weight and uses up fluid reservoir volume); ditto for the shock body, which is on a non-track shock but is actually bigger than a Bilsteins ("heavy duty!" again, only this time we add unsprung weight); and we have advertising literature that vigorously employs tactics usually reserved for combo kitchen-aid products.
So, does the presence of all these kitschy (and borderline misleading) product features mean that KYB has not gone and specced expensive, high-precision and highly-durable materials in the internal valving where nobody can see it and where the benefits won't be observed for 30 or 40 thousand miles? Are the hydraulic seals similarly of hard-to-source but extremely durable elastomers that will put up with years of temperature reversals and fluid contaminants without hardening and leaking, and will KYB regularly police its suppliers to make sure cheaper substitutes aren't being used? (with our products, every time we turned around the factory would substitute a lower grade material in some critical component -- if you care about these things, you have to pay for expensive people to keep track of everything and sniff out all the manufacturing weirdnesses that arise) And has the design process been vetted by project managers willing to go toe-to-toe with the cost accountants and product launch planners, to ensure that adequate time and resources have been spent to ensure top quality despite the cost in expensive engineering hours? ------ Perhaps. Perhaps the KYB is truly an exceptional quality product, that simply has some marketing fluff added to it to increase sales......But perhaps it's merely a very good product, of OEM Sachs-Boge reliability and longevity, but more expensive because of the successful marketing.....








Anyway, as edisonr points out, if you're looking for an essentially stock shock with a little more damping (enough to improve handling a modest amount, but not so much as to destroy ride comfort), and if the idea of adjusting for feel appeals to you, then it's looking like the KYB is a good possibility.
Cheers!,
-C


_Modified by Ceilidh at 12:40 PM 11-20-2004_


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## pyce (Nov 7, 2001)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_1) Please forgive me for being a wee bit cynical……

Winston, you do not have to excuse yourself! This was the whole reason we started this thread – so we can look below what is written “on the box” of all these products and see if we can learn something more. Actually, it is extremely important to have someone who can talk with no fear and no bias. We all are not here to please each other or to accommodate each other views – our goal is to find out truth! Truth some times (many times, actually) is a painful thing and takes some “victims”, but we have to be determined to go all the way to the end even if this will cost us some problems of various kind. I think you are doing absolutely great by saying what is in our mind, keep going please! ……. On another note, related to this whole first part of your post – I had the pleasure to work in Japan and spent in total four and a half years in South-East Asia for work, and have to say that those people (the Japanese) managed to impress me the most with their engineering and design. One of the things that impressed me the most (and it is funny how it comes handy here) was that they do actually make almost everything with the smallest possible dimension, weight, materials, labor, etc. Example that comes to mind here was this stupid plastic box that had a “living hinge”. We had to design it, they had to bring it to production, therefore specifying material thickness, material composition, sizes, etc…. So, once we gave them the outside surfacing, they spend a lot of time calculating (and testing) the thickness of the sole living hinge, because they have found that the best compromise between how expansive the product will be, how expansive the tool would be (that particular are of the living hinge is very “touchy” on the tool! Looks like a knife small gain in thickness can increase longevity of the tool by much, so cut costs!) and how long this box has to operate, etc – so they found out that the best compromise would be to open this box exactly 800 times, and after that the plastic living hinge should break! Meanwhile we were drinking sake outside, enjoying life and thinking that they are crazy….. Fact is, the tools were designed, we went for production and every single box tested made from 802 to 812 openings before it broke! Needless to say that I can fill up your in-box with examples like that from all the experience I had working with them. I even developed this great desire to be like them, but realized that I could never be. Anyway, why am I saying all this? Simply because my experience with them makes it very hard to believe that they actually over-designed the damper we are talking about here. Now, this said, we all know there is no perfect country with perfect people and if Toyotas and Hondas are great reliable cars does not really mean that everything that ever came out of Japan is as good as that – but in general lines here, I am honestly having hard times believing that the damper was over designed (looking at the dimensions, of course). It is just so against their philosophy and their concept, not to talk about the pride that you mention – they have that a lot in themselves! Basically, I feel like digging little bit more into this KYB AGX damper and why is it done in the way it is done, because it is simply against all the impressions these people left in me after those years spent there. I do NOT disagree with you, I have hard time to agree (to put meaning) with the facts that the shaft, body, knob are bigger and that the “dampening’s range” is such a narrow and therefore does not coincide fully with what is written on the box…….. Speaking of which (the box) – your points were the exact reason I took the picture not only of the damper, but of the box too – because those words there kind of hit me too. It was little bit too “pushy” to put Street, Strip and Track in one. Yes, it sells the product big time, but only the first few. After that people (like us) get together, exchange info and soon one or two of these words on the box are simply ignored….. 
Anyway, before someone jumps on you to criticize some of your words, I would like to make a point here. To all the people who disagree with Ceilidh on specific sentences – Please do read the whole post(s) when he writes something and then reply or judge! I know they are long and perhaps “too deep” for many of us, but only if you read the whole thing you could realize that he is bringing out not only “bad points” or criticism. Try to read sometime between the lines. A sentence per se may mean one thing per se, but when used in a large and complex write up, it may change meaning to support the whole argument. I think this is the whole reason his posts are rare but rather long, because complex thoughts can not be expressed in short. At the same time, enlarging the write-ups is always risky because someone may concentrate on specific sentences and disagree with it and not being able to see the big picture. Take your time and read everything he writes at once, please!









_Quote, originally posted by *Ceilidh* »_2) Of course, there's an upside too: if we stay with the Japanese marketing/engineering stereotype, we also expect there to be some fairly subtle and well-thought out engineering that meets our *real* needs without our particularly realizing it; and there appears to be some of that here as well:
There appears to be about 15-17% adjustability in the compression and perhaps 7-8% in the rebound -- not a whole lot, but let's look at this range in a little more detail; when we do, we see there's actually some real benefit to what KYB is doing, and in effect they're sort of helping us despite ourselves………….
……(Or it put it in completely non-mathematical terms, a small change in damping can accommodate a big change in spring rate, or vehicle & wheel weight.)

This is a very good point! I like the “Helping us despite ourselves” part







They basically did not leave it to us to play “tuners”, which is in a way a very good thing! Some may remember the endless days when we were trying to find out how does ever ¼ turn on the Koni rears affectes this and that, and therefore had to also take those damper out more than I would ever desire…… at the end to find out what – that it is all pretty sensitive, and as Winston said many times – it is very easy to never catch the “sweet spot” unless you do small adjustments each time, but small adjustments each time is simple, plain PITA because it is so much time consuming, to a point that we found some “average” settings that somehow suit our needs and call it a day. Were those externally adjustable, I would testing every one degree of turn (!) but there is no way in the world this is gonna happen if I have to continue removing those each time. So, basically it is nice ot have external (but that is something everyone could figure out) but what is really nice (watch out – this is for my specific case only!) is the fact that they (KYB) did actually do some real testing (perhaps) and got us some very nice valving (or whatever it is) that makes this damper “the less uncomfortable” from the “sporty” brands. So, the bad thing is that racer will have to skip it, and therefore the word “Track” on the box is somehow misleading, but the “Street” and “Strip” fellows (like me) are very welcome to apply, if the desire is “Sport*y*” feel and performance. Yes, not a full “Sport” but “Sporty”. Of course, all this music may change dramatically when larger wheels, stiffer tires and lowered stiffer springs are used! Beware! Again, do not want someone to blame me his combo is freaking stiff with these dampers (using more than stock tire size and springs)….. the answer for that would be: “Put Bilsteins and it will be even stiffer!”… But to put Winston’s point into perspective – There is not problem with the fact that they kind of matched them pretty well to our stock cars, and there is no problem with the fact that they gave us some sort of adjustability – the problem is that this product is marketed “alla” Koni Yellow, which could offer much more “track” and not bad “street”, but it is not any near the Koni’s capabilities when it comes out to the higher control level at the highest settings.


_Quote, originally posted by *Ceilidh* »_3) Bottom line, your suggestion (in a later post) is plausible, that maybe the adjustability of the KYB is primarily there to adjust the shock to different models of the Golf/Jetta IV line.... 

Something else I was thinking before…… maybe it is also designed this way (narrow range) just to compensate for wear through the years? I mean, after a year of driving, you start feeling them little bit weak – bum – make one click and back to basic and seven more years to go, LOL










_Quote, originally posted by *Ceilidh* »_4) Peter, I'm not sure if I'm interpreting your graphs or the above comment correctly, but it seems to me that the KYB's are significantly softer than the Konis in compression, but firmer than the full-soft Konis in rebound (though significantly softer than the full-stiff Koni rebound setting). In this light, I would interpret the better comfort of the KYB (when compared to the full-soft Koni) as at least in part (and I kind of think primarily) due to the difference in compression. The "knee" here certainly plays a role, but at least on my GTI there's certainly an over-abundance of compression, and that (on my car) appears to be the main cause of discomfort.

I did not put that one very well I guess. Toward the end of that quote, it says (the curve, the lack of “knees”) and should have been (the curve AND the luck of knees). Basically wanted to point out what you are saying, that the compression (the curve of the compression) is major factor in the comfort department. But I am also pretty sure that the “knee” makes huge difference, because if we look back at the TC duynos, the compression (the absolute compression values) of the TC is much lower than the one the KYB provides, but the TC provided significantly different ride quality…..

_Quote, originally posted by *Ceilidh* »_6) As a final note: I have reservations about the KYB's longevity. Yes, they're an OEM manufacturer, but so is Sachs-Boge, and the OEM shocks don't last all that long……. 

I also have reservations. I am in a situation that doubt almost everything that everyone sells and says and so on. Only time will show us….. But one note I would like to make here, perhaps it is meaningless, but just came in my mind – The OEM stuff was done by Sachs-Boge, but I guess also they were told that it has to cost such and perhaps last such, and the Sachs-Boge people came with such damper….. Now, ideally, when you buy an aftermarket damper that is “more expansive”, regardless of who made it, I do somehow expect to be done differently, just because they put more money into it and are targeting higher prices too – so perhaps there is hope (from my naïve logic) that KYB can do better than our OEM dampers (in terms of reliability) if they wanted so…. 
I thank you for the time to write all this. It is priceless reading for me!


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## edisonr (Oct 24, 2003)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (pyce)*

I would like to start saying sorry for my response, I don't want to ruin the excellent work done so far. This thread is so informative that you could get very involved. 
My case is, I'm searching for a set of dampers to replace my OEM in combination with a set of lowering springs (1.5" drop). I am the kind of person looking for street applications and sport*y* response, without breaking the bank. I also like to have the facts before I make a purchase, especially suspension, since it will affect they way my car rides. Now with that in mind, so far the KYB are the choice. I do understand Ceilidh point about marketing, people would tend to compare them to Koni Yellows, and expect the same characteristics at a much lower price (basically a lot for less). This never happens in real life and you always get what you pay for. BUT, with facts in hands, I could realize the limitations of the KYB and know what to expect.
I just wanted to add another factor to this thread, the money factor, which could affect the decision of the person reading this thread.
I think I am going to step back and watch the game from my seat; but I am going to be waiting for the home run


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## pyce (Nov 7, 2001)

*Re: KYB AGX - Some more driving aournd....*

So far put 200 miles on them (long drive last night and some done today) and it does not look bad. The concrete is not so bad, even if it is not stock. Just few minutes ago did the accelerometer tests as well (but can't post the pictures now) and they do look pretty good. Basically the graphs do look the best so far that we have come out with, and it feels that way too. The striking part is this .... two actually:
1. The graphs from full soft to full stiff "almost" do not change! In same areas actually the full stiff is "better" (less vertical accelerations) than the full soft! I mean, later on you will look at them and someone may even think that all it was done was a slight tire pressure change....
2. Now, here is the real kicker - while the comfort does not suffer much, there is very noticeable improvement in feeling while doing slaloms, etc when the dampers are on full stiff vs. full soft! It is a change that the dyno data would never suggest, nor the accelerometer would let you think of! I know it continues to sound nuts, but I am trying very hard to be unbiased. Someone out there with these - come and tell me I am not dreaming, please!








Let's see how the longer trip would go. We will put aprox. another 300 miles before end tomorrow, so there will be more to talk about. There are some really crappy roads the trip goes through, so tomorrow will decide whether to get the fronts as well..... 
On another note - the car became boring to drive again. I was just getting used to the bone stock setup, which is so nicely designed so you feel like you are "driving" even at lower speeds - and with just replacing these two rears, the car got so much in control again - the feel of driving is going away at the slower speeds. It makes you feel you no longer need to concentrate or apply skills as to move - it just goes where you point it with no drama. It is little bit like putting tires on a snowboard and bringing it to the street......


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## pyce (Nov 7, 2001)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (edisonr)*


_Quote, originally posted by *edisonr* »_I would like to start saying sorry for my response, I don't want to ruin the excellent work done so far….. 

You do not need to feel sorry, you are not ruining anything! This is a free-speech board and it is very important that we all speak what is on our mind – only then we can have healthy debates from which some truth comes out. It is way better than if we just all agree and live in darkness just because we are afraid to say what we think.

_Quote, originally posted by *edisonr * »_ ……I do understand Ceilidh point about marketing, people would tend to compare them to Koni Yellows, and expect the same characteristics at a much lower price (basically a lot for less). This never happens in real life and you always get what you pay for. BUT, with facts in hands, I could realize the limitations of the KYB and know what to expect.

This is very good point! That is exactly what he (Winston) was after – why advertising them as “Koni but for less” when they are not. The good part is, thought, that small amount of people like me are not after the “Koni for less” but perhaps “Less-Performance-Than-Koni for less” because not full-out performance is needed in my specific use of the car – and here the KYB are coming really handy, despite the “wrong” advertisement for our specific platform. And this is why you can hear the two voices – one is “angry” (him) about them selling it for what is not – the other one is “happy” (me) that the “mismatched” marketing is nicely helping my case in satisfying my personal desire of “sport*y*” car for everyday use.


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## Ceilidh (Jan 7, 2004)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (pyce)*


_Quote, originally posted by *pyce* »_
....I had the pleasure to work in Japan and spent in total four and a half years in South-East Asia for work, and have to say that those people (the Japanese) managed to impress me the most with their engineering and design. One of the things that impressed me the most (and it is funny how it comes handy here) was that they do actually make almost everything with the smallest possible dimension, weight, materials, labor, etc.........so they found out that the best compromise would be to open this box exactly 800 times, and after that the plastic living hinge should break!......we went for production and every single box tested made from 802 to 812 openings before it broke! Needless to say that I can fill up your in-box with examples like that from all the experience I had working with them. I even developed this great desire to be like them, but realized that I could never be.....


Hi Peter,
Great post, and thanks very much for setting things in context for everyone (and also for defending my neck!). I suppose at this point I'd better explain a little more about marketing/engineering concerning Japan, lest more people think I'm criticising the whole country (and as usual, I'll number the points, just to keep things tidy).
1) I once spent a pleasant afternoon speaking with members of a Japanese engineering team whose careers were spent designing the ball of a ballpoint pen. Not the pen, not the ballpoint housing, but just the ball itself. In that company, there were 6 fulltime engineers, all devoted to the ball; collectively there were probably about 100 man-years of experience on ballpoint pen balls, and the team contained some younger members who were being trained to carry the flame in the future. So I know exactly what you mean about Japanese engineering prowess, and believe me, I too have incredible respect for it!
2) The issue I'm referring to with the KYB is not the pure engineering per se, but the confluence of engineering and marketing. Japanese engineering is rightfully respected worldwide, but what's perhaps less known is that Japanese marketing is among the best in the world as well (some would say they are THE best in the world, in fact). And when you mix worldclass engineering with worldclass marketing, you sometimes get some curious things.
To cite an example, if you buy a new bicycle these days, it's almost impossible not to get one with Shimano componentry (Campagnolo is holding on in high-end road bikes, and SRAM has fought its way into a growing niche with its shifters and ancillaries, but basically everybody else is now dead or tiny). During Shimano's rise through the 70's and 80's, it came out with a host of elegantly-engineered innovations that sounded absolutely wonderful, and which accomplished virtually nothing useful (anybody remember "Biopace"?). Each of these innovations were masterful marketing/engineering plays: they were typically patentable, harmless, useless, but hard to argue against, and collectively they painted a picture of Shimano the great innovator. During this same period, Shimano instituted a policy of obsoleting all its older componentry every time it revised a Groupset (about every 3 years), which was in marked contrast with the then industry-norm (typified by Campagnolo) of extreme parts longevity and compatibility over the years; as a result, every time Shimano revised its group (adding a new "feature" with each one), people had to junk all their old parts and buy new ones. This cycle brought Shimano lots of cash, which funded a whole host of legitimate engineering research (I should hasten to add that amongst all the charlatan stuff, Shimano also did some amazing legitimate work to make gear changing much easier than it had hitherto been), and the rapid obsolescence meant that parts durability (Campagnolo's strong suit) became largely irrelevant. Moreover, the systems approach needed to make Shimano's gearchanging effective meant that everything on a bike had to be Shimano (particularly during the 80s and 90s), which drove out all the small niche manufacturers of derailleurs, freewheels, chains, shifters, etc.....
Hmmmm. This is going to take too long, and this isn't a forum about bicycles! So let me jump ahead to the main point: when any company ties state of the art engineering to state of the art marketing, it is going to do things that it judges are best for its own longterm success -- not for the success of the industry, nor for the benefit of the consumer. And although a group of engineers might be world class and impassioned about quality, that doesn't mean that marketing is not going to steer them in certain directions. (With bicycle componentry, we now have parts that mostly function very well, but which wear out at rates that would have been considered scandalous in the 60s and 70s...)
3) Let's switch to a car example. Everyone's seen how Lexus has ripped the guts out of the German luxury car industry, and how in a few short years it's become an equal player with Mercedes, BMW, etc. Lexus deserves its success -- it's done an absolutely fabulous job, and its cars are truly high-quality products that do a better job than almost anything else at meeting the needs of its customers....but let me ask you something: how many old Lexuses do you see on the roads? When's the last time you saw an original LS400 proudly going down the street? In contrast, how many '60s, '70s, and '80s Volvos and Mercedes do you see driving around?
If you tear apart a Lexus, you find a lot of interesting things. The seat frames, for example, are unpainted, and typically there's surface rust -- that rust has absolutely no effect on the function of the car (it's just a patina), and leaving off the paint is a very wise marketing/ engineering decision -- there's a real cost savings in the omission, the customer will neither know nor suffer for it, and the money saved can be spent on something that the consumer actually cares about (like brake pads that don't make a lot of dust). Does that make for a better car? In the context of what a new Lexus owner wants, absolutely, and business school case studies literally use Lexus vs. Mercedes as an example of the correct and the incorrect way to marry worldclass engineering to worldclass marketing. Lexus, with parts that are only just barely good enough for its target customers (but with *all* the parts just good enough, with nothing inadvertently left out) is the "correct" way to do it; Mercedes, with a lot of extra engineering (they paint their seat frames!) on things the original customer will never see (so what if the engine is good for a quarter-million miles? -- by then, the car's on its 3rd or 4th owner, and that owner is never going to buy a new Mercedes...), and omissions on things the Mercedes engineers thought were unimportant (e.g., dustless brakes), is the "wrong" way.
But again, how many old Mercedes do you see on the road, and how many old Lexuses?








4) Peter, what I'm getting at is that although Japanese engineering is world-class, that doesn't mean the resulting product is "good"; it only means (because Japanese marketing is typically world-class too) tthat it's good for the company. When what's good for the company is also good for the customer (as it appears to be in the case of Lexus), that's great. And arguably we can put KYB in this category too: as you and I have both independently found, when it comes to suspensions, sometimes what we really need is very different from what we think we want (in particular, the closer we are to stock, the better off we are), and the KYB in effect forces us into goodness. But where we have to be careful (and here I'm not talking to you Peter, as you know this point very very well!) is when we begin to ascribe other, hidden attributes to a product because what we see on the surface is so impressive. With a German product, these hidden attributes are often there -- mostly because German marketing has historically been just awful at coordinating with engineering; with a Japanese product (because the link between marketing and engineering is so good), I'd be less confident. That's not a knock on the Japanese -- in effect, it's a compliment, as we in the U.S. are literally trying to emulate them in their ability to marry marketing and engineering -- but it does mean we have to be really careful at discerning exactly what the product is promising us.
And on this note: absolutely nowhere does KYB claim that its shocks are particularly long-lived.
5) And just by the by, to give an example of how notoriously bad German marketing has historically been (and by "marketing" we mean the actions a company takes to ensure its products are what its customers truly desire): Koni has tested each of its shocks on all the major variants of every mass-production application (that's why there's typically a lag between when a new model/variant comes out and the appearance of a matching Koni) -- how much work would it take to simply list on the Koni website what the ideal setting was on each variant tested? Would this increase the amount of customer satisfaction among Koni users? Absolutely! Would a Japanese company in Koni's position publish a detailed guide? Probably....

_Quote »_
Anyway, why am I saying all this? Simply because my experience with them makes it very hard to believe that they actually over-designed the damper we are talking about here.


Just to wrap up this point: I too find it hard to believe they over-designed it too, from an engineering perspective (no doubt they know exactly how beefy everything has to be in order to actually work). But I can readily believe that KYB marketing has done extensive market research to determine how many extra sales they get by going oversize on the shaft and body, and the KYB engineers have done a masterful job of designing the shock around those parameters...









_Quote »_
.....But one note I would like to make here, perhaps it is meaningless, but just came in my mind – The OEM stuff was done by Sachs-Boge, but I guess also they were told that it has to cost such and perhaps last such, and the Sachs-Boge people came with such damper….. Now, ideally, when you buy an aftermarket damper that is “more expansive”, regardless of who made it, I do somehow expect to be done differently, just because they put more money into it and are targeting higher prices too – so perhaps there is hope (from my naïve logic) that KYB can do better than our OEM dampers (in terms of reliability) if they wanted so…. 


That's an excellent point, and one I should have thought of. As the KYB appears to be such an excellent fit for you, I hope this proves to be true!
Cheers Peter (and edisonr)!
- Ceilidh


_Modified by Ceilidh at 7:53 PM 11-20-2004_


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## Cadenza_7o (Jan 23, 2001)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (Ceilidh)*

Winston, Pyce - 
your drift into the marketing/engineering and cultural differences between the Germans and Japanese was really enjoyable to read. And Winston, I agree with your POV about the Japanese marketing all the way. Excellent observation! MB and BMW learned from Lexus that it wasn't all about handling, performance. Heck the SC430 is one of the most boring car to drive but people still lined up for it. In fact, the only Lexus I find fun to drive is the IS300. It seems that Lexus spent more time with their focus group and found out that, for the US market, having a formidable suspension for speeds in excess of 100 mph is a waste of engineering effort and financial resource.
My German Prof once said, "When I was in Japan, I felt really at home... in Germany. It was scarry!" These peoples are so similar in many respects and they are drawn to each other in some ways. Yet, they're so different too. 
I hope Toyota and VW merge someday. Man, that would give GM and MB something to worry about.







As for engineering, I still find that the Germans are better at putting originality, personality and interesting quirkiness into a product while the Japanese are much better at the execution of a product... manufacturing with cold, efficient quality.
Peter, I'm not sure if your quest for the ideal damper will ever end. Maybe it's not the damper... maybe it's the limitation of the twist-beam suspension and stiff stock springs coupled with a light rear-end?
I think your quest will end up with one of this!


















_Modified by Cadenza_7o at 3:52 AM 11-21-2004_


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## Cadenza_7o (Jan 23, 2001)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_If you tear apart a Lexus, you find a lot of interesting things. The seat frames, for example, are unpainted, and typically there's surface rust -- that rust has absolutely no effect on the function of the car (it's just a patina), and leaving off the paint is a very wise marketing/ engineering decision -- there's a real cost savings in the omission, the customer will neither know nor suffer for it, and the money saved can be spent on something that the consumer actually cares about (like brake pads that don't make a lot of dust). Does that make for a better car? In the context of what a new Lexus owner wants, absolutely, and business school case studies literally use Lexus vs. Mercedes as an example of the correct and the incorrect way to marry worldclass engineering to worldclass marketing. Lexus, with parts that are only just barely good enough for its target customers (but with *all* the parts just good enough, with nothing inadvertently left out) is the "correct" way to do it; Mercedes, with a lot of extra engineering (they paint their seat frames!) on things the original customer will never see (so what if the engine is good for a quarter-million miles? -- by then, the car's on its 3rd or 4th owner, and that owner is never going to buy a new Mercedes...), and omissions on things the Mercedes engineers thought were unimportant (e.g., dustless brakes), is the "wrong" way.
But again, how many old Mercedes do you see on the road, and how many old Lexuses?









My GF works for Nissan and she said that their engineering department recently received a Touareg, BMW X3 and the new 5-series. I wonder what they'll find when they're finished tearing down these vehicles.








Maybe it's just my observation but people also hang on to their Benzes because they have personality... and the romance and history of Mercedes Benz. I can tell you that I would love to hold on to an old Beetle or Karmann Ghia than a new Lexus ES330. Of course, the Lexus is high-tech and luxurious but it still lacks a certain "Je ne sais quoi".










_Modified by Cadenza_7o at 4:00 AM 11-21-2004_


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## Ceilidh (Jan 7, 2004)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (Cadenza_7o)*


_Quote, originally posted by *Cadenza_7o* »_
......Maybe it's just my observation but people also hang on to their Benzes because they have personality... and the romance and history of Mercedes Benz. I can tell you that I would love to hold on to an old Beetle or Karmann Ghia than a new Lexus ES330. Of course, the Lexus is high-tech and luxurious but it still lacks a certain "Je ne sais quoi".








Good point, Cadenza!! Personality & history is why I still have a '60s MGB sitting in my parents' garage -- lots of character, not exactly the world's best engineering (e.g., there's still structural wood under the seat frames!).
- C
P.S. Cadenza, are you still using a RSB with stock springs? Are you still happy with it? (Thanks!)


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## alexb75 (Dec 29, 2002)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (Cadenza_7o)*

Very cool discussion guys...
First, Winston:

_Quote, originally posted by *Ceilidh* »_But again, how many old Mercedes do you see on the road, and how many old Lexuses?

Well, I *TOTALLY * agree with you on the marketing side of things, Japanese are way better. However, I disagree about engineering quality, Lexus LS400 has been NUMBER ONE for a number of years in terms of longevity and care-free maintenance, those cars are extremely reliable. The reason we don't see older ones much around is that the earlier ones were not that good, and that MB and BMW still have much better resale, image and people tend to want those older ones more. 
In my experience, Japanese cars have been AMAZING for street driving, not too aggressive drivers and they don't break down if you don't push em. German cars break MUCH MORE for average drivers, but are better for aggressive driving types as they're sturider. To give you an example, all the Hondas and Toyotas owned by my Dad and his friends have RARELY been to any mechanic EVER... my VW and my sister's BMW (and all of our friends) have had LOTS AND LOTS of small problems that needed to fixed at the dealer. However, my Honda needed pads, clutch, rotors, etc... starting with less than 20K miles on the car as I pushed it very hard, but I out lasted 3 sets of Honda pads and 2 sets of Honda rotors and a Honda clutch on my VW and I have 45K on it http://****************.com/smile/emthup.gif 
So, IMO, the Japanese cars are engineered for _their intended use and intended use only_, as Peter mentioned, those boxes were designed to break after 800 times and they all did. German engineering builds something strong so even if u push it to 2000 times, it *"MAY"* last but then it may not last 200 times either, hence LESS CONSISTENT. 
Back to our own topic








*Peter:*
A few questions:
1. Did u install them with their own bumpstops? If so, how were they different than VW bumpstops “B” or “C”?
2. Do you feel any difference in body roll on KYB vs. OEM? 
3. What sort of Koni rebound setting is closest to KYB stiffest (if any)?
-------------------------------------------------------------------------------
On another note, I went back from 1 turn to 3/4 turn on rear Konis the other day and the difference, as mentioned already, is HUGE. I still haven't tried anything below 3/4 turn as I am on the handling side more than comfort... but it seems that 1/4 turn did the comfort trick for me - which is all you get with KYB softest-to-stiffest... which is kind of useless for my application but maybe perfect for Peter.
It again comes down to application and how each shock is marketed and for what segment. We all agree that Koni Yellow and Biltein HD/Sport are marketed properly for their intended use.... but KYB seems to be the shocks for those who cannot tolerate Koni/Bilstein stiffness but need better control (Grand Touring), so maybe Peter can finally be happy with his last purchase


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## Ceilidh (Jan 7, 2004)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (pyce)*

Hi Peter,
Favour to ask:








1) Remember that comparison plot you made of TC/Koni Soft/Stiff/OEM at 18.00 in/sec? Could you please do it again, only this time with the following shocks?
1) OEM
2) KYB
3) TC
4) Koni Soft (please leave out the Full-Stiff)
2) And if you're feeling up to it, could you please also overlay the 4 shocks on a Force vs. Velocity graph (the usual layout, with velocity on the horizontal axis and the force on the vertical); and for purposes of clarity, could you construct the graph using the following data:
1) compression force vs. velocity from Upper Left quadrant of 18.00 in/sec run (i.e., leave out the upper right quadrant, and entirely ignore all the other velocity runs).
2) rebound force vs. velocity from Lower Right quadrant, again from 18.00 in/sec run.
We lose some info on hysteresis this way, but it'll be clean and reasonably appropriate (we'll be getting the shocks at the start of compression and at the start of extension, which matters the most for handling and ride purposes).
No hurry at all (I imagine you'll be preparing for the holidays!), but thanks very very much in advance. Cheers!
- Winston


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## 2beirish (Apr 28, 2004)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (Ceilidh)*

I'm appreciative of the elegant and thoughtful language and the engineering analysis going on in this thread. I'm ready to re-suspend my stock Jetta 1.8T wagon, and, as always, in a quandary as to the system I purchase and install that meets mutually contradictory goals: increased resistance to sway/roll, more predictable suspension response close to the limit at speed, AND maintains some ride comfort so my saintly spouselink doesn't rub her forehead in frustration on road trips. I commute 120 daily miles over 3 mountain passes and roll through rain/snow/fog/ice, so I need a car with traction, forgiveness (potholes, off-camber roads, etc)and relative comfort. And even though it's heresy in the suspension threads, I wouldn't mind a little bit of drop from stock, maybe 1.5", so it stops looking like a dang June bug in heat, AND not to lose the correct suspension geometry in the front end: damn those McPherson struts! I've been a Bilstein fan for years because they're well-made, damping is usually close to what I want and I don't have the brainpower or butt sensitivilty to be rolling around under my car every weekend trying to find that elusive spiritual quotient of suspension harmony that adjustable Konis offer. and predictable at the limit. So I'll keep reading here, OR I'll just buy a new Subaru GT turbo wagon and forget trying to get this VW wagon to behave??







I DID think it was cute that in one of the KYB discussion notes KYB was translated into KGB: NOW the old Russian intelligence critters are doing suspension desigh??


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## alexb75 (Dec 29, 2002)

*Re: KYB AGX - Full Soft vs. Full Stiff ... (2beirish)*


_Quote, originally posted by *2beirish* »_I'm appreciative of the elegant and thoughtful language and the engineering analysis going on in this thread. I'm ready to re-suspend my stock Jetta 1.8T wagon, and, as always, in a quandary as to the system I purchase and install that meets mutually contradictory goals: increased resistance to sway/roll, more predictable suspension response close to the limit at speed, AND maintains some ride comfort so my saintly spouselink doesn't rub her forehead in frustration on road trips. I commute 120 daily miles over 3 mountain passes and roll through rain/snow/fog/ice, so I need a car with traction, forgiveness (potholes, off-camber roads, etc)and relative comfort. And even though it's heresy in the suspension threads, I wouldn't mind a little bit of drop from stock, maybe 1.5", so it stops looking like a dang June bug in heat, AND not to lose the correct suspension geometry in the front end: damn those McPherson struts! I've been a Bilstein fan for years because they're well-made, damping is usually close to what I want and I don't have the brainpower or butt sensitivilty to be rolling around under my car every weekend trying to find that elusive spiritual quotient of suspension harmony that adjustable Konis offer. and predictable at the limit. So I'll keep reading here, OR I'll just buy a new Subaru GT turbo wagon and forget trying to get this VW wagon to behave??







I DID think it was cute that in one of the KYB discussion notes KYB was translated into KGB: NOW the old Russian intelligence critters are doing suspension desigh??

It's very hard to recommend anything as people's perception of ride and handling are quite different. My advice to you and anyone else in search of a suspnesion is to try one, see if any local person has a setup you might be interested, buy them a coffee and get a ride in one. That's probably the best way to find out if you like a particular setup or not, and much better than all of advice you may get here. There are some general guidlines as what works or doesn't on our cars that you can get from these threads, but at the end of the day, what works for me, may not work for you. 
Having said that, since u have a wagon and may put stuff in the rear, I would recommend not to lower it too much as you lose too much in the rear and even people on Shine who had a wagon got rid of the rear springs since it was too low. I like my Sofsport and beleive me 0.5" is all you need to make it look decent. Shocks are the topic here, so you can get more info reading this thread.


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## pyce (Nov 7, 2001)

*Why there is a hope.....*


_Quote, originally posted by *Cadenza_7o* »_.....Peter, I'm not sure if your quest for the ideal damper will ever end. Maybe it's not the damper... maybe it's the limitation of the twist-beam suspension and stiff stock springs coupled with a light rear-end?......

Very good point! And I had almost resigned that it is like everyone here says – limitation of the twist-beam…… until we went for vacation in Europe and rented a sort of mid-sized (for their standards) Renault Laguna (something in the Passat’s league) and put several thousand miles on it in two weeks. The car was the most comfortable not luxurious car I have ever driven. It was pure pleasure and the handling would have suggested that it has some sophisticated suspension. This until some Spaniard cut our rear right tire with a knife in downtown Barcelona (the car was with French plates and I guess they do have some issues with that…. Could not find another reason for cutting our tire







). So, had to replace the tire and when took it off – what do I see? This:








Looks familiar?







And it is pretty clear how the beam is even closer to the end of the arms, which “should” make for even less independent suspension, and yet, that car was riding and handling in a very different manner. It may be ugly, may be whatever, but seriously, if I had an opportunity to buy it in USA – I would have got it right today. It was really some sort of magic mix of mild performance and outstanding comfort…… Few more things to note – The rear springs do have two blue dots, so I guess Renault also uses color codes like VW. And also, before someone spots the floor jack and asks how is it that I change flat tire with floor jack instead of the provided with the car mini jack – Want to point that the picture was taken later on when we decided to replace the cut tire with a new one and went to a local “wheel works”, so the picture was taken in that second moment







Here is also a picture of how that car looks like, just so you can see what I am talking about….








So, then few days later I found some books about suspension (Winston mentioned those books in the beginning of the thread and there are few pages posted as links) and if you go check this particular page, there is something interesting that perhaps explains little bit about why this car was particularly comfortable. I made the interesting sentences in slightly red, so you all do not need to read the whole page:
Page 05
(Note: All pages I have are posted as links in the beginning of this thread) 
The last sentence from this Page 05 link is in particular interest – *“Arguably, French manufacturers obtain the most appropriate compromise between the need of primary and secondary control, and hence the best ride.”* …… which did not explain to me exactly why our Renault was so fantastic, but at least gave me something to think about it. If the French can make a simple twist-beam rear work and be super comfortable, yet the car feels like a real grand touring, relatively flat cornering car - then perhaps it is possible, just the rest either do not know how or, most probably, as mentioned in the book, it is a strategy for each specific market and maker. Anyway, at this point I do believe that there is a sweet spot, but perhaps the more popular damper makers here (Bilstein, Koni, etc) have not really addressed specifically certain needs and have gone flat out in favoring performance first and the rest is “if you can not take it – do not buy it” thing. Perhaps that “red surrounded” text in the link also explains why some us have particular issues with German aftermarket dampers on our specific roads that are very far from what an Autobahn is (in terms of quality). So, if Bilstein and Koni do have the same part numbers for their internal (German) market and for our NA market – then perhaps we can be quiet sure they have “tuned” that stuff to suit them first, which automatically means that it may not suit few of us, like in the given example in the link of German cars doing not particularly well on British roads.
I have to go now, will answer to the rest later.


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## pyce (Nov 7, 2001)

*KYB AGX vs. Koni (alexb75)*


_Quote, originally posted by *alexb75* »_ 1. Did u install them with their own bumpstops? If so, how were they different than VW bumpstops “B” or “C”?

I wrote about this somewhere above, but guess the post was too long and you somehow missed the lines ….. The KYB AXG buffers are about 1” shorter than the “C” and are significantly stronger (harder) than the “C”. I would prefer the “C”, but as said before, the KYB has 13 mm shaft and the “C” are with smaller hole (designed for the 11 mm stock unit) so they can’t go it. Of course, we can make the hole bigger, but that will be at the very end when I finally decide which damper to use. I may take the KYB buffers and test them on the spring tester, to see how much more “spring rate” they do add when sitting on them, but it is not priority now. There is at least 2” lowering that could be done with the KYB and still the buffers supplied would not touch the body. 

_Quote, originally posted by *alexb75* »_ 2. Do you feel any difference in body roll on KYB vs. OEM? 

I guess ultimate roll (lean) would be the same, no matter what damper you put. It will just take longer for the body to “set” on the outer springs (if the dampers are stronger), etc. The whole point in having Sporty dampers is to be able to drive the car in a dirtier way, yanking it around harder, like fast and abrupt lane changes, etc. and the car still feels flatter, more in control, with slower body motion – so, basically you can afford not to be smooth and still get the car to transfer weight in a smother way. It is great “help tool” for people who for whatever reason correct their cars in the mid of the curves, etc. Here is some sort of a picture that shows in general what happens in a long 180 degree curve if OEM (or other weak or old unit) damper is used on the same car, with let’s say pretty soft springs. Then below there is the same curve, same car, but with “Sporty” dampers (or other type stiff damper):








So, what happens (in general):
1A – Car is flat and the initial steering input starts.
1B – Car starts leaning as the damper is “weak” and the outer damper does not have enough compression to slow down the “coming” fast weight to the left side. At the same time the inner damper does not have enough rebound to slow down the “leaving” fast weight from the right side.
1C – Car is fully rolled on its outer wheels (springs) compressing them the most.
1D – Car starts rolling back, towards the inner wheels, as the fully compressed springs in 1C do want to decompress now. Again, the damper is weak in slowing down that counter reaction, so we have the car slightly “coming back” towards less angle of roll.
1E – Car continues on the curve, so major part of the weight keeps going towards the outer wheels, therefore we have again a full compression of the outer springs (like in 1C). Perhaps this time the compression itself is not as hard as the first one, but it really depends on the radius of the curve, speed, corrections, etc.
1F – We have another “come back” here, like in (1D).
1G – We have another “compression” on the outer wheels (like in 1E) and all this kind of continues until the curve is over.
Again, this is in a very general terms….. So, we put the Sporty Damper and here is more or less what we have:
2A – Same as in 1A – car is flat and enters the curve.
2B – Car starts leaning, just like in 1B, but the damper is strong and the leaning is not as fast as before, therefore you can see the degree of roll is less for the same position in the curve and same speed!
2C – Here the car continues to increase the roll. In 1C we had reached to full compression on the outer springs, but here, due to the much slower roll, we are still half way from reaching full compression. Basically the stronger damper slows down the first roll.
2D – Car continues to go and rolls even further, but it is yet to reach full compression of the outer springs, so it is still in a phase of the first roll pointing towards outside of the curve!
2E – Car reaches full outer spring compression only now, almost twice as late as the car with weak damper! At this point, the same amount of roll had happened twice as slow, so it is to be expected that the “counter roll” would also occur twice as slow, therefore we have:
2F – Car starts rolling back (basically only now we have what happened in 1D)
2G – Car continues to roll back, etc….
So, in let’s say 180 degree curve, constant radius, with the weak damper we had 3 times roll direction change and with the Sporty damper we had only 1 roll direction change….. Again, this is just generalizing big time.

_Quote, originally posted by *alexb75* »_ 3. What sort of Koni rebound setting is closest to KYB stiffest (if any)?

Feels like 40 to 60% stiff on the Koni would match full stiff on the KYB AGX, but not sure. The Koni had been out for quiet some time and would not bet money on this. Perhaps have to put a Koni on the left and KYB on the right to tell more. The interesting part is – it feels to me (from memory) that if they are both set to “perform” the same (for similar weight transfer speed) – the KYB is noticeably more comfortable on all type of roads. More driving is needed to determine this thought….


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## alexb75 (Dec 29, 2002)

*Re: KYB AGX vs. Koni (pyce)*

Thanks for great response and explanation. I understand the roll thing and the picture does a great job of explaining it. 
I really doubt the KYB be 40-60% Koni stiffness, as I cannot do more than 50% on koni or it gets too stiff! From the dynos its more like 20-25%.


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## phatvw (Aug 29, 2001)

*Re: KYB AGX vs. Koni (pyce)*

Pyce, your diagram explains things very well. I never considered that during a long & hard turn, a weak damper would allow oscillation like that. I figured the centrifugal forces of such a turn would overpower any effects of the suspension once full compression had been reached.
Have you actually felt this oscillation? It has been so long since I have driven an oem setup hard...


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## pyce (Nov 7, 2001)

*Re: KYB AGX vs. Koni (phatvw)*

Phat, the OE dampers in my car right now are pretty new, so it doe snot go that way, but I am sure warn OE dampers (or perhaps a real blown damper) will go like this big time...... There is also something else - if you place the car nicely, smoothly - you can get away with the oscillations even if you do not have a strong damper (But then again, if speeds increase, not matter how smooth you are - you have to turn that wheel as fast as you can, so a stiffer damper will slow down the roll more, so at the end stiffer damper wins!). So, let's say you do not really feel this way (as on the OEM diagram) if you have good OEM dampers, BUT if you decide to keep correcting while turning, then you get the oscillations for sure, and therefore again - stiffer damper is our friend as it will allow us more abrupt corrections, etc. This was actually very well covered by Winston in the long thread time ago, but that time I did not have time to "picture" it, so perhaps got overlooked (Because we all have to admit that a picture gets more attention [and easier to perhaps comprehend] than 1.000 lines of post)







Through these pictures also cold be visualized how for example the Koni rebound settings behave - the stiffer the rear Konis are - the later in the curve the car will reach full compression, the more you can yank it around without paying much penalty, etc.......
As for the centrifugal forces of such overpowering the springs in compression - well, it is a spring, and wants to extend back to maintain its original status (shape) so it pushes back and it is the damper's duty to slow down those "desires". You have a point, because you perhaps observe what happens in your car while you drive - you are a smooth driver, know your limits, know the car's limits, know the curve and you will nicely place the car into that curve and the car will nicely "sit" on the outer springs at certain point into the curve and it will stay there through the whole curve, and then you will slowly open the gas and straighten the wheel and power out of the curve. All that went smooth because you were within the limits of everything together. Now, go over the limits, enter the curve at much higher speed and see what happens - the front wheels start sliding, you soon realize that you are going straight and away, so you very fast turn the wheel even more into the curve. That puts extra centrifugal force on top of the initial one. Your car loads the outer spring extra hard and the tire also gains some more traction and grips better and that results into you are now "closing" the curve more than needed.... So, you turn back the steering wheel some as to get to the ideal trajectory. That movement now helps the outer springs to unload some (and fast!) and by then, after all these fast movements in just a second or two - the car body rolling is already so great (because there were no stiffer damper to slow it down) - you are already fighting the car instead of fighting the curve and at the point priority number one becomes to gain back control, to slow the rolling with counter reactions, etc....... Basically all of this stuff that you know well how to do, judging from your reports after the track days.








P.S: Had to interrupt this post several times, so I hope it makes some sense by now


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## Cadenza_7o (Jan 23, 2001)

*Re: Why there is a hope..... (pyce)*

Peter - 
Regarding the Laguna... we would need some specs to compare it to the MK4 platform. 
- Track widths
- Wheel base
- Position of the engine & tranny in relation to the center of gravity of the car
- Curb weight
All these things affect ride quality.
From what I can see is it's a wagon (if that was the version you drove) and has a longer wheel base and wider width. Comparable to a Passat? All of which helps the ride quality. And don't forget you drove on European roads, which are better than the best of SoCal freeways from my experience of living 2 years in Germany, Switzerland and travelling through out Europe. Their surface streets can vary from one country to another, but most freeways/highways are excellent. 
If you place about 200 lbs in the trunk (increase sprung weight), the rear suspension becomes more compliant.


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## pyce (Nov 7, 2001)

*Winston - Cadenza_7o*

Winston - here is the first part of your request. For the second part I have to go to the shop again and construct the graphs. It is very easy, I learnt the basic on that software, so he let me go and do these things on my own now, but I just do not have physical time right now. It may happen tomorrow. I can actually "clean" them (the software has this capability) and show the requested from you Force vs. Velocity with only rebound or only compression (and of course both if needed) so the graphs are cleaner, with less lines and easier to read. I will go there again tomorrow to do so....








Cadenza - I will try to provide you with the data you requested. Sure, the Euro highways are much better, but they have crap streets too and that is where I value very much comfort. Besides, that car had 205-55-16 stock, pumped up pretty much (it is computer monitored pressure, big PITA when had to replace the tire!). Your points are of course very valid, but still, that car was significantly more comfortable than a Passat, also driven on those roads there! We will dig more into this later, have to go now....


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## TyrolSport (Mar 4, 1999)

*Re: Winston - Cadenza_7o (pyce)*

So the Konis at full soft have more OR less rebound than stock?


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## alexb75 (Dec 29, 2002)

*Re: Winston - Cadenza_7o (tyrolkid)*


_Quote, originally posted by *tyrolkid* »_So the Konis at full soft have more OR less rebound than stock?

Looks like it has much more compression but less rebound at softest!
It's a little wiered as my experience is quite different!


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## Ceilidh (Jan 7, 2004)

*Re: Winston - Cadenza_7o (alexb75)*


_Quote, originally posted by *alexb75* »_
Looks like it has much more compression but less rebound at softest!


Hi Mike, Alex,
Yes, that's correct -- it's something that's been bothering us for a while, and it's been consistent with our respective experiences on our rough Boston and (possibly) S.F. roads. That is, the compression/rebound ratio seems to be the root of the ride problems on my Boston roads, and might play a role in Peter's difficulties.
On my car at least, the high compression damping gives the car a quick, hard kick upwards on sharp bumps, after which the rebound (at full-soft) has trouble controlling the chassis motion. It's the reason my car is actually more comfortable at 1/4-turn (rear shock) than it is at full soft: The upward kick is there regardless, but whilst at full-soft it's followed by a quick series of little bounces, at 1/4 turn the rebound's enough to snub it down and damp out all the after-motions. (At still higher rebound settings, the snubbing action is so sudden that the upward kick is followed by a hard jerk, which becomes uncomfortable again...)
(Alex, you probably haven't noticed this effect because the British Columbia roads are so nice!







I can go miles without experiencing the above (and the car's great at the normal broken pavement we have around Beantown), but then I hit certain highways that have the right kind of ridges, and suddenly it's very apparent...)
One reason I've been so interested in the Koni Red is that its compression damping is supposedly (judging from Koni's generic graphs) about half of what it is on the Yellow. That would put it basically at OEM level, and perhaps even slightly lower at high piston velocities -- which would be just about heaven on my car, on my roads, as the upward kick is my main obstacle to good ride comfort.
(Note: the kick is why I'm still on 15" "Grand Touring" tires at 27psi -- the tires play an enormous role in reducing the initial impacts.)
That being said, it's not clear if reduced compression damping will do the trick for Peter (in San Francisco), and it's quite possible that the KYB is the best solution for him. We'll hit that in the next post.
- C


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## Ceilidh (Jan 7, 2004)

*Re: Why there is a hope..... (pyce)*


_Quote, originally posted by *pyce* »_
.......perhaps the more popular damper makers here (Bilstein, Koni, etc) have not really addressed specifically certain needs and have gone flat out in favoring performance first and the rest is “if you can not take it – do not buy it” thing. Perhaps that “red surrounded” text in the link also explains why some us have particular issues with German aftermarket dampers on our specific roads that are very far from what an Autobahn is (in terms of quality). So, if Bilstein and Koni do have the same part numbers for their internal (German) market and for our NA market – then perhaps we can be quiet sure they have “tuned” that stuff to suit them first, which automatically means that it may not suit few of us, like in the given example in the link of German cars doing not particularly well on British roads.


(Peter, thank you very much for getting the first overlay graph up so quickly! I realize how swamped you are, and I really appreciate your helping out (especially given my own frequent and lengthy absences from the forum!).)
Ok Folks,
Now a few words about Peter's comments above (Peter, if I misrepresent or misstate you at any point, do please chime in!):
There are two main issues at work here: one is the strength of the damping; the other is the shape of the damping curve. We'll hit them in sequence:
1) On the damping side of things, the Bilsteins are simply very stiff (even the TC's are about 50% stiffer than stock, and the as-yet-untested HD's and Sports are supposed to be much, much stiffer still. That's great for performance, but it leads to a pretty stiff ride.
For the Konis, the question is why is the compression so high? The answer presumably lies in the 2:1 adjustability range built into the rebound. Because the Koni compression setting is fixed (non-adjustable), it has to be high enough so as to be actually usable in the situations where the highest rebound rates are needed. Because of that, the compression is far higher than it needs to be when used with the rebound's near full-soft.
The problem for those of us on rough roads is that, when mated to OEM or near-OEM-rate springs, the Konis are meant to be used near full-soft -- even the folks on SofSports (if they care at all about ride comfort) don't seem to go above ~50%, and I (on stock springs) am at ~12-13% (there's roughly 2 turns of adjustment, so 1/4 turn = 12.5% of the full range). On roads with sharp upward impacts (which we get on occasion in the area where I drive), the Koni Yellow compression is simply too high -- that's why the OEM, KYB, and Bilstein TC compression rates are all basically 1/2 - 3/5 of the Koni level.
(Note: passenger car (as opposed to competition car) shocks typically have a rebound:compression ratio somewhere between 2:1 and 3:1 -- and that's what we see in the OEM, KYB, and TC shocks (and presumably what we would see in the Koni at around 50% stiffness); the soft compression takes care of the impacts, and the stiffer rebound controls the chassis motions....)
And finally, why is there a 2:1 adjustment ratio? It's presumably there so that we can dial up the damping for max handling on stiff aftermarket springs (note: when I had Shine front springs, the Konis felt best at 88% stiffness).
So that's part of what Peter means about the Germans making max performance stuff that might not be best suited for our needs on our roads: in the case of the Bilsteins, the shocks are simply very stiff; in the case of the Konis, the Yellows have a rebound range that's stretched very high to accommodate high-performance needs, and that requires a compression rate that's too high for comfort on rough roads.
.
2) The other point (which is more directly what Peter was referring to) has to do with the precise shape of the damping curves. And for this discussion, we might best wait for the velocity-vs-force diagrams to come out (it's possible to see the relationships in the displacement - force plots that have been posted so far, but the interpretation is a little tricky: on the displacement - force plots, a linear force-velocity relationship ends up looking like a sinusoid, not a straight line....).
But to give everyone a preview: if your roads are fairly smooth and you only have isolated bumps to deal with (I suppose even a German road might have a pothole every now and then







), and if your goal is excellent high-speed handling on the Autobahn, then your general damping approach will be to have lots of low-piston-velocity damping to control the chassis motions (i.e., to damp out roll, float, pitch, etc.), but relatively low rates at the high piston-velocities that occur on bumps. This is the standard "damping curve" we're all taught to shoot for, and it gives you a noticeable kink in a velocity-force plot, and a sort of "square-cornered" profile in a displacement-force graph (on Peter's most recent post, you can see the squareness really clearly in the OEM rebound curve (the blue line)); it also gives you a fairly steep initial line in both kinds of plots (you can see that steepness in the TC rebound line). This kind of damping gives you the fabled German ride: absolutely unflustered chassis motions, and a firm but controlled ride over the bumps.
The problem, however, is what happens when you use this kind of shock absorber not on a road that's a flat surface with occasional bumps, but instead one where the entire road surface is kind of wavy. On that kind of road, the "bumps" don't cause a rapid bounce of the wheels; instead, the waves smoothly pick up and drop down the wheels at relatively slow speeds -- the very speeds that your damping firmly for reasons of chassis control. Here, the German damping philosophy will get you into trouble -- instead of having a smooth-riding car, you have one that's doggedly trying to follow all the waves in the road.
In the text Peter's referring to, the writer's English, and I can picture exactly the sort of road the writer is thinking of: for example, if you drive over the Fens of East Anglia, east of London, you can find yourself on narrow, dead straight, dead level roads that are built on top of old Roman roads -- but where the really, really solid Roman foundations have had a couple of millenia to sink unevenly into the soft marshy ground. The end result is something that feels (and believe it or not, I'm not exaggerating) like riding in a high speed catamaran in a crowded harbour with random wakes from all the other boats -- there are literally random, smooth waves in the road going in every direction, so that each of the car's 4 wheels are independently going up and down - very smoothly, but very far - at totally random times. A good English car (heck, even a bad English car -- I was in a '72 Spitfire!) will cruise straight over the waves, with the wheels going crazy underneath and even the steering wheel rocking randomly back and forth (you just relax your grip on the wheel, let it rock, and car keeps going straight); a good German car, however (this time, in a Fiesta) will try to stay glued to each wave, and your head (and body) gets tossed all over the place.
How does the English car track straight over these bizarre roads? The good ones have incredibly subtle geometric control over wheel camber, toe, track, etc. even with big wheel deflections (yes, I'm actually saying something nice about English cars here -- but this is an area where they really excel).....and they use much softer damping at low-piston velocities than do their German counterparts.
(By the way, is f1forkvr6 (Chris) reading along? If so, Chris will likely appreciate this -- cars used to have much more distinct national characters, in part because they were so optimized for local conditions. It's a little sad now that we've all become so global and sophisticated; the differences are still there, but they're just a shadow of what they used to be!







)
Anyway, a current area we're looking at concerns why the KYB's feel so comfortable on Peter's car. We'll hit that when we have the velocity-force graphs, but it's interesting that they appear to have a very "American" damping curve: less low-velocity damping than even the British use, a very smooth and straight velocity profile (hard to see on the current graphs), and relatively firm high-velocity damping. It's also interesting (and this is a recent realization) that Peter's roads are not Germanic smooth-concrete-with-isolated-craters, but rather very wavy concrete with massive holes and ridges -- but with the waves recurring at fixed periodic intervals. This is exactly the type of road that gives rise to something called "Freeway Hop" (sometimes called "L.A. Freeway Hop", and it's a distinctly American phenomenon that drives European suspension tuners crazy (it's a primary reason why OEM cars drive differently here than they do in Europe).
Anyway, the jury's out on just what's going on with Peter's car on Peter's roads (there are a lot of things we're pondering about), but there's at least the possibility that we ("we" meaning all of us, collectively, on the forum) might wind up recommending different shocks for different regions of the country....
More later -- Happy Thanksgiving everyone!
- Ceilidh


_Modified by Ceilidh at 11:32 AM 11-24-2004_


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## Ceilidh (Jan 7, 2004)

*Re: Winston - Cadenza_7o (pyce)*


_Quote, originally posted by *pyce* »_....For the second part I have to go to the shop again and construct the graphs.....I learnt the basic on that software, so he let me go and do these things on my own now.....I can actually "clean" them (the software has this capability) and show the requested from you Force vs. Velocity with only rebound or only compression (and of course both if needed) so the graphs are cleaner, with less lines and easier to read. I will go there again tomorrow to do so....


Peter, thanks very very much again! Don't knock yourself out -- I of course eagerly await the graphs, but please do take your time.








As for "cleaning it up", we might not want to do that: I'd expect the software is set up to generate a clean "steady-state" graphs (meaning, it tries to show what the damping force is for a steady pull or push at a fixed velocity), and thus will try to get rid of all the "noise" resulting from transient behaviour. The problem of course, is that we want to know the transient behaviour! (Especially how the shock reacts at the opening phase of a bump....)
Thus, if it's not too much trouble, could you please try (in addition to the "clean" graph) one graph at 18.0 in/sec? If it comes out looking like the cleaned up graph (which I presume is made by drawing an "envelope" around the data from all the different-speed runs), then there's no issue. But if it looks very different, it might be nice to have the 18.0 in/sec (or any representative high-v run) plot as well, so we can look at transient behaviour.
Thanks again, and do take your time -- there's no hurry at all!








- W


_Modified by Ceilidh at 12:30 PM 11-24-2004_


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## pyce (Nov 7, 2001)

*OEM - TC - KYB - Koni - 18.00 in/sec - F vs. V*

Winston.... when I said "to clean" the graphs, I did not mean to "manipulate" it, eliminating the rough sectors.... I guess I got confused when reading your request. You asked for the upper left and lower right part of the Force vs. Displacement and then asked for the Force vs. Velocity, so my understanding was that the second graph (the F vs. V) should also show ONLY the corresponded from the top left and bottom right and because the software does not do that, I thought I had to "clean" (delete) the rest of the lines from the other two sectors, so to make it easier to read. I am still not sure whether this is what you need







Sorry, not enough coffee this morning..... Anyway, here is what I got so far - it is not elaborated graph with the OEM - TS Sport - Koni Yellow Soft - KYB AGX Soft on the 18.00 in/sec - Force vs. Absolute Velocity. Let me know if you want me to view only the lines that correspond to the top left and bottom right...








On another note - you are talking about low speed and "copy the road" situations..... so, I went digging the old graphs (where we had all dampers together) and found out the 4.00 and 6.00 in/sec scenarios - it is amazing how the TC sport has more than double the rebound compare to the rest!







I got (finally) the accelerometer's graphs as well, but for not confusing the issue, I would let you finish your posting on the graph posted here and then will post all the stuff I am talking about.... Thanks again for doing all this deep explanations for all of us!


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## Ceilidh (Jan 7, 2004)

*Re: OEM - TC - KYB - Koni - 18.00 in/sec - F vs. V (pyce)*

Hi Peter!
My mistake -- I misinterpreted what you meant by "clean"! (A long time ago you showed by an F vs. V plot that had all the data from all the different runs (18.0, 16.0, 14.0, 12.0 in/sec, etc.) thrown together, and it was utterly confusing -- when you mentioned software, I assumed it was one that would draw an envelope around all that data, thus producing a quasi-steady state diagram....)
Anyway, your original interpretation was correct -- having just the upper left and lower right velocities and forces would be ideal. (Only, it's a pain that the curves don't pass through (0,0)....). Hmmm. If it your other runs has the curve crossing the 0,0 point (maybe one of the lower velocity runs), maybe we'll have to take the low-vel data from that run and splice it to the high-vel part of the 18.0 run. Gosh that'll be a pain! ......Let's just see how a clean 18.0 and (if it's handy) 6.0 graph looks -- thanks!!
P.S. -- if the curves don't pass through 0,0 then maybe for clarity's sake it might be good to show the rebound and compression separately, on two separate plots..... (?)
Thanks again, Peter!
- W


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## pyce (Nov 7, 2001)

*Re: OEM - TC - KYB - Koni - 18.00 in/sec - F vs. V (Ceilidh)*

Winston - unfortunately (for visualizing) they never go through the 0,0 point at the end of the compression stroke and beginning of the rebound, so this was precisely why I was thinking to "clean" the pictures and make them show the lines you requested, plus, to "line up" the graphs to start at 0,0 for the beginning of the rebound on a separate graph perhaps..... Let me see what can I do and how valid is going to be. As for the lower speeds, it is the same "mess" so it is really not going to help us much if we lower the speeds..... Hope I can crank this in few minutes.


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## pyce (Nov 7, 2001)

*Re: OEM - TC - KYB - Koni - 18.00 in/sec - F vs. V (pyce)*

Ok, this is the best I can do given the time..... Just a short explanation of what was done - traced the graphs we have with simple 3 degree curves from another package, then non-proportionally (vertically) scaled the curves so they all start at the same point (0,0), maintaining the shapes and the end points (values) as original. We now have the following picture that represents the Beginning Only of the Compression (the top left from the displacement graphs) and Beginning Only of Rebound (the bottom right from the displacement graphs). The scaling does modify little bit the shapes of the curves in the Beginning, but this is the most accurate we can go anyway. Hope this helps..... I will try to do few for the lower speeds, as there is really where we (perhaps) should be more interested. Winston, let me know if this works for you


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## Ceilidh (Jan 7, 2004)

*Re: OEM - TC - KYB - Koni - 18.00 in/sec - F vs. V (pyce)*

Hi Peter,
This is great!! Just so I understand: you used some sort of 3rd order spline or curve-fitting package to connect the dots, kept the high velocity endpoints fixed, but for each shock you applied a different proportionality & origin shift to get things to line up at 0,0, correct? And if so, then shapes are more or less retained, as are low-velocity deviations from initial starting force, but the absolute values of the low-velocity forces are *not* retained, correct?
Assuming even part of the above is right, may I please ask you







for just one more pre-Thanksgiving figure, in addition to whatever else you're already thinking of doing? It'd be nice to have exactly what you've already done -- same data, same curve-fitting, same colours, only this time leave out the proportional scaling, and just have the raw data (with curve-fitting). I know that the compression and rebound won't converge at a single vertex, but we'll still be able to interpret some things from it --- thank you very, very much again; this is fabulous work!!
- W


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## pyce (Nov 7, 2001)

*Re: OEM - TC - KYB - Koni - 18.00 in/sec - F vs. V (Ceilidh)*

I knew you were going to ask to leave it as it was







so I did another one while you were typing this..... here it is:


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## Ceilidh (Jan 7, 2004)

*Re: OEM - TC - KYB - Koni - 18.00 in/sec - F vs. V (pyce)*

Wow, scary -- you're becoming a mind reader!








Peter,
On the basis of this graph (i.e., perhaps the other velocity runs look different....) it appears that:
1) It's easy to see (for a variety of reasons) why the TC's were so uncomfortable;
2) Your dyno-man Phil meant exactly what he seemed to be saying -- there's a lot of hysteresis both in the Koni and in the TC, but they're in opposite senses; with the TC, the continuously-bad road is going to feel much worse than a few isolated bumps. The Konis go the opposite way -- on a continuous series of bumps, they'll feel better than they do on isolated bumps (which is how my car feels on the badly-broken Boston pavement -- it seems to float across, whereas more isolated bumps cause crashing.
3) The KYB's are starting to make sense.....
4) There's still hope for the Koni Reds....
5) I can see why Carroll Smith said that shocks are confusing....
Explanations and analyses in the next couple of days (gotta spend time with the folks now!!). Thanks again for the great graphs -- this is pretty neat!
- W


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## pyce (Nov 7, 2001)

*Re: OEM - TC - KYB - Koni - 4.00 in/sec*

... While enjoying the turkey, check this one out! The low speed (4.00 in/sec) rebound of the TC Sport precisely! ..... It has double the KYB rebound and more than triple the OE and Koni on Soft rebound!!! Talking about Touring, LOL








Happy Thanksgiving to whoever celebrates it!


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## pyce (Nov 7, 2001)

*Non-Proportional Scaling....*

Wanted to put some light on this Non-Proportional Scaling we were talking before…
Here is a graph (used a curve similar to the OE rebound curve) that shows what exactly happens when a 3 degree curve is non-proportionally scaled (vertical scale on “y” axis in this case):








Basically, what we have is one curve that goes from point A to point B1. The pivot point goes at point A, which means while the scaling goes that point A is not going to move and will be the “zero” in this case. That point A from our graphs was corresponding to the max. value of Force for each curve, and therefore we scale around that point, this way the position of the point itself to remain unchanged on the graph. So, the vertical (axis Y) scaling is interactively applied and the line starts “compressing” down, going through points B2, B3 to end to a point B4, which in this case is let’s say where we want it to end. This is basically what was done as to start all lines form the (0,0) point. Yes, the curve is no longer the same, but it maintains the proportions of it’s shape. Note the A1, A2, A3 and A4 points (casual point on the line) and the relation to the B1, B2, B3 and B4 points – the ratio (proportion) among the A’s and the B’s is the same, even if the values are different – so we have a non-proportional vertical scaling.


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## Ceilidh (Jan 7, 2004)

*Re: OEM - TC - KYB - Koni - 18.00 in/sec - F vs. V (pyce)*

Hello Folks,
Peter has a number of accelerometer plots to show off after the initial shock analysis is done, so I (Ceilidh) have become the bottleneck.







Hence, let's dive into the graphs!
1) First off, for Peter: Still looking forward to seeing the Koni Reds, but a little browsing on the Koni website was unsettling: according to their "generic" diagram:
http://www.koni.com/_cars/_gen....html
there's not a whole of lot of Compression difference between the Red and Yellow. If the VW Reds turn out to be as close to Yellow in Compression stiffness as the shocks in the above graph, then we might not get the comfort improvement I was hoping for.....
2) Next, the caveats: everybody, this is an analysis-in-progress, and we're trying to figure these things out. (In other words, we might later decide that what we say here in wrong!) Also, we're going from the 18.0 in/sec graphs here, and there are indications that this graph minimizes the low-velocity damping curve; we might have to revise things when we see graps from other runs.
(Along these lines, Peter, could you (someday) show a Force-Velocity plot of the Koni Yellows (full-soft) alone, again upper-left and lower-right quadrants, but this time with all the velocity runs (2.00 in/sec, 4.00 in/sec...........30 in/sec) all plotted together?)
3) Ok, enough hedging.







We'll start with Peter's "cleaned up" (rotated) graph:








This graph more or less preserves shapes, and puts all the shocks on a common origin (0,0) for comparison. First look at the compression curve (lines above the horizontal X-axis):
A) The OEM shock (black curve) shows a classic American profile: it's almost a straight line, slanting up from 0,0 and providing damping force at a rate almost proportional to piston velocity.
B) In contrast, the KYB and TC shocks (Red and Blue) have a more "German" profile (the TC somewhat more than the KYB): both shocks are more "rounded" near the 0,0 origin, and thus provide more compression damping at low-piston velocities than does the OEM shock, while keeping the high-piston velocities in check (in fact, the TC is almost down to OEM levels at the highest velocities).
C) All three shocks (OEM, KYB, TC) have very similar high-velocity damping rates, and should feel roughly similar on sharp bumps (at least in the initial compression "kick").
D) At low piston speeds, however, the stronger KYB and TC curves (if these curves are repeated for the front shocks) should yield more positive turn-in on corner entry, a little better control of brake dive, and a somewhat busier feel on wavy roads...
E) The Koni (Yellow line), however, has a radically different shape and path. We'll ignore the shape for now, in part because I've a feeling the lower-velocity runs will look different, and in part because it's better-discussed in the next graph -- but let's look at the high-velocity curve. Simply put, it's huge! - almost twice as great as OEM, and much much higher than TC or KYB. This is (for my car) the near-objectional part of the KONI ride: the very stiff compressional damping means that sharp jolts (which cause high upward piston velocities) are transmitted right into the chassis, whereas the softer OEM/KYB/TC damping allows the wheels to rise and absorb more of the shock. The flip side is that initial turn in will likely be helped, and I definitely don't need to worry about the unsprung weight getting out of control....








NEXT, we'll turn to the Rebound:
F) Here's a surprise! The KYB is the "American" curve -- soft initial damping so the wheels are free to go up and down even on the uneven concrete of Peter's S.F. freeways (thus avoiding the dreaded "Freeway Hop"), a very straight, linear "gain" with velocity so there are no "jerks" (periods of high rate-of-change-of-acceleration) in a big up-down wheel cycle (again, the sort of cycle that gets excited by high speed travel on uneven, wavy concrete), and relatively firm high-speed damping to give the perception (the illusion?) of "sportiness" via increased firmness on little bumps. On the basis of this curve, we'd expect the KYB to feel sporty and fairly comfortable on the freeways, but the absolute roadholding (because of the high velocity damping) might actually decline a little.
G) What's the OEM curve doing? It's got really soft low-velocity damping: float, dive, and roll are going to be an issue, but the wheels have an even better shot at absorbing the ups and downs of the concrete freeways. In fact, the "nose" of the curve is extremely sharp: there's not very much damping at all at the lowest speeds, and that means that when you're on a smooth road, the wheels are free to follow all the inevitable, gradual little invisible dips and hollows, and the car will seem to waft serenely over the highway. How about the high-velocity damping? That's quite low too, which doesn't do much for the perception of sportiness, but it'll will enhance roadholding (the wheels are free to follow the fast-paced little bumps). So the car's capable of going quite fast -- but it won't feel like it's going fast, at least not in terms of the ride sensations -- and it's best suited to someone with a "smooth" driving style. Darters will be unhappy with this shock, however, since (if given sudden "jagged" control inputs) it'll roll, heave, and pitch like a drunken sailor.....
But hey, what's up with the medium-velocity damping -- why's there a (downwards) bump? This is kind of interesting. It looks like like the OEM engineers have minimized the low-velocity damping as much as they can to improve the ride, but things are now too uncontrolled (even by OEM standards!) -- hence they've "bumped" the medium-velocity damping to control the worst lurching. i.e., the car will lurch around and feel soggy, but the lurching never gets totally out of control, because if the lurching gets really fast, the "bump" part of the curve comes into play and vigorously slows down the motion. Comfort-wise this bump is supposed to cause jerking problems (according to the textbooks)....but the engineers have earned their pay here, as in practice things are actually fine.
Bottom-line: the OEM curve goes for serenity, good roadholding on broken pavement, but a (relatively) soggy feel and indifferent chassis control in transitions. If you drive smoothly on awful roads, this might be the best shock. If your fondness is for lightning high speed lane changes and you treat the throttle and brake as On/Off switches (i.e., if you're a "Darter"







), you're going to absolutely hate it.
H) The TC? Hail to the Fatherland!! Here's the classic German profile -- a lot of low-speed rebound control to keep the chassis in check, and a pronounced bend-off at higher piston speeds so that damping on the fast bumps doesn't go through the roof. Chassis control should be pretty good -- this is a car that should respond well to steering and brake inputs (i.e., it'll handle well) -- but the damping is rather high on the chatter bumps, so rough-road roadholding goes down, and the extremely firm body control at low piston speeds mean it's going to follow every subtle wave in the road. On an English country lane this shock might cause "head toss"; on Peter's S.F. freeways it'll pitch the car forward and back on every slab of concrete, and at certain speeds (near harmonic resonance) the ride might be just awful. But on Boston roads, this might be ok....
I) Koni? Another surprise! From Peter's raves about the KYB, I thought the Koni would be more like the TC, but at Full-Soft it's really quite similar to the KYB: almost identical damping at the low-piston-velocities that govern handling, with less high-speed damping and hence better roadholding on the fast chatter bumps (though it might be less "sporty-feeling"); plus the rolloff is done so gradually it's hard to see how jerking can be a problem. Not a bad curve - though it'd be interesting to see if the curve becomes more "German" at stiffer settings.... Anyway, overall damping levels are very low -- even lower than OEM in places -- and thus it's not going to feel a whole lot better than OEM in the fast transitions; this is a nice classical curve, but it's really, really soft (presumably to claw back a little of the comfort lost to the stiff compression curve).
J) Summary: from the curves, we'd expect the TC to give the best transient handling but the most annoying tendency to follow every wave in the road (and it has the potential to be horrible on wavy concrete freeways); the OEM will be surprisingly fast when driven smoothly against the stopwatch, but it won't feel "sporty" and the darters will be cursing the roll, pitch, and heave; the Konis (at full-soft) will be almost underdamped in fast maneuvers but turn-in should be not bad -- but on true sharp ridges, the impacts will come crashing through; and the KYBs should feel fairly similar to stock, only "sportier" with better handling, a moderately firmer ride and more of the sensations of speed (though some of that sportiness will be an illusion -- the actual roadholding on rough pavement should be worse than stock).
.
4) Now for the RAW DATA (i.e., the previous graph was "cleaned up" so that we could focus on the shapes of the curve; now we'll look at the actual damping forces that occurred on the 18.0 in/sec dyno runs):








Weird, eh? This plot is again at 18.0 in/sec (meaning the test dyno hit a maximum speed of 18.0 in/sec at each stroke), and the curves don't meet at 0,0 -- meeting at 0,0 means the shocks don't exert any damping forces when they're not moving (which makes intuitive sense), but here the curves suggest there are shock forces even when the shock is sitting still. Such behaviour is an example of hysteresis, and it has implications for how these shocks will feel on a prolonged stretch of badly broken pavement:
A) We start with KYB and OEM (black and red): both shocks fail to hit the origin, but they're really close -- close enough that we needn't worry too much about it (it's likely a bit of "stiction" -- the shocks having a little sticky friction from the various hydraulic seals etc. on the shafts...). These shocks should feel consistent regardless of how closely spaced the bumps are.
B) But look at the TC: in rebound (lower blue curve), the damping force at zero-velocity is bigger (more negative) than the whole initial nose of the OEM curve. To see what this means, consider what happens when the wheel hits a bump: at first, the wheels rise, which compresses the spring & shock; when it reaches its highest point, it reverses direction and begins to move downward (which extends the spring & shock). With the OEM shock, the downward "return" motion is initially unchecked -- the damper lets the spring push the wheel back down onto the pavement, which is good for both ride and roadholding: the chassis can keep riding level, and there's good contact between tire and road. But with the TC, the shock is really "fighting" the spring: at the high point of the wheel's travel, the shock is actually sucking the wheel upward(!), and the only way for the wheel to come down rapidly is for the whole chassis to come down with it. From the ride perspective, what it should feel like (Peter, can you confirm or refute this?) is a sudden "check" in the upward motion -- the initial bump motion might be ok, but near the top of the bump the motion suddenly stops and the car feels like it jerks downward. (This is the opposite to what we'd expect with the Konis, which should simply crash upwards on a sharp bump, but with a well-controlled aftermath...)
Now, from some of the earlier graphs that Peter's posted, this feature of the TC appears to be a dynamic process -- it's not one that shows up on isolated bumps, but instead comes about when the shock is being rapidly cycled up and down. It's consistent with what Phil (the shock dyno guy) first told Peter: it seems almost as if valves are opening inside the TC and allowing fluid to shoot through with considerable velocity, and the inertia of that flow continues to draw fluid out of the chambers long after they should ideally have stopped. The upshot is that a long stretch of broken pavement should feel terrible on these TC's -- the wheels, instead of pattering away beneath an unflustered chassis, will seem to be yanking the chassis down (and sometimes up) at seemingly random intervals, depending upon how they happened to respond to the previous bumps.
C) Now look at the KONIs -- weird!!! The compression curve doesn't have a significant offset (though I think the sharp initial "nose" is another hysteresis effect....), but the Rebound curve is not only offset a huge amount, but the offset is opposite to that of the TC!!
Once again, the left end of the Rebound curve (the yellow line that sweeps downward, left to right) shows the force exerted by the damper at the moment when the wheel has stopped bumping upwards, and is just starting to head back down. The curious thing is that the curve starts in the "positive" region -- it's trying to extend itself at zero piston-velocity. What does this mean?
Consider again what happens after the wheel & tire have crested a bump, and are starting to travel downwards. In the "ideal" case the shock just lets wheel go (so it can follow the road without jerking the chassis downwards) -- and here the shock goes one better than "ideal", by actually pushing the wheel downwards towards the road! (Note: this behaviour is precisely one of the goals of an electronically-controlled "active suspension"....) It appears that the shock is in effect pressurizing during rapid compression, and this buildup of pressure serves to launch the wheel back downwards once the bump passes. From a roadholding perspective, this action keeps the wheel pressed against even broken pavement, which enhances roadholding; from the ride perspective, you don't get a "jerk" at the top of a bump -- instead, the car feels like it "floats" off the back of the bump.
Or in other words, on a long stretch of continuous bad pavement, the shock feels better than it does on an isolated bump.
Note: this is the one shock behaviour that I (Ceilidh) can actually verify (I've never tried a KYB or TC, but I have Koni Yellows on my car): sharp upward impacts are always bad, and isolated bumps can make me cringe, but when I hit some of the really awful roads in the Boston area -- the ones that appear to have been patched by drunken contractors every 5th year since The Revolution, and never once resurfaced -- the ride magically levels off after the initial impact, and passengers have commented with surprise on how smooth everything feels. (But then we hit more widely spaced expansion joints on the highway, and the jolts come crashing through....)
.
Anyway, that's the view from the theorist's seat.







Looking forward to Peter's next findings!
- Ceilidh
P.S. -- Out of the current shocks, the KYB looks the best; but if the Koni's had a compression curve that was simply 60% of what it currently is (and if the Koni rebound curve doesn't change shape too much with adjustment), then that might be the best way to go.
P.P.S. -- Peter, can you (someday) post up the KYB full-stiff as well? I'm interested in how they (as you report) increase handling without decreasing ride comfort -- thanks!



_Modified by Ceilidh at 10:15 AM 11-27-2004_


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## Ceilidh (Jan 7, 2004)

*Re: OEM - TC - KYB - Koni - 18.00 in/sec - F vs. V (Ceilidh)*

Thanks for the posting-images advice, Peter -- I've followed your edits, and the pictures should show up with the post; hopefully it'll be easier to follow now!
- C (W)


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## pyce (Nov 7, 2001)

*KYB soft vs KYB stiff - accelerometer grpahs...*

Excellent explanation, Winston! I wish we have done this “Dampers” thread much earlier and before the long-winded “Shine/Koni/Bilstein” thread. There is so much we can achieve with the dampers, but it somehow had been overlooked for very long time, with majority concentrating on the springs by themselves. Thank you very much for the time spent. I deeply appreciate it. I hope folks would find time to not only read your posts, but to try to understand the analysis you gave and hopefully to make a more educated choice of a damper that would best fit their desire and fit their application. Only one note I wish to make:

_Quote, originally posted by *Ceilidh* »_ .....P.S. -- Out of the current shocks, the KYB looks the best; but if the Koni's had a compression curve that was simply 60% of what it currently is (and if the Koni rebound curve doesn't change shape too much with adjustment), then that might be the best way to go.

We both know (and those few who follow here) that when you said “KYB looks the best” you mean a specific compromise that favors comfort first, with some added roll control (if I may say so) that give the “sporty” feel. I just would like to point this out for guys who are not following, but may spot your sentence and then leave this place with the wrong idea that “KYB is the best” period! It is not. None of them is “The Best” because they all (apparently) are “designed” with different purposes in mind, favor one thing over the other, etc. It would be safer to say that the “KYB so far look the best on paper and some modest tests - if Sport*y* feel and some comfort is the goal”. Just wanted to make sure someone does not read it differently, because there are folks that see the long post and really do not have time, neither desire, to go through, but curious enough to know what is going on, so it is natural to jump briefly to the last few lines where usually the authors give the wrap-up, and then that “P.S:” , standing alone there, may mislead.










_Quote, originally posted by *Ceilidh* »_ P.P.S. -- …. can you (someday) post up the KYB full-stiff as well? I'm interested in how they (as you report) increase handling without decreasing ride comfort -- thanks! .....

All that will happen next week, when the Koni Red and Bilstein HD (and apparently I found a “Sport” too!) arrive. I will go there and will bring all the graphs you requested….
Meanwhile, here are two Accelerometer graphs from the KYB and as you will read on the graphs, one is on full soft and one is on full stiff. Now, we already have the dynos and we know that there is little difference between full soft and stiff, so it is expected to have also little difference in ride quality. But the striking fact is that the difference in ride is very minimal, meanwhile the difference in “stiffening” the chassis in transitions is quiet more than that. I mean, if someone rides in the car on full soft and full stiff, will evaluate the “lost in comfort” when going towards stiff as let’s say 10-20%, but then if that someone is given the car to go do a slalom in a parking lot – he would think the difference between soft and stiff is more like 30-40%. Do not get these numbers are absolute. I would hate to see someone posting tomorrow that KYB rides 10% stiffer than stock and handles 40% better than stock – I am just using them as to express some feeling from a test drive, that is it. So, while can’t really come out with data to prove the “handling” difference, here we have the accelerometer graphs to prove at least the comfort difference:
















As you can see – not identical, but really close. As we have shown earlier on this thread, you can get this difference by simply putting slightly more pressure in the tires! There are even some spikes that are better controlled by the damper at full stiff (and it feels that way) than on full soft. Overall, not bad “sporty” damper for the given comfort. Looking forward for the Red’s, which is my last hope for pure OE replacement. That would be out “Plan A”. If the Koni Red fails to deliver the OE curves on any of it’s settings – then we go to “Plan B” which is to rebuild the Koni Yellow to OE specs on their softest setting, put some external knobs on the rears, so to get easier adjustability in case the car feels “sporty” on a weekend – and live like this for the rest of the car’s life, or damper’s life – whichever comes first


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## Ceilidh (Jan 7, 2004)

*Re: KYB soft vs KYB stiff - accelerometer grpahs... (pyce)*


_Quote, originally posted by *pyce* »_We both know (and those few who follow here) that when you said “KYB looks the best” you mean a specific compromise that favors comfort first, with some added roll control (if I may say so) that give the “sporty” feel. I just would like to point this out for guys who are not following, but may spot your sentence and then leave this place with the wrong idea that “KYB is the best” period! It is not. None of them is “The Best” because they all (apparently) are “designed” with different purposes in mind, favor one thing over the other, etc. 

Thanks Peter, you're absolutely right! That statement was misleading!
What I was thinking when I wrote that was that the KYB looks best for someone who drives on concrete freeways (the uneven sort that can induce freeway hop) and who wants something with more chassis control than stock, and more of a "sporty feel" without a huge ride penalty....
The TC's, as the most Germanic, look like they'll be ideal for someone who drives in Germanic conditions: smooth roads with an occasional small bump or pothole; high speeds; and the desire for better chassis control and transitional handling.
OEM & Koni are as described earlier -- this is all definitely Different Horses for Different Courses, and you're absolutely right: there's no one "Best" that's best for everybody!
- C


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## pyce (Nov 7, 2001)

*GTI-Neuspeed-Koni vs. R32*

Here is an attempt to break the accelerometer








Car is a Golf GTI 1.8T with Neuspeed Sport springs and Koni Yellow set at about 50% (at least the rears, the fronts if I remember correctly were on 75% stiff). The car is on 18” wheels with the related 225-40-18 rubber…… As you can see, the ride in between the spikes is not as “busy” and uncomfortable as one would expect. Perhaps the Bilstein TC on 15” wheels and stock spring do actually cause more jarring and un-comfort than this combo! But where this really looks bad is the single bigger bumps situation. Where you see the green and red dots on the top and bottom border, those are spikes that go to +14 and -14 (!) – the highest we ever recorded. They cold have been shown on the graph, but this meant to make the picture in a different scale, so not easy to compare with the rest. As you may note, we are trying to use graphs with all same vertical max values of +7 and -9, so to be easier to put them next to each other and see clearer the difference. This whole spike issue may be as well the car sitting on its buffers, so at those precise moments there is no more suspension left to absorb anything, therefore the very high numbers. Here is for you all to admire:








To compare to the above, here we have another Golf two doors, on 18” wheels with 225-40-18, this time set at 40 PSI all around – it is a R32 thought! Everything stock except a rear anti-roll bar (can’t remember whether 21 or 22 mm, but remember it was H&R). Look at the much better (comfort wise) graphs. The rebound never even reaches the -5 m/s value! The compression never gets to +7 m/s! A stock Beetle with 16” wheels and same tire pressure (touring tires too!) offers much higher spikes and “busier” ride too. I guess we have a pretty good “visual proof” of what VW has done with the R32’s rear suspension….


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## alexb75 (Dec 29, 2002)

*Re: GTI-Neuspeed-Koni vs. R32 (pyce)*

The Koni car was very stiff. I barely can stand 50% rear, and the stiffest rear setting with acceptable comfort is 37% (3/4 turn). 
But the accelometer shows what I always feel, Koni on smaller bumps is nice riding, but oh boy, do u feel those big ones! 
How's Bilstein test coming?


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## pyce (Nov 7, 2001)

*Re: GTI-Neuspeed-Koni vs. R32 (alexb75)*

The Bilstein should be here today, so perhaps will be on the dyno tomorrow...... if you all wish to have some fun - bets are open!







Let's see who wold guess it right where the HD will stand against the dampers we tested so far


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## alexb75 (Dec 29, 2002)

*Re: GTI-Neuspeed-Koni vs. R32 (pyce)*


_Quote, originally posted by *pyce* »_The Bilstein should be here today, so perhaps will be on the dyno tomorrow...... if you all wish to have some fun - bets are open!







Let's see who wold guess it right where the HD will stand against the dampers we tested so far

















Here's what I think: Less compression than Koni, way more rebound than softest, but less than stiffest Koni.
On the same stretch of road, it will have more ups/downs on accelometer than Koni... will be similar at big bumps as the Koni 50% just posted...
Let's see how wrong I am


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## Ceilidh (Jan 7, 2004)

*Re: GTI-Neuspeed-Koni vs. R32 (pyce)*


_Quote, originally posted by *pyce* »_Here is an attempt to break the accelerometer








Car is a Golf GTI 1.8T with Neuspeed Sport springs and Koni Yellow set at about 50% (at least the rears, the fronts if I remember correctly were on 75% stiff).........Where you see the green and red dots on the top and bottom border, those are spikes that go to +14 and -14 (!) – the highest we ever recorded.......

Fun graphs!








Just a little reminder for everyone: 1 g = 9.8 m/s^2, so those peaks are past 1.5 g's !


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## BAMA TDI (Nov 26, 2002)

I am reading this thread with great interest. I have an A4 2000 Jetta GLS TDI with 102,000 some odd miles on it. It's getting time to considering replacing the shocks/struts. I got a good deal on some A4 Sport Springs off an A4 Jetta 1.8T on e-bay. I don't want to lower the car. I do want it to have a slightly more firm ride and better handling but I am not looking for autocross type handling or ride by any means. When I say better handling, I am referring mostly to body lean in a curve. There are some entrance ramps to the I-state system around here that have reverse camber. (I think that's the correct term) Car is starting to lean more than when it was new. I have been flipping a coin between Bilstein HDs or TCs. I will continue to keep up with this thread.
pyce, and eveyrone else, keep up the good work!!!
Regards,
John


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## pyce (Nov 7, 2001)

*Koni Rosso are here ....*

Well, the HD did not arrive last night, but the Koni Red did – so, at least we have something to dyno today








I would like to thank very much Marco (aka “thinkman”) who sent the Konis all the way from Italy! http://****************.com/smile/emthup.gif http://****************.com/smile/emgift.gif Tried very hard to get them here, but the company that sells the Vogtland Kit (lowering springs with Koni Red) would not sell just the dampers (they said it is Koni N.A. decision!). Then I hear they are sold in Canada, but somehow no one could help me to locate them (different people tried and no luck, so perhaps, I do not know how available they are in Canada?). So, we had to get them from Europe. Thanks again, Marco! This damper was the biggest so far pain to get in, and I sure hope it is worth the effort and money…..
For those of you who had never seen a Koni Red (Special) – it is nothing very different than a Koni Yellow (Sport). Same body length, same body diameter, same shaft diameter, same shaft length, same shaft travel, same 2 and ¼ turns from full soft to full stiff. The only two differences are the color (of course) and the Red has much bigger lower bushing, that is as big as the OEM damper’s bushing, while the Yellow has is pretty small. We will see later today how they perform against the rest. Compressing them by hand feels like the closest ever to the OE damper, but we will see what the dyno says.


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## BAMA TDI (Nov 26, 2002)

*Re: Koni Rosso are here .... (pyce)*

pyce, 
That is kinda weird. Over 20 years ago, I put a set of Koni Reds on the back of 1978 Toyota Corolla Liftback. I installed them myself. I forget what I set them on. Man did they improve that car's rear handling. It had leaf springs in the rear.
Wonder why Koni NA changed stuff. OR maybe the Koni Reds of over 20 years is different from the Koni Reds of today. Just a thought.
Regards,
John


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## sundaydriver (Jun 4, 2004)

*Re: Koni Rosso are here .... (BAMA TDI)*

Quick question: How comparable would Boge Turbo Gas be to Bilstein TCs? Since both manufacturers claim those models are comparable, I'm curious to see how close they really are.


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## pyce (Nov 7, 2001)

*Re: Koni Rosso are here .... (BAMA TDI)*


_Quote, originally posted by *BAMA TDI* »_ .....That is kinda weird. Over 20 years ago, I put a set of Koni Reds on the back of 1978 Toyota Corolla Liftback. I installed them myself. I forget what I set them on. Man did they improve that car's rear handling. It had leaf springs in the rear.
Wonder why Koni NA changed stuff. OR maybe the Koni Reds of over 20 years is different from the Koni Reds of today. Just a thought.
Regards,
John

John, I am little confused.... Perhaps I can not understand fully your post.... You said they were great in improving your car's handling, but then you wonder why Koni changed stuff? Changed stuff to what? Do you mean that they were stiffer than now? And if so, we do not know yet how stiff they are..... I am just having hard time to get your point. Could you elaborate more, please? Thanks.


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## pyce (Nov 7, 2001)

*Re: Koni Rosso are here .... (sundaydriver)*


_Quote, originally posted by *sundaydriver* »_.... How comparable would Boge Turbo Gas be to Bilstein TCs? Since both manufacturers claim those models are comparable, I'm curious to see how close they really are.

If someone send me a Boge turbo Gas - we will dyno it and you will know how they compare. I can even put it on the car and run the graphs, if the owner does not mind....


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## Cadenza_7o (Jan 23, 2001)

*Re: (BAMA TDI)*

John - 
Depending on the quality of roads you drive on daily, I would say that the stock dampers are useless after 50-60k. I replaced the mine with HD at 43k (rears) and at 65 (fronts) the pistons' movements were not smooth. The resistance was not even through out the length of the piston shaft. And they were very easy to compress using one finger. With Bilstein HD, you would literally have to lean your entire body to compress it. 
As for the choices you're considering, go with HD if you want better body control and handling. The HDs are excellent at speeds above 80 mph.








To retain oem ride comfort, go TC.


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## pyce (Nov 7, 2001)

*Re: (Cadenza_7o)*


_Quote, originally posted by *Cadenza_7o* »_ ......To retain oem ride comfort, go TC. 

..... And I thought that you are one of the few who reads in here.


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## sundaydriver (Jun 4, 2004)

*Re: (Cadenza_7o)*

I'm curious to see if there would be any takers as interested in the Boge test as I am. I need mine for my daily driver, otherwise I'd send them. I'm curious since Neuspeed couples the TCs with SofSports and I now have a set of SofSports I'm ready to put on my MKII's Turbo Gas struts that have 5k miles on them. Plus, the Turbo Gas struts I'm using were bought for a Corrado G60 (in an effort to get a little more stiffness for the buck), and they're being used on a GTi. The ride right now is ultra-OEM comfy.


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## John A (Feb 19, 2001)

*Re: (Cadenza_7o)*


_Quote, originally posted by *Cadenza_7o* »_
To retain oem ride comfort, go TC. 

whaaa?


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## alexb75 (Dec 29, 2002)

*Re: Koni Rosso are here .... (pyce)*


_Quote, originally posted by *pyce* »_
John, I am little confused.... Perhaps I can not understand fully your post.... You said they were great in improving your car's handling, but then you wonder why Koni changed stuff? Changed stuff to what? Do you mean that they were stiffer than now? And if so, we do not know yet how stiff they are..... I am just having hard time to get your point. Could you elaborate more, please? Thanks.

I think "by changing stuff" he meant why NA Koni didn't supply Koni Red anymore.


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## pyce (Nov 7, 2001)

*Koni Red vs. Koni Yellow..... check this one out!*

Koni Red …
More dyno and more surprises….
The good news is that the Koni Red are looking really good, at least “on paper”! Winston, you wanted Koni Yellow, but with OEM-like compression? Well, you have it! The compression values are close enough to OEM, just the curves look little different, so perhaps we will see how that affects comfort, but with no doubt we have the closest ever shot to OEM values in rebound AND compression! Here below you can see a quick Force vs. Displacement (the rest will follow tomorrow!). The colors the software assigns are quiet confusing, so I put “Red” and “Yellow” as to better view which curve belongs to which damper…… Yeah, the big surprise is (and I wish someone from Koni could do some explaining here) that the Koni Red are advertised (as seen from many links before) like “half way” the rebound offered by the Yellow….. we see below is not the case! Not only that, but the Reds actually have slightly higher rebound values on full stiff and full soft! At the same time, the compression is as advertised (or about there) – close to stock. Here it is:








The bad news is ……. Well, it is not really news, but it is just bad– I just want to understand why are they telling us BS on hundreds of websites and charts and so on, when the truth is quiet different?








Anyway, more graphs tomorrow and they go on the car tonight, so we see if graphs and real life go together….


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## BAMA TDI (Nov 26, 2002)

*Re: Koni Rosso are here .... (pyce)*


_Quote, originally posted by *pyce* »_
John, I am little confused.... Perhaps I can not understand fully your post.... You said they were great in improving your car's handling, but then you wonder why Koni changed stuff? Changed stuff to what? Do you mean that they were stiffer than now? And if so, we do not know yet how stiff they are..... I am just having hard time to get your point. Could you elaborate more, please? Thanks.

Pyce, 
Guess it was kinda garbled but to me it made perfect sense when I wrote it. Sorry for the confusion.







I guess what I meant was, are the Koni Reds of yesterday the same as the Koni Reds you can get today? It seems everyone can get Yellow Koni Sports just by them selves today, but if you want the Reds you have to purchase a complete system. Am I understanding this correctly? Heck, I'm confusing myself now. IIRC, when I purchased the Konis around 1979-80, they were the only Koni's available at that time. There were no Yellow Konis that I can remember from back then. I don't know when they came out. (the Yellows) It seems to me Koni came out with the Yellows to supplement the Reds, Kind of like now you can get Bilstein HDs and TC Sports. If this is more confusing, let me know. I don't mean to be. I am enjoying what you are doing and listen to you and the others discuss the graphs and everything. I can say this. Learning is occurring on my part. http://****************.com/smile/emthup.gif 
Regards, 
John


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## Ceilidh (Jan 7, 2004)

*Re: Koni Red vs. Koni Yellow..... check this one out! (pyce)*


_Quote, originally posted by *pyce* »_Koni Red …
The good news is that the Koni Red are looking really good, at least “on paper”!.....The compression values are close enough to OEM, just the curves look little different, so perhaps we will see how that affects comfort, but with no doubt we have the closest ever shot to OEM values in rebound AND compression! Here below you can see a quick Force vs. Displacement .......
The bad news is ……. Well, it is not really news, but it is just bad– I just want to understand why are they telling us BS on hundreds of websites and charts and so on, when the truth is quiet different? 

Great stuff, Peter! By the end of your test drive tonight, I guess we'll know what has the greater effect on comfort: the compression level, or the shape of the rebound curve (interesting....the Reds look to have a much more pronounced knee, and they don't show the rebound hysteresis effect that the Yellows had -- that is, the curve looks slightly more "German", and the shocks might not have the "softening" effect on continuously bad roads that the Yellows display......but then again, the compression is a lot lower!!). Please let us know what you find!
As for the "bad news", I actually wouldn't take it as such; not at all: I've seen test plots of Konis on another car, and it had something much closer to the relationship shown on the Koni website --- yes the VW Golf relationship appears to be very different, but it in fact is kind of comforting that Koni hasn't replicated a "generic" Yellow/Red relationship for every type of car, but has instead taken the time to do something different for each one.







In any case, the burning question for me is *why* have they done it this way for the Golf/Jetta???
Looking forward to your report, Peter!!
- W


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## alexb75 (Dec 29, 2002)

*Re: Koni Red vs. Koni Yellow..... check this one out! (pyce)*


_Quote, originally posted by *pyce* »_Koni Red …
The bad news is ……. Well, it is not really news, but it is just bad– I just want to understand why are they telling us BS on hundreds of websites and charts and so on, when the truth is quiet different?








Anyway, more graphs tomorrow and they go on the car tonight, so we see if graphs and real life go together….


GREAT STUFF! 
I was just wondering though... our Dyno is only at 18in/sec... and it's perfectly fine for our comparison purposes. But, what I am wondering is that if the behavior could be the same at different speeds? Would the curves look the same Peter? When Koni publishes charts... what speed do they measure them at?!
I think that's probably why dynoing is not as effective as test drive or accelerometer!


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## pyce (Nov 7, 2001)

*We have a winner!*

Well, I hope to never eat my words back and will go ahead and say that We Have A Winner! http://****************.com/smile/emthup.gif Put the Reds tonight (on full soft) and drove around (on the designated track which we use with the accelerometer) and the thing is just fantastic. I am talking here a pure pleasure and spot on OE comfort! I would dare to even say that the comfort actually "appear" (it feels so far to be) even slightly better than OE. I do realize these are strong statements, but it is really what my butt tells me...... I was so surprised, so decided not to wait till tomorrow and went for about 40 miles drive on the concrete too. Spot on there too! Again, it sounds pushy, but it really felt like it was even better than what I had early in the day (rear OEM dampers). Of course, this is only half of the whole picture as the fronts are still the OEM (the Reds are only on the rear) but at this point I am pretty confident that if they managed to match the rears this close (and perhaps somehow make them better) then perhaps the fronts will be up ot the same level of matching. Needless to say that at this point we will try the fronts too, so to have complete picture. But so far so good.... in fact it never been this good with anything aftermarket that went in through all this time! If the Front Red do show the same results as the rears - then would be pretty save to announce that we have found at least one damper that is a pure OE replacement! Even more, it allows some sort of rebound adjustment that makes things only better as it gives options. It could be the only damper that offers actually OE ride when needed and very Sporty ride (and handling) when cranked up. The interesting part is that while feels very comfortable on all sorts of bump, holes, joints, etc - at the same time when doing slalom or fast direction changes - it feels like there is more rebound than OE and even than the Yellows. I do realize that this also sound pushy, but it is what I felt tonight. It basically managed to kill some of the free floating and mini movements the the OE "offers" but without sacrificing the comfort! How exactly is this achieved - we will find out from seeing later more graphs, I guess. But it feels like that. Winston, I think you particularly should have this damper! Can only wonder what would be when we start the 1/4t urns, etc. Do not even care at the moment, as the main goal was to find at least one pure replacement for the OE and I think we did it! I was ready to give up and this was the last damper we had hopes for - and I am thankful that it delivered even better than what we expected. I do understand that it will be pain to obtain, as it is not sold directly here, but who knows - there are many vendors reading here and someone may have luck in convincing Koni to let go. I myself can help whoever wants a set through my Italian contact, but the problem is that the Euro is freaking strong right now and is not going to be cheap. My plans are to go Phil's place this weekend and to open both Red and Yellow and see what is the difference inside and see if Phil can basically (and cheaply) "convert" an Yellow to the Red's characteristics - this way perhaps people can buy the Yellows from here (cheaper than getting the Reds from Europe!) and then send them to Phil for cheap "revalve". The nice part is that the Yellow are externally adjustable in the front - so it makes them much more attractive. But let's see how the week goes. I am sure we all can figure some easy way to get around this. Ideally, we can them externally adjustable (the rears) and this way in few seconds everyone who decides to go this way, could have pure OE ride or pretty Sporty setting for a fun weekend, etc. The important part is really that we finally managed to find a higher quality (I hope!), lifetime warrantied, pure OE replacement! The rest are just benefits on top of that








On another note - the HD arrived tonight! Man, that packaging was the most beautiful pack I have ever received







With those printed roses on the cover, my wife thought it was a wedding gift from someone..... what a disappointment when we opened it and inside was just a damper! LOL







So, tomorrow we will know more about the HD too! thanks again to the man who sent it, on his expanses, all the way from the East! http://****************.com/smile/emthup.gif


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## edisonr (Oct 24, 2003)

*Koni Red vs. KYB ?*


_Quote, originally posted by *edisonr* »_Looks like the Koni Reds are softer than the KYB's; do I have the right impression?

I wrote that before I realized I was looking the graphs for the Koni Reds and KYB's at different speeds (30"/sec and 18"/sec).
Now looking into both Koni's graph, there is almost no difference in compression from soft to stiff settings; most of the difference in on the rebound. Does this mean that comfort is related to the rebound characteristic of the damper?
Last question Pyce, how would you rate the Koni Red againts the KYB AGX?


_Modified by edisonr at 5:57 AM 12-1-2004_


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## Cadenza_7o (Jan 23, 2001)

*Re: (pyce)*


_Quote, originally posted by *pyce* »_
..... And I thought that you are one of the few who reads in here. 

Sorry gang, I shoulda said, "oem-like comfort". Your graphs may show a gap between Boge/Sachs and TC dampers but for folks who have used them, the difference is insignificant... as opposed to HD or Koni set on stiff. Most say the TC provides "slightly" better body control.
Given the choices that John's considering (TC and HD), should I have recommended the Bilstein HD instead?










_Modified by Cadenza_7o at 1:40 AM 12-1-2004_


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## Ceilidh (Jan 7, 2004)

*Re: (Cadenza_7o)*


_Quote, originally posted by *Cadenza_7o* »_
...graphs may show a gap between Boge/Sachs and TC dampers but for folks who have used them, the difference is insignificant....

Hi Cadenza,
I think what Peter is referring to is his real life experience with the TC's, in which he found them to be much, much less comfortable than OEM on concrete freeways and on continuously bad secondary roads (indeed, much less comfortable than the KYB's or the (full-soft) Koni Yellows in those situations). Isolated bumps were evidently not bad, so perhaps differences in road conditions (asphalt vs. concrete; isolated vs. continuous bumps) might explain why people report different things about the TC comfort.
Hope all's well! - C


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## Ceilidh (Jan 7, 2004)

*Re: Koni Red vs. Koni Yellow..... check this one out! (alexb75)*


_Quote, originally posted by *alexb75* »_
GREAT STUFF! 
I was just wondering though... our Dyno is only at 18in/sec... and it's perfectly fine for our comparison purposes. But, what I am wondering is that if the behavior could be the same at different speeds? Would the curves look the same Peter? When Koni publishes charts... what speed do they measure them at?!
I think that's probably why dynoing is not as effective as test drive or accelerometer!

Hi Alex,
A very good point!! Peter's shown me some of his data at other dyno speeds (note for people just joining in: "the 18.0 in/sec" etc. number refers to the maximum speed the shock hits in a given dyno run, so each run actually gives a whole range of velocities); the curves do look a little different in the "nose" region (the low-velocity part of a Force-Velocity graph).
At some point Peter will show the other runs, but the curves are very messy and it'll take him time to "clean them up" into a form that's actually readable by non-engineers (we really should be paying him for all the work he's doing!). It'll be easier to see with the graphs in front of us, but basically.....the faster dyno speeds (e.g., 18 in/sec, 30 in/sec, etc.) show how the shock responds to sudden motions and to a rapid series of bumps, whilst the slow dyno runs come closer to steady state.
No inside info on what Koni uses when it publishes its charts, but we'd guess (from the shape of the curves, and from general marketing considerations) that they'd most likely show a steady-state curve.
Good luck with finals, Alex!
- C


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## blackflygti (Sep 19, 2001)

*Re: We have a winner! (pyce)*


_Quote, originally posted by *pyce* »_delivered even better than what we expected. I do understand that it will be pain to obtain, as it is not sold directly here, but who knows - there are many vendors reading here and someone may have luck in convincing Koni to let go.

This is really weird. I know lots of people (up here in Canada) that have been buying Koni Reds over the last few years. They're not hard to get AFAIK. Try contacting H2Sport (Vortex Canadian Forum sponsor). They should be able to help you out. I was at the shop last week and they had a set of mk1 Koni Red rears on the shelf.
EDIT: Sorry, my mistake. I just checked Koni's North American catalog and i see that they don't offer Koni Reds for Mk4 VWs.










_Modified by blackflygti at 11:11 AM 12-1-2004_


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## Ceilidh (Jan 7, 2004)

*Re: Koni Red vs. KYB ? (edisonr)*


_Quote, originally posted by *edisonr* »_
.....looking into both Koni's graph, there is almost no difference in compression from soft to stiff settings; most of the difference in on the rebound. Does this mean that comfort is related to the rebound characteristic of the damper?....

Hello edisonr,
I think Peter's experiences thus far are showing that comfort depends upon both compression and rebound. The Reds appear to be more comfortable than the Yellows because their compression is less; conversely, Peter & I (and Alex, Placenta, and others) have found that very small tweaks to the Yellow rebound damping can have a huge effect on comfort.
For what it's worth, most of the textbooks imply that rebound tuning has a bigger effect than compression; that appears to be because compression damping is typically (for passenger cars) used primarily to control the unsprung mass, and thus can usually be set at a low level that doesn't strongly jerk the chassis around on bumps. Conversely however, the rebound (again on passenger cars) is used to control the chassis motions, and is set about as high as comfort allows. In effect, rebound starts off closer to the comfort "limit", and hence small tweaks make a noticeable difference.
In any case, even though compression tends to be ignored in discussions of ride comfort, if it's too high, the ride will nonetheless be bumpy. With the Koni Yellows, where the compression is almost twice as strong as OEM/Red, it's compression that's the problem, comfort-wise.
The question then becomes, why is the Yellow compression so high? Earlier we had suggested that maybe the compression is high because the Yellow has a big range of rebound adjustment (i.e., that perhaps the compression has to be high so as to match the rebound at full-stiff). But Peter's latest dyno runs show that the Red range of adjustment is every bit as big (slightly bigger, in fact) as the Yellow range. So something else is at work here.
Possibilities here include:
1) The Yellow compression damping is strong because it has to control the heavy aftermarket wheels & tires that "performance" enthusiasts often mount on their cars.
2) Or, perhaps it's strong because it's intended for "high-performance" use by people who presumably care less about ride comfort, and who would thus benefit from the better turn-in, dive/squat, and transient response that stiffer compression can give you (note: whilst rebound is typically 2X-3X stiffer than compression in passenger cars, in some race cars it's approaching 1:1 --- you do get some handling benefit from stiffer compression (up to a point!), but the ride really suffers...).
3) Or maybe the Red "full-stiff" adjustment is not intended to be ever used (even Koni says something to the effect that "rarely if ever will the shock need to be set at full-stiff), and so the compression is set to complement the softer settings; whereas the Yellow will be used at or near full-stiff with some aftermarket springs, and hence the compression has to match.....
4) Or maybe there's some other reason we don't know about yet!








Anyway, more kudos to Peter! -- if the Reds can be dialed up for better handling without the ride comfort falling apart, this option might become very interesting for a lot of people!
- Ceilidh


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## TyrolSport (Mar 4, 1999)

*Re: Koni Red vs. KYB ? (edisonr)*

From the performance drivers perspective(my own







) The Koni yellow compression is only adequate. I wish I could combine the Bilstein Sport compression with the adjustability of the Koni.......oh well.


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## porterdog (Feb 19, 2002)

Killer thread. I don't have a lot to add but wanted to mention two things: 
1. The AGX dampers fitted to my turbo Miata seem to have a HUGE difference from soft to hard. Also, it's common (on those cars at least) for people to find that ride comfort is better at the higher settings.
2. I didn't see any mention of 'downjacking' which can result from a series of bumps combined with too-high rebound damping. Basically, this occurs when the rebound damping doesn't allow the car to return to its nominal ride height before the next impact occurs. This eats up more travel, and with several subsequent impacts one can be left with no travel at all. Not uncommon on lowered Miatas which have precious little travel in the rear to start with. It can lead to real complaints about ride comfort.
$0.02,
Robert


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## pyce (Nov 7, 2001)

*Re:*


_Quote, originally posted by *edisonr* »_ …. how would you rate the Koni Red againts the KYB AGX? ….

Koni Red are pure (and arguably slightly better!) OE replacement. Arguably, because I can not prove it, but they indeed feel (put another 50 miles this morning in the mountains) like the is more rebound than OE, so the direction changes are more solid and flatter than the OE, but at the same time they do retain the OE comfort on all the crap variety we have here. I have no idea (at this point) how this is achieved, but it is some wonderful blend of comfort and some sort of stiffening when zooming around. Some of you may remember when we (with Winston) were changing the rear rebound of the Yellows by 1/8 of a turn from soft, to try to find some magic spot where comfort remains almost the same (as full soft) but the body motion gets a touch of “sporty-ness” from the slight increase in rebound…… And then we found out that the ¼ turn from full soft (on the Yellows) kind of gives this sort of magic. Basically at that ¼ turn you have the most “comfortable” sporty feel and if you go up, it gets even better, but starts losing comfort. If you get lower, maintains the comfort, but kind of loses the “sporty-ness”…….. Well, The Koni Red so far, on full soft, feel like that balance we found at ¼ from full soft on the Yellows! Caution here – I ma not saying that the Red on soft correspond to the Yellow on ¼ turn! They do not. The comfort of the Red is OE, the comfort of the Yellow is far from that! The feel of “handling improvement” on full stiff on the Red is as the feel of “handling improvement” on ¼ from soft on the Yellows! It may not make sense, but this is the best explanation I can find for the moment….
Now, the KYB AGX are not OE replacement. The accelerometer graphs prove it. But it is the first-close to OE. It is more comfortable than Koni Yellow on full soft – the butt says it and the graphs prove it. At the same time, thought, it has a lot more rebound than the Yellow at full soft – so the feel of “handling improvement” is there! I do realize this may be little bit confusing and the answer you want to hear is more simple, with few words and decisive, so I will try to say this (but only tests later will confirm it!) – If Koni Red is at 1 in comfort and 1 in “handling”, then the KYB would start at 3 in comfort and perhaps at 3 in “handling”, and it will reach (at its full stiff) at 4 in comfort and let’s say 5 in “handling”. I hope this somehow answers your question. However, something tells me that with tweaking the Reds later, we would be able to achieve what the KYB offers. The Reds just start “much lower” and perhaps would go “much higher” than the KYB AGX, but it is pain to adjust. So, in conclusion I guess it would be safe to say that the KYB (performance wise, not else!) would really be a “Narrower Range Konis for Less than Konis” But again would like to remind that these were tried on a car with 15” tires, OE springs and no bars, etc. So, things may dramatically change when you go lowered springs, big wheels, phat bars, etc. I really do not want to mislead anyone, pointing them to wrong purchase, so when it comes to the KYB, the safest suggestion would be to try them first, take a ride in car, etc. When it comes to the Red thought, I feel much more comfortable to tell people to get them, as they achieve the OE ride quality at leas ton one of their settings and I guess can only get better from here (handling wise) when you go up with the rebound adjustments. They may still not be any near a pure track damper, but let’s face it – majority here are not into competing professionally, so we are talking “improved handling” on ordinary streets, on daily drivers. So, all we are looking for is the “magic blend” between the “car feels great” and “the car feels so comfy”. The Reds so far are the only one we tried that fits in these somewhat controversial descriptions. Hope this helps some….

_Quote, originally posted by *Cadenza_7o* »_ ..... Your graphs may show a gap between Boge/Sachs and TC dampers but for folks who have used them, the difference is insignificant... 

This is precisely why the decision to use an accelerometer was taken! So, to exclude the opinion and to compare data. I absolutely understand what you are saying – folks rave about those and swear was the best thing after sliced bread - but that is part of the problem – the “folks” who we do not know about, how sensitive they are, where they drive, what else they have tried, etc. Let’s go to the wheels world as many of you know better what happens when you upsize a wheel….. I know folks that went from 15” to 17” on a VW A4 and said: “There is no difference in ride comfort!” … Now, would you all agree on that one? So, it comes down to how sensitive an individual is to begin with, but it also comes down to where do you drive that car. In a perfect world with perfect roads (and there are many states with those!) I would absolutely agree that 15” and 17” may provide almost the same comfort – but start running on concrete or streets with potholes and then let’s talk again…… Comfort is something we can go 100 pages for and still not conclude anything. Therefore we have the accelerometer and the graphs – so our opinion no longer matters, our different sensibility no longer matters – it is data, which is really hard to argue with. This said, I am not here to convince people what they need or should buy – we are just trying to extract some info from all we have and put it in perspective, so everyone can draw his/her own conclusions and go with what they think is best for them. If Billy-Bob feels great on a set of TC Sport – more power to him! It is all down to the individual. People ride on slammed down Weitec Coilovers and tell me it is better than stock (!) – sure, if that is what makes them happy – more power to them! To me the TC is poor damper, it is cheap and rides like cheap. Butt proves it, data proves it. The whole world may disagree, but I have to say it for the records as it is my experience. Everyone is absolutely free to decide for themselves!









_Quote, originally posted by *tyrolkid* »_From the performance drivers perspective(my own







) The Koni yellow compression is only adequate. I wish I could combine the Bilstein Sport compression with the adjustability of the Koni.......oh well.

According the dyno guy (Phil) it is not going to be very hard to do so. Perhaps you can send him yours and he will do it for you. Let’s wait for today’s dyno of the HDs and see what really the compression is, so he can match the Yellows to the same values. Of course, a Koni Rebuild Center could do the same, but Phil is not very expansive, so I guess you may be better at the end with him.

_Quote, originally posted by *porterdog* »_ 2. I didn't see any mention of 'downjacking' which can result from a series of bumps combined with too-high rebound damping. Basically, this occurs when the rebound damping doesn't allow the car to return to its nominal ride height before the next impact occurs. This eats up more travel, and with several subsequent impacts one can be left with no travel at all. Not uncommon on lowered Miatas which have precious little travel in the rear to start with. It can lead to real complaints about ride comfort.....

The down-jacking as you said, was covered slightly in the longer thread few months ago. On the A4 chassis and stock springs it is not really an issue with even strong rebound settings on the Yellow, but it may become and more noticeable with the Red, as the compression is less. More tests would tell, but so far on 0% stiff in the rear there is nothing like that happening.


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## edisonr (Oct 24, 2003)

*Re: Re: (pyce)*

Pyce, thanks for the comparison. I see (I think) what you mean with having a higher range of adjustability with the Koni Red, with a starting point that is OEM comfort; where the KYB AGX don't offer such wide range but they still deliver a good compromise between comfort and spottiness.
If is not a problem, could you post a graph of the Koni Red and KYB AGX showing displacement vs. force at 18"/sec for both settings (stiff and soft)?
Thanks again for this thread and I do agree we should paying you for all this work http://****************.com/smile/emthup.gif


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## pyce (Nov 7, 2001)

*Koni Part Numbers*

Before someone asks about the part numbers, here we go:
For VW MkIV (Golf, Jetta, NB from 98 on)
Koni Red (Special):
Front *87-2571*
Rear *80-2761*
Koni Yellow (Sport)
Front *8710-1337 Sport*
Rear *80-2761 Sport*
Note: The rear Red and Yellow have the same number, the difference is just the word *"Sport"* behind the number on the Yellows.


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## pyce (Nov 7, 2001)

*Re: Re: (edisonr)*


_Quote, originally posted by *edisonr* »_.... I see (I think) what you mean with having a higher range of adjustability with the Koni Red, with a starting point that is OEM comfort; where the KYB AGX don't offer such wide range but they still deliver a good compromise between comfort and spottiness..... 

You nailed it!

_Quote, originally posted by *edisonr* »_.... If is not a problem, could you post a graph of the Koni Red and KYB AGX showing displacement vs. force at 18"/sec for both settings (stiff and soft)?

Later today I will try. Not so free now and hoping to make it in time for the HD's dyno....


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## Occams_Razor (Jun 28, 2003)

*Re: Koni Part Numbers (pyce)*


_Quote, originally posted by *pyce* »_Before someone asks about the part numbers, here we go:
For VW MkIV (Golf, Jetta, NB from 98 on)
Koni Red (Special):
Front *87-2571*
Rear *80-2761*
Koni Yellow (Sport)
Front *8710-1337 Sport*
Rear *80-2761 Sport*
Note: The rear Red and Yellow have the same number, the difference is just the word *"Sport"* behind the number on the Yellows.

Now it is just a matter of finding someplace to get them without getting screwed on the price!


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## Cadenza_7o (Jan 23, 2001)

*Re: Re: (pyce)*


_Quote, originally posted by *pyce* »_
This is precisely why the decision to use an accelerometer was taken! So, to exclude the opinion and to compare data. I absolutely understand what you are saying – folks rave about those and swear was the best thing after sliced bread - but that is part of the problem – the “folks” who we do not know about, how sensitive they are, where they drive, what else they have tried, etc. Let’s go to the wheels world as many of you know better what happens when you upsize a wheel….. I know folks that went from 15” to 17” on a VW A4 and said: “There is no difference in ride comfort!” … Now, would you all agree on that one? So, it comes down to how sensitive an individual is to begin with, but it also comes down to where do you drive that car. In a perfect world with perfect roads (and there are many states with those!) I would absolutely agree that 15” and 17” may provide almost the same comfort – but start running on concrete or streets with potholes and then let’s talk again…… Comfort is something we can go 100 pages for and still not conclude anything. Therefore we have the accelerometer and the graphs – so our opinion no longer matters, our different sensibility no longer matters – it is data, which is really hard to argue with. This said, I am not here to convince people what they need or should buy – we are just trying to extract some info from all we have and put it in perspective, so everyone can draw his/her own conclusions and go with what they think is best for them. If Billy-Bob feels great on a set of TC Sport – more power to him! It is all down to the individual. People ride on slammed down Weitec Coilovers and tell me it is better than stock (!) – sure, if that is what makes them happy – more power to them! To me the TC is poor damper, it is cheap and rides like cheap. Butt proves it, data proves it. The whole world may disagree, but I have to say it for the records as it is my experience. Everyone is absolutely free to decide for themselves!









I do like and appreciate your empirical approach in drawing out the shock valving differences between various makes/models. However, TC has always been known as a small improvement over the stock crap from Boge/Sachs. If anything, VW should have fitted TC as stock. So far, more TDiClubers have opted for TC than 'Texers. 
Here's their take: http://forums.tdiclub.com/show...87142
So what is the conclusion of OE replacement now - KYB or Koni Red?
Edit: looking forward to the Bilstein HD graphs.










_Modified by Cadenza_7o at 2:23 PM 12-1-2004_


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## pyce (Nov 7, 2001)

*Re: Winston....*


_Quote, originally posted by *Ceilidh* »_ …. For what it's worth, most of the textbooks imply that rebound tuning has a bigger effect than compression….

I think in a way we can use the TC Sport vs Koni sport example…… just for an example, thought, because there are other things that do play in there which we have not fully covered. But anyway, if we look at the graphs, the Yellow has significantly more compression than the TC Sport and the the same time the TC Sport has significantly more rebound than the Yellow when set on full soft. Well, in this configuration (on full soft) the Yellow rides significantly better than the TC Sport. Accelerometer graphs show that….

_Quote, originally posted by *Ceilidh* »_ The question then becomes, why is the Yellow compression so high? ……..Possibilities here include:
1) The Yellow compression damping is strong because it has to control the heavy aftermarket wheels & tires that "performance" enthusiasts often mount on their cars.

You may have a very good point here, because when I was looking at the Italian site for the part numbers, the Reds are not offered for MkIV with “Sport Package”, but only the Yellows are. The Reds are sold only (officially) for 1.6 and 1.8 (non-turbo) and all diesels. So, according to Koni, if you have a VW A4 with “Sport Package” you *should* be driving Yellows instead of Reds. I have some sort of “SP” springs on mine, but do have light 15” wheels too – so perhaps that is why I can get away with whatever “horrible” would happen if Reds are used with Sport Package”







Would be nice if someone gets a set of those, with big wheels and the likes and see what that gives, then we will know more.

_Quote, originally posted by *Ceilidh* »_ 2) Or, perhaps it's strong because it's intended for "high-performance" use by people who presumably care less about ride comfort, and who would thus benefit from the better turn-in, dive/squat, and transient response that stiffer compression can give you (note: whilst rebound is typically 2X-3X stiffer than compression in passenger cars, in some race cars it's approaching 1:1 --- you do get some handling benefit from stiffer compression (up to a point!), but the ride really suffers...).

Perhaps that is true too. Even if lots of folks get the “Sport Package” because (at least time ago) was the only way to get the 17” wheels, etc. Of course, you could always get the regular car and put the wheels after that, but many folks do not know or do not want to the hassle, etc. So, they see it at the dealer, like it and get it as it is – it has the “SP” in it, but they do not care. So, later on they want ot change the dampers and the shop tells them “If you have the SP – then you get the Yellows as Koni recommends that”, so she gets the Yellow and has the ride we know about, which she does not need neither wants, but because Koni decided like that – she gets is like that. People like Tyrolkid are in entirely different paragraph. Perhaps real high performance people would not even like the Yellows, let alone the Reds. So, perhaps with the Yellows you do not really impress “her” with comfort and you do not impress “him” as pure performance. With the Reds, thought, you could at least get “her” to like her ride, so I do not fully understand Koni’s “suggestion” guide…..

_Quote, originally posted by *Ceilidh* »_ 3) Or maybe the Red "full-stiff" adjustment is not intended to be ever used (even Koni says something to the effect that "rarely if ever will the shock need to be set at full-stiff), and so the compression is set to complement the softer settings; whereas the Yellow will be used at or near full-stiff with some aftermarket springs, and hence the compression has to match..... 

They may have used the exact same parts inside and just modify the washers’ thickness for the compression and leave the rebound washers and the whole mechanism the same, so to be cheaper and less parts numbers to mess with in the production process, therefore we have the same rebound. Guess we will find out more when we take them apart. That is at least what the dyno suggests. Then again – you crank as much as you want the rebound, but at certain point (especially with soft springs) may not work anymore as it will start do the “down-jacking” as said above and then you have to back off, while with the Yellow you can keep going little bit more I guess….

_Quote, originally posted by *Ceilidh* »_ 4) Or maybe there's some other reason we don't know about yet!









I sent a link to all the related companies in this thread, and hopefully the e-mails will be forwarded to someone from the engineering department (that was my request) and perhaps we will have some more answers….. even if I doubt they would bother with us. But hope is always last to die.


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## Reigenhardt (Jan 31, 2003)

*Re: Re: (Cadenza_7o)*

2002 Golf. The rear TC's are total junk if you don't drive on marble floors. They are great on the highway, but as soon as you get on regular roads with crevices, holes etc, it is jarring and noisy. You say to yourself, did I just run over a curb?







What the hell were they thinking with these things. They are not OEM replacements. For some reason, from what I have read, these are more suitable for the Jetta than the golf in comfort. I won't put these in the car again.


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## pyce (Nov 7, 2001)

*Re: Cadenza_7o*


_Quote, originally posted by *Cadenza_7o* »_I do like and appreciate your empirical approach in drawing out the shock valving differences between various makes/models. However, TC has always been known as a small improvement over the stock crap from Boge/Sachs…..

Sorry, but the way I read the above written is this: “I do like and appreciate the data, but to me what people say is more important”. TC has always been known, because TC has been always advertised as such. The power of suggestion is a big thing.









_Quote, originally posted by *Cadenza_7o* »_ …… If anything, VW should have fitted TC as stock. 

I am so thankful they did not! If you want to spend a nice weekend in the Bay Area, come visit me, I will take off your HDs and will put the TCs on your rear for an afternoon. We drive around and you make your own conclusions. Then we drive my car with whatever dampers are left in the garage and you will have the chance to experience what I am talking about. Send me an IM if interested.









_Quote, originally posted by *Cadenza_7o* »_ ……So far, more TDiClubers have opted for TC than 'Texers…….. Here's their take…… 

Again (and I hope no one gets this personally!) – you have ten people that test drive the same car and all ten tells you it feels like 150 HP engine….. then someone shows you a dyno graph that indicates such engine is a 100 HP power plant – which one you take?

_Quote, originally posted by *Cadenza_7o* »_ So what is the conclusion of OE replacement now - KYB or Koni Red?

The bolds is the essential you are looking for:

_Quote, originally posted by *pyce* »_ *Koni Red are pure (and arguably slightly better!) OE replacement*. Arguably, because I can not prove it, but they indeed feel (put another 50 miles this morning in the mountains) like the is more rebound than OE, so the direction changes are more solid and flatter than the OE, but at the same time they do retain the OE comfort on all the crap variety we have here. I have no idea (at this point) how this is achieved, but it is some wonderful blend of comfort and some sort of stiffening when zooming around. Some of you may remember when we (with Winston) were changing the rear rebound of the Yellows by 1/8 of a turn from soft, to try to find some magic spot where comfort remains almost the same (as full soft) but the body motion gets a touch of “sporty-ness” from the slight increase in rebound…… And then we found out that the ¼ turn from full soft (on the Yellows) kind of gives this sort of magic. Basically at that ¼ turn you have the most “comfortable” sporty feel and if you go up, it gets even better, but starts losing comfort. If you get lower, maintains the comfort, but kind of loses the “sporty-ness”…….. Well, The Koni Red so far, on full soft, feel like that balance we found at ¼ from full soft on the Yellows! Caution here – I ma not saying that the Red on soft correspond to the Yellow on ¼ turn! They do not. The comfort of the Red is OE, the comfort of the Yellow is far from that! The feel of “handling improvement” on full stiff on the Red is as the feel of “handling improvement” on ¼ from soft on the Yellows! It may not make sense, but this is the best explanation I can find for the moment…. 
*Now, the KYB AGX are not OE replacement*. The accelerometer graphs prove it. But it is the first-close to OE. It is more comfortable than Koni Yellow on full soft – the butt says it and the graphs prove it. At the same time, thought, it has a lot more rebound than the Yellow at full soft – so the feel of “handling improvement” is there! I do realize this may be little bit confusing and the answer you want to hear is more simple, with few words and decisive, so I will try to say this (but only tests later will confirm it!) – If Koni Red is at 1 in comfort and 1 in “handling”, then the KYB would start at 3 in comfort and perhaps at 3 in “handling”, and it will reach (at its full stiff) at 4 in comfort and let’s say 5 in “handling”. I hope this somehow answers your question. However, something tells me that with tweaking the Reds later, we would be able to achieve what the KYB offers. The Reds just start “much lower” and perhaps would go “much higher” than the KYB AGX, but it is pain to adjust. So, in conclusion I guess it would be safe to say that the KYB (performance wise, not else!) would really be a “Narrower Range Konis for Less than Konis” But again would like to remind that these were tried on a car with 15” tires, OE springs and no bars, etc. So, things may dramatically change when you go lowered springs, big wheels, phat bars, etc. I really do not want to mislead anyone, pointing them to wrong purchase, so when it comes to the KYB, the safest suggestion would be to try them first, take a ride in car, etc. When it comes to the Red thought, I feel much more comfortable to tell people to get them, as they achieve the OE ride quality at leas ton one of their settings and I guess can only get better from here (handling wise) when you go up with the rebound adjustments. They may still not be any near a pure track damper, but let’s face it – majority here are not into competing professionally, so we are talking “improved handling” on ordinary streets, on daily drivers. So, all we are looking for is the “magic blend” between the “car feels great” and “the car feels so comfy”. The Reds so far are the only one we tried that fits in these somewhat controversial descriptions. Hope this helps some….


_Quote, originally posted by *Cadenza_7o* »_ Edit: looking forward to the Bilstein HD graphs.









Do we really need those? I mean, the whole world says they are the best? ….. Sorry, could not resist







I hope you are having build-in sense of humor, so we can get along for the rest of the trip. Come on, it is fun!








edited to fix a quote ....


_Modified by pyce at 3:08 PM 12-1-2004_


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## pyce (Nov 7, 2001)

*Re: Re: (Reigenhardt)*


_Quote, originally posted by *Reigenhardt* »_2002 Golf. The rear TC's are total junk if you don't drive on marble floors. They are great on the highway, but as soon as you get on regular roads with crevices, holes etc, it is jarring and noisy. You say to yourself, did I just run over a curb?







What the hell were they thinking with these things. They are not OEM replacements. For some reason, from what I have read, these are more suitable for the Jetta than the golf in comfort. I won't put these in the car again.









As of today I am not alone







Hope you did not say that just because you like me! LOL


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## Reigenhardt (Jan 31, 2003)

*Re: Koni Red vs. KYB ? (edisonr)*

BTW......I have stock springs on a 2002 Golf. I do not have a stiffer set up. Is it normal to have road noise over less than perfect pavement with these TC's? And the right passenger side seems worse than the rear driver side. The whole hatch feels like it is going to rattle apart sometimes. Very disappointing after all these months waiting for my install. My OEM's were dead when I took them out and I'll tell you one thing, they felt better than the Bilstein rears. I think the fronts are well matched for the car.


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## alexb75 (Dec 29, 2002)

*Re: Koni Red vs. KYB ? (Reigenhardt)*

Hey Peter, on off topic question... after removing/installing all these shocks multiple times... did you ever have to change the screws for holding the shock (either the top ones or the bottom)? My mechanic says after a couple of more adjustments on mine, we need to change those screws?!


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## phatvw (Aug 29, 2001)

*Re: Koni Red vs. KYB ? (Reigenhardt)*


_Quote, originally posted by *Reigenhardt* »_BTW......I have stock springs on a 2002 Golf. I do not have a stiffer set up. Is it normal to have road noise over less than perfect pavement with these TC's? And the right passenger side seems worse than the rear driver side. The whole hatch feels like it is going to rattle apart sometimes. Very disappointing after all these months waiting for my install. My OEM's were dead when I took them out and I'll tell you one thing, they felt better than the Bilstein rears. I think the fronts are well matched for the car.









How long have you been driving on the new dampers? Give them a few hundred miles to wear in before you pass judgement. My Bilstein HD's softened up quite a bit after a month or so.
BTW, is it just general constant rattling that bugs you or is it the sharper noises when you go over expansion joints on bridges?


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## Reigenhardt (Jan 31, 2003)

*Re: Koni Red vs. KYB ? (phatvw)*

Not constant rattling no. It is just I live where there are crap roads. When you go over crappily filled potholes, expansion joints, potholes, the rear of the car takes these sort of items harshly. It makes noise, and it is annoying. I have had them on for 3-4000 miles. The right passenger side is the most noisy.


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## f1forkvr6 (Jun 10, 2002)

*Re: Koni Red vs. KYB ? (Reigenhardt)*


_Quote, originally posted by *Reigenhardt* »_The right passenger side is the most noisy. 

Reigenhardt - Unless the right passenger side damper is damaged, or not installed correctly, this makes no sense (unless most of the potholes you hit are on the road shoulder). Take a good look at this particular damper and make sure everything is as it should be.
Peter - regarding Winston's mention of the importance of rebound, this is more critical when looking at transitional handling qualities, rather than NVH qualities (I'm sure you know this already, but it bears being stated for the purposes of this thread). I too am looking forward to the HD graphs (a thousand thank yous for all of your time and efforts!), mainly to see what my preferred damper "looks like" compared to the rest of the dampers you've tested.


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## Cadenza_7o (Jan 23, 2001)

*Re: Cadenza_7o (pyce)*


_Quote, originally posted by *pyce* »_
Sorry, but the way I read the above written is this: “I do like and appreciate the data, but to me what people say is more important”. TC has always been known, because TC has been always advertised as such. The power of suggestion is a big thing.









Hehe.... read it anyway you want. I know graphs don't lie but graphical renditions of "ride quality" is tough to transpose. When I chose HD over TC for my NB, it was based on short drives of a couple local NBs with TC / stock springs / no rear bar / 16" wheels. My observation is like what most TDi guys and reviews here have reported... an improvement over stock but not quite performance. But for those who looked for OE replacement but insist on Bilstein quality, TC has not disappointed those in the SoCal NB club. Graphs are good but I also let my butt do the work. I can show you 2 sonic graphs of a Stradivarius violin and a $1000 one ringing at 400 Hz or a trumpet vs piano ringing at the same frequency? Can you tell which is which w/o hearing the instrument? Bet ya Leonard Bernstein can't tell either. Yet each is different from the other. 

_Quote, originally posted by *pyce* »_
I am so thankful they did not! If you want to spend a nice weekend in the Bay Area, come visit me, I will take off your HDs and will put the TCs on your rear for an afternoon. We drive around and you make your own conclusions. Then we drive my car with whatever dampers are left in the garage and you will have the chance to experience what I am talking about. Send me an IM if interested.









Been up there many times. When in SF, I prefer to be the passenger. My choice of car for SF is a Lincoln with a couple of dead bodies in the trunk.









_Quote, originally posted by *pyce* »_Again (and I hope no one gets this personally!) – you have ten people that test drive the same car and all ten tells you it feels like 150 HP engine….. then someone shows you a dyno graph that indicates such engine is a 100 HP power plant – which one you take?

True... looking at dyno graphs of the current Porsche Carrera S (3.8L boxer 6) and Corvette (6L V8 / 100 lb-ft torque advantage), you would think the Corvette is the faster car. But it ain't! 

_Quote, originally posted by *pyce* »_
Edit: looking forward to the Bilstein HD graphs. 
Do we really need those? I mean, the whole world says they are the best? ….. Sorry, could not resist







I hope you are having build-in sense of humor, so we can get along for the rest of the trip. Come on, it is fun!









Nah... we really don't need to. I have them and like them. Most of the discomfort (OE and HD) I blame on the design of the rear suspension and the 17" wheels. What I found surprising was my GF can't even tell the difference in harshness between the HDs and busted OE Boge/Sachs units... and she drives on the 405 (LA County section) everyday! The only things she could tell was the car steers better, leans less in the curves and high speed turns. If you were to show me graphs of OE vs HD dampers, I can't imagine buying HD. Know what I mean?


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## Ceilidh (Jan 7, 2004)

*Back to data*

Gentlemen,
May I ask that, having established there's disagreement over TC subjective ride comfort, perhaps we should move on?







Thank you!

- Ceilidh



_Modified by Ceilidh at 12:06 AM 12-2-2004_


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## pyce (Nov 7, 2001)

*Back to data*

Come on, people! Where are the bets on the HD vs. Koni Yellow?







I just got back form the dyno and feel like not posting the graphs at all, because no one would believe them, so this whole thread will be called absolutely wrong because the HD does not show higher compression, neither higher rebound than the Konis, but in real life everyone swears that a Koni even on full stiff would never get even closer to an HD








Beside the jokes, we spent like three hours tonight, going over and over and over with the tests because we could not believe the graphs and Phil (the dyno guy) wanted to make sure that we have more than one run to compare with, to eliminate possible mistakes, but there were no mistake,s I guess, because the different runs were pretty consistent among themselves. I know this is what 90% of you have been waiting for all this time, so we put more than the usual 18.00 graph and tomorrow I will post graphs at low speed (4.00) then medium speed (12.00) and then the 18.00 speed - all this in Force vs. Displacement and Force vs. Absolute velocity. There are few other things that the dyno showed, which are not easy to catch, but Phil told me where to look and is starting to make sense, but more on that after the graphs.


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## Ceilidh (Jan 7, 2004)

*Re: GTI-Neuspeed-Koni vs. R32 (alexb75)*


_Quote, originally posted by *alexb75* »_








Here's what I think: Less compression than Koni, way more rebound than softest, but less than stiffest Koni.
On the same stretch of road, it will have more ups/downs on accelometer than Koni... will be similar at big bumps as the Koni 50% just posted...
Let's see how wrong I am









Well, on the basis of Peter's preliminary report, it looks like Alexb75 will be winning the gold star.








(But no fair, Alex -- you're one of the few people (besides Peter) to have actually tried both Bilstein HD and Koni Yellow on the same car!)
Ok Peter, let's see how Alex does on the accelerometer test!!


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## alexb75 (Dec 29, 2002)

*Re: GTI-Neuspeed-Koni vs. R32 (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_
Well, on the basis of Peter's preliminary report, it looks like Alexb75 will be winning the gold star.








(But no fair, Alex -- you're one of the few people (besides Peter) to have actually tried both Bilstein HD and Koni Yellow on the same car!)
Ok Peter, let's see how Alex does on the accelerometer test!!









Merry Christmas to me then








I knew they have less compression... but think they had more rebound at lower Koni setting... very very interested to see the graphs!


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## Ceilidh (Jan 7, 2004)

*Re: GTI-Neuspeed-Koni vs. R32 (alexb75)*


_Quote, originally posted by *alexb75* »_
......I knew they have less compression......

Alex,
How did you know they had less compression? I've never driven on the HD/Sports (well, never on a VW) -- please tell me, what were the sensations that tipped you off about the compression? That is, what are the seat-of-the-pants characteristics of high (or low) compression that are distinguishable from high (or low) rebound? Your answer I'm sure will be interesting to a lot of us! (Peter, did you suspect the lower compression too? If so, how would you describe it?)
Thanks very much, Alex! 
- W


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## pyce (Nov 7, 2001)

*HD vs. Koni vs. The Rest.....*

Here is the first graph, the Force vs. Displacement at the 18.00 in/sec. There are more to come, at low and medium speeds, but we have to start form somewhere….








Below is an old graph that shows the Konis and full stiff and full soft, but with the OE and TC Sport, so posting it again may help you all to have an idea where the HD stands against the OE and the TC. You may note the TC Sport has actually higher rebound values than the HD on this speed. The other thing to note is that the HD absolute compression values are not much higher than the TC and the OE. Here it is reposted again:








Then someone would ask – But why is it that my HD are performing so well, the car stays so flat and most of all – I have this great feeling of telepathic turn-in, etc…… Well, there is an answer and I am glad I met this dyno guy (Phil) who gave me a very long lecture last night in racing vs. road driving, etc. Something tells me that our Winston would see these graphs and would be also able to explain all that, so, Winston, if you have time and desire, feel free to go ahead and write it – I would never be able to explain anything as well as you do anyway. Otherwise, I will try to find time later today and “try” to tell the story that Phil told me last night. Hope I will manage…


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## phatvw (Aug 29, 2001)

*Re: HD vs. Koni vs. The Rest..... (pyce)*

Nice work Pyce!
So if I am reading this correctly, the Bilstein TC actually has more peak rebound stiffness than HD? HD appears to peak at 225, while TC peaks at 275. TC, HD and OEM all have about the same peak compression stiffness, however the profiles are quite different. (hope I didn't reverse compression and rebound there...)
I would guess that HD's perform so well because the initial and final portions of the graph are a lot steeper instead of the more rounded profile of the others. Is there some kind of variable valving going on inside the HD?
It would be nice to see the Bilstein HD and Sport graphs side by side as well


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## pyce (Nov 7, 2001)

*Re: HD vs. Koni vs. The Rest..... (phatvw)*


_Quote, originally posted by *phatvw* »_ ....I would guess that HD's perform so well because the initial and final portions of the graph are a lot steeper instead of the more rounded profile of the others. Is there some kind of variable valving going on inside the HD?

Spot on! But there is pretty long and detailed explanation behind this, precisely, why Bilstein goes that way. Because he can open the damper and make the "steep initial portion" disappear very easy, but then it will not be "Bilstein" anymore. Two different philosophies to control the body motions, both with their pros and cons. I want to take some time and write about what he said and put couple of models to kind of visualize it, so it will be easier to comprehend (I guess and hope). 

_Quote, originally posted by *phatvw* »_ ....It would be nice to see the Bilstein HD and Sport graphs side by side as well









Agree. At this point we HAVE to do it. I am very interested to find out whether the valving is really the same as it had been advertised like this for ages. It is not easy to locate a damper thought. Ideally someone will send me one that has about 1.000 miles on it - that is what the HD has according to the owner. Anyone willing to help? Thanks


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## Cadenza_7o (Jan 23, 2001)

*Re: HD vs. Koni vs. The Rest..... (pyce)*

Peter -
I'm not trying to stir the pot here but don't these graphs imply that the TCs, once they moved beyond +/- ~0.75" - 1.00" of displacement, should out-perform the HDs. 
For example...
If I was to take a freeway entrance ramp that resembles a S-shape or a series of mountain curves at close to max grip, once the suspension is tucked in, the TCs should have faster "corner" speed than the HDs?


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## pyce (Nov 7, 2001)

*Re: HD vs. Koni vs. The Rest..... (Cadenza_7o)*


_Quote, originally posted by *Cadenza_7o* »_ …… don't these graphs imply that the TCs, once they moved beyond +/- ~0.75" - 1.00" of displacement, should out-perform the HDs. 
For example...
If I was to take a freeway entrance ramp that resembles a S-shape or a series of mountain curves at close to max grip, once the suspension is tucked in, the TCs should have faster "corner" speed than the HDs?

I am not really sure we can say that the TC will corner faster (once you have the full lean, or as you said, the suspension is “tucked in”)….. perhaps what we can say is that once the body starts rolling more than just the initial “kick-in” (where the HD are shining!) then it will take “longer” for the car to fully sit on the outer springs, because as pointed by you, the TC provide higher resistance in the longer run (after the initial “kick”). And this is precisely big part of what Phil thought me last night. The Mono-tube vs. Twin-tube, the Race (Track) Damper vs. the Street Damper. The earlier, quicker, but also weaker in the long run acting versus the later, slower, but stronger in the long run acting. Two different ways to (somehow) skin a cat, two different purposes, two different results. I just need to find some time for the modeling as it will be nicer and easier to say it (show it) later.


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## alexb75 (Dec 29, 2002)

*Re: GTI-Neuspeed-Koni vs. R32 (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_
Alex,
How did you know they had less compression? I've never driven on the HD/Sports (well, never on a VW) -- please tell me, what were the sensations that tipped you off about the compression? That is, what are the seat-of-the-pants characteristics of high (or low) compression that are distinguishable from high (or low) rebound? Your answer I'm sure will be interesting to a lot of us! (Peter, did you suspect the lower compression too? If so, how would you describe it?)
Thanks very much, Alex! 
- W

First of all, Greg Woo has mentioned something like that to me once.
Also, when I went from Bilstein to Koni... I realized that the smaller bumps are felt less, but bigger bump impacts are more on the Koni... but ONLY when I go OVER a bump and not when I come off. When I come off a bump, Bilstein was stiffer than Koni at below 3/4 turn! 
At last, MOST racers around here that had very stiff springs, they went with Koni as Bilstein was not able to dampen them enough... so I thought Koni (most probably) has higher MAX rebound/compression.
Therefore, my assumption that Bilstein had less compression but more rebound than Koni 33%.
This however, does NOT explain THE CURVE... as Peter is probably going to post, the rebound and compression values at different speeds/displacement are AS important as MAX/MIN numbers... So, the steepness of those curves play a big role as well. I leave this upto Peter to explain. http://****************.com/smile/emthup.gif 


_Modified by alexb75 at 1:59 PM 12-2-2004_


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## Cadenza_7o (Jan 23, 2001)

*Re: HD vs. Koni vs. The Rest..... (phatvw)*


_Quote, originally posted by *phatvw* »_I would guess that HD's perform so well because the initial and final portions of the graph are a lot steeper instead of the more rounded profile of the others. Is there some kind of variable valving going on inside the HD?

It's too bad that front dampers can't be tested on these machines. Since our cars are FWD and have a front weight-bias, front dampers have more influence on how the car handles. When I replaced my OE Boge/Sachs units with HDs, I intentionally threw out the rears first and drove the car for almost a year. They improved handling just a bit, but once the front were in... oh Mama!!! http://****************.com/smile/emthup.gif


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## pyce (Nov 7, 2001)

*HD vs. Koni - attempt to explain.*

Here is an attempt to explain….. I mean, to scratch the surface only. Take it very easy, it is not exactly how things are but an attempt to visually give a direction of the basics, the principles, the idea behind it.
For the purpose of this sole explanation, let’s visualize the dampers are mini-springs, because perhaps would be easier to visualize “weaker” spring and associate is with “weaker” damping force, etc. Again, a damper is not a spring, it is just a way to represent little bit of what I need as to explain something little here.
So, looking at the Page 1 we have our setup. The HD is the blue on the top. The Koni Sport is the yellow in the lower part. The car is presented as this tall poll that rotates around the axis in the bottom and has all the weight of let’s say 1.000 lb or kg (whatever you chose) that is concentrate on the top where the big red circle is. Here is the setup:









The Bilstein HD is acting immediately (as seen from the dyno graphs, the vertical line like no one before on the upper left corner, the beginning of the compression!) so, we make those blue balls much closer to the red body. That is indicated as Distance “A”. That damper has also lower absolute value (force) so let’s make that blue spring be “weaker” (smaller wire diameter, more coils, etc). 
The Koni Sport is acting with delay 9as also seen from the dyno graphs last posted, the not-so-vertical line in the upper left corner, the beginning of compression) so let’s make those yellow balls more distant than the red body. That is indicated as Distance “B”. This damper has more absolute value (force) so let’s make that yellow spring “stronger” (bigger wire diameter, less coils, etc.)
On Page 2 we have action! The driver touches the steering wheel in one direction and the car starts to roll in the opposite direction. In our case, the big, heavy red ball starts leaning towards the right. The HD is in contact immediately, the Koni is far from being in contact. Again, it is not like this in real life, as they are both always in contact, but this is a way that I believe is not so hard to comprehend what is going on.
On Page 3 (here below) the car keeps rolling. At this point, the HD is already acting as counter force to slow down the red ball. The Koni Yellow is barely making the first contact. So, what happens? At this point we have the red ball in the HD case already being slowed down (or not allowed to keep building inertia, and therefore becoming heavier and heavier with every part of degree it is rolling), while in the Koni Sport case the red ball is still going down strong and building even more inertia. Here is the pix:








On page 4 we have the final moment before let’s say the weight is “loaded” on the main spring. Again, it is not really like that, in real life the spring also acts right from the initial move, but for the purpose of this talk we will present it this way…… So, on this last part of the roll, the HD had been “preventing” the red ball to build inertia (or, preventing it to build a lot more inertia like the Koni’s case), meanwhile the Koni gets the much heavier “hit” (as nothing prevented the inertia to build so far). The HD is weaker, but started earlier, when it was “easier” and therefore the red ball does not “hit” the main spring with huge inertia. The Koni is stronger, but started later, when it was more “difficult”, therefore has to be strong enough to slow down a ball with much more inertia built-in by this last moment, as to allow the “hit” on the main spring to be with the same force.
The first (HD) allows quicker initial response, quicker transitions, quicker everything, but more nervous on not smooth surfaces! The “race” damper as Phil describes it. Great for the track. The negative part is that those two blue balls are so close to the body – there is not even minimum “free-travel” allowed, which makes transfer every single coin you go over on the freeway.
The second (Koni Sport) offers slower initial response, slower transitions, slower everything, but allows for more fluid, smooth driving on bad surfaces! The “street/sport” damper as Phil describes it. Great for the street, because those yellow balls are much further from each other, so there is plenty of “free travel” which makes it that going over the coins is some time not even noticeable. 
Hope it made some sense. To each it’s own decision. The question only is – for street use – are you willing to trade off some comfort for some quicker initial response? The “quickness” is in directions changes – the “comfort” is for the whole length of the drive (if the roads are not good, intended!). It is a compromise that everyone should make, aware of what it is to be gained and what to be lost. What we are trying to call “the educated choice”. Then if racing is the goal, of course, hands down a “quicker acting” mono-tube is what you need, but perhaps the HD could be re-valved so not to only offer the “built-in-the-design” quick response, but also higher absolute values of rebound and compression.


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## f1forkvr6 (Jun 10, 2002)

*Re: HD vs. Koni - attempt to explain. (pyce)*

A nice explanation, Peter, and precisely why I like using Bilstein mono-tube dampers. I am willing to put up with a bit of broken pavement NVH in exchange for a more responsive damper. That's always been an acceptable trade-off for me. Your analysis, explanation, and relevant comparisons should enable a Vortexer to make a more informed decision regarding which type of dampers they'd prefer. Another thread tucked away in my "notepad" for future reference http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif .
Now, I imagine the slow speed graphs comparing the HD to others will show additional differences, no?


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## pyce (Nov 7, 2001)

*Re: HD vs. Koni - attempt to explain. (f1forkvr6)*


_Quote, originally posted by *f1forkvr6* »_ ....Now, I imagine the slow speed graphs comparing the HD to others will show additional differences, no?

Actually they do not so clearly show what is well seen in the high speed. Yes, I will elaborate them later and post them, so nothing is "hidden", but fortunately the 18.00 was the one we most of the time used AND the one with the most visible "quick" vertical line that the HD showed. The lower the speed goes, the less difference is in those two lines (HD vs Koni). Perhaps that also explains why the faster you "yank" the steering wheel, the faster you want to bite the turn - the more the HD feel different than the rest. On a slow Sunday top-down drunk slalom there is not much difference which damper you use and the graphs show it. Need some time to make them pretty and you will see....


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## pyce (Nov 7, 2001)

*HD vs. Koni on lower and higher speeds....*

Here we have some more speeds (still Force vs. Displacement)....
Below is the 12.00 in/sec where the the difference in beginning compression is not so clear anymore. It is still there, but it needs a serious zoom-in to be seen and differentiate:








Contrary, the higher the speed, the clearer the different beginning of compression is. Below we have the maximum speed achievable with this dyno - the 30.00 in/sec. and for even better visualization only the HD and Koni on full stiff are shown. The Koni on full soft has identical compression line, so we can keep it out for this one:








Later will put the lowest speeds we got.....


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## Ceilidh (Jan 7, 2004)

*Re: HD vs. Koni - attempt to explain. (pyce)*

Hi Peter,
I had actually gone and written something up for you here, but you beat me to it.







Very nice intuitive explanation, and (as always!) stunning use of graphics! For 99% of the population, you've said about all that needs to be said -- so thank you!
That being the case, I'll just summarize the salient points below, for the 1% or so of the population (perhaps just you and me







) who wan things in more detail (all of it you already know -- it's for the benefit of the others!):
1) The force-displacement graphs are pretty deceptive, in that they visually over-emphasize the high-velocity part of the curve where the shock spends relatively little time. In something like the 18 in/sec or 30 in/sec plot, it looks like the Koni damping completely overwhelms the Bilstein in everything except a tiny little "steep/rounded" shoulder at the ends of the plot. But that's deceptive. When we convert the data into the Force-Velocity plot and focus on the velocities that actually pertain to chassis control & handling, that little "shoulder" expands into a fairly hefty region where the HD damping mostly matches or exceeds the Koni (especially in the low-velocity compression), and the seemingly enormous region where the Koni's much higher becomes a....well I wouldn't call it irrelevant, but it becomes a "bumpy-road" region far away from the area that dominates handling.
2) In this context, the striking thing about the HD plot is its "squareness": how the Force-Displacement curves show a really steep section near the endpoints, but which then "turns a corner" and rapidly flattens out. By contrast, the Koni F-D curve is much more rounded and slanted. When we eventually convert things over to the Force-Velocity plot, the HD should show substantially stiffer damping (again, especially in compression) at the low piston velocities, then a "kink" or "knee" and a sudden flattening out so that the high velocity damping is relatively low (this is what we earlier referred to as a "Germanic" curve). And again by contrast, the Koni will have a somewhat straighter/ less kinked curve, with less low-speed damping but more damping at the higher piston speeds.
3) For the on-the-road / on-the-track ramifications of these damping curves, we should consider pitch (dive/squat), roll, and bump behaviour separately. Roll and bump unfortunately get a little involved, but pitch is relatively easy: for a variety of reasons (length of wheelbase, moment arms, anti-dive geometry, etc.) the shock piston-velocities in pitch are pretty low. Thus the relationship is pretty straightforward: the greater the damping at the lowest piston velocities, the less the car will nose down under braking or "squat down" under acceleration. That's one major component of the "smooth & stable" feel that people report with the HD's -- the platform doesn't pitch nearly as much during acceleration and braking. As well, the strong shock-induced pitch resistance quickens the longitudinal weight transfer that occurs with braking and acceleration (basically, a spring effectively transfers weight only after it's compressed, which takes time; a stiff shock transfers it immediately). Thus a skilled driver who likes to use trail-braking/ throttle inputs etc. as an integral handling skill will find the HD-equipped car more incisive on turn-in and responsive to lift-throttle tuck-in and the like.
4) Before we look at roll and bump behaviour, however, we have to think in detail what happens at the wheel during roll or bump (and if you skip this part, what follows next will not make much sense; in effect, it's why Peter earlier today kept stressing that his spring-analogy is not quite what actually happens....)
a) We'll do roll first. When you crank the wheel into a long corner and the car begins to turn, the piston velocity at inside & outside shocks is initially zero. When you're fully in the turn and the car has "taken a set", it's heeled over as far as it will go in that particular corner, and the velocities are again zero (assuming a perfectly smooth road, of course). In between these initial and final states, the piston velocity has to ramp up to some maximum, and then back down to zero. Hence as you proceed into the corner, the piston velocities progress from zero - very low - low - low/medium - medium - low/medium - low - very low - zero (Note that we never get to "high", as the higher piston velocities are reached only on bumps, etc; note also that the above sequence merely gets us into the corner; when we exit, we go throught the sequence all over again).
b) So here's the basis of Peter's "spring-analogy" & graphics: We'll start with the Konis. As discussed above, the Konis have a relatively straight, slanted Force-Velocity curve, which means that the damping forces (even at very low velocities) will be roughly proportional to piston velocity. Thus when we turn into a long corner with the Konis, the damping forces fighting the roll progress from zero - very low - low - low/medium - medium - low/medium - low - very low - zero (i.e., just like the velocities.
Now, the next part will either seem blindingly obvious, or else completely arbitrary; if the latter, just take our word for it, as it's an aspect of control theory that's not worth diving into here







. But the effect of a damping force progression that's proportional to velocity is extreme smoothness: if the car begins to roll too fast (i.e., if it begins to lurch), the damping forces rise and the roll slows down; if the roll begins to unduly slow down, the damping forces fall and cease to fight the rolling quite so hard, and the rolling thus tends to maintain its speed. Now, the roll velocity has to start and stop at zero, so it will change -- i.e., it's not going to be perfectly constant! -- but between those start/stop endpoints, the rolling will be smooth and lurch free.
c) Ok, now before we can look at the Bilstein, let's first consider a hypothetical shock that has the Bilstein's "kinked" curve, but with much lower damping overall (e.g., what if the OEM shock had OEM damping levels, but a Bilstein HD curve?). This shock will be awful in roll, for the following reason:
As the car begins to roll, the piston velocity is low, and the damping is proportionally very stiff. So the shock successfully fights the rolling, and the car initially stays fairly flat. But as the g-forces build, the rolling velocity has to rise, and the damping forces rise to fight it -- so far so good. But if we've really dived into the corner, at some point the rolling velocity will rise past the "knee" in the damping curve -- and that's a problem: when we're above the knee, the damping curve is relatively "flat", and further increases in rolling velocity are not countered by corresponding increases in damping force. Or in plain English, the rolling velocity is suddenly free to really accelerate. Then, as the car nears its steady-state roll angle (i.e., the springs are finally beginning to do their job) and the rolling velocity drops back down below the "knee", the strong low-velocity damping suddenly kicks back in and "grabs" the car to stop the last bit of rolling.
So in this hypothetical awful car, you'll feel two distinct lurches as you turn-into a corner: whereas the rolling speed with the Koni goes [very slow - slow - medium slow - medium - medium slow - slow - very slow - stop rolling], the awful car will go [very slow - slow - FAST - FAST - suddenly slow - very slow - stop]. This will spill your passenger's coffee all over the cabin.
d) So why doesn't the awful progression happen with the HD's? Presumably it's because the HD's are set stiff enough at low-velocities that the velocities never have a chance to rise past the knee. As indicated by Peter's spring-analogy, the HD damping so immediately and so strongly resists the rolling that the progression is not only reasonably smooth, but the max rolling velocity is significantly lower than with the Konis. Or, if the rolling motion in the Koni was [very slow - slow - medium slow - medium - medium slow - slow - very slow - stop rolling], in the HD it'll be [very very slow - very slow - slow - slow - slow - very slow - very very slow - stop rolling]. On a smooth track, the HD-equipped car will thus feel very smooth and stable in roll (as well as in pitch).
.
5) So far the HD sounds like heaven: use a Germanic profile that's kinked enough to keep big bumps from smashing the passengers to bits, but with the low-velocity damping high enough that chassis motions never creep above the knee, and you'll have a wonderfully stable ride with great handling. So why does Peter hate it?








At this point I'm going to simplify things even further (yes, believe it or not, this post is actually "simplified"!) and just say something quick about bumps: we're told by everyone's shock literature that "chassis motions are controlled by low-velocity damping, and high piston velocities are excited only by bumps" -- well, that's true....but what doesn't often get said is that bumps not only cause high piston velocities, but they cause low velocities too. And therein lies the problem. If the road is smooth, the German curve is wonderful. But if the road is sufficiently imperfect.....
a) A sharp bump definitely causes high piston velocities -- but a long, low bump causes low piston velocities (which the HD strongly tries to fight). So too do very short, very rapid chatter bumps and fine road corrugations (with low enough amplitude, even high-frequency bumps cause low velocities). The former (long, low bumps & waves) cause head-toss: if the road is smooth but wavy (or even if the road camber keeps changing), the HD-shod car will follow every wave and toss the passengers about the cabin as the car leans first one way (because the road is leaning that way) and then the other (ditto). The latter (sharp but tiny corrugations) will cause a relentless "busy" harshness that bounces the car up and down in a non-painful but perhaps irritating fashion, with concommittant noise and vibration on continuously broken pavement....
b) Anyway, there are many types of bumps and many types of problems, but for an illustrative example, let's just look at what happens on a big bump -- one that causes high piston velocities. Let's look closely at the up & down motion of the wheel as it hits and then crests the bump: initially (just before it hits the bump) the shock is not moving, so piston velocity = 0; when the wheel is at the top of the bump and about to go back down, the shock is again not moving, so velocity again = 0. But in between the shock is moving very, very fast.....so the piston velocity has to progress from [stationary - very slow - slow - medium - fast - very fast - extremely fast - very fast - fast - medium - slow - very slow - stationary].
c) Ok, do we need to say much more? The shock absorber tries to fight the motion, and as it does so it pushes the car upwards (and thus you feel a bump). With a shock that's "linear", the upward motion on a bump smoothly progresses in proportion to the shock speed: it goes [nothing - a little - medium -more - medium - a little - etc.....]. But with a non-linear, Germanic shock, you again feel two lurches (actually, you feel 4: 2 on the way up, and 2 on the way down): the upwards kick is initially strong, then it suddenly falls away when the piston velocity exceeds the "knee", then it suddenly kicks back in when the wheel nears the top of the bump, then the car is yanked downwards by the start of the rebound, then the force again falls away as the rebound velocity climbs, then the yank comes back as the wheel stops rebounding.
In practice, the above series of kick-lurch-kick-yank-lurch-kick-stop will happen so rapidly (on a sharp bump) that you won't be able to discern it (any more than you can see the individual frames in a motion picture film -- they shoot by too fast). Instead, it'll just interact with all the various resonances and compliances in the car and suspension to make for an overall harsh, noisy ride.
d) In contrast, a more "linear" shock like the Koni will make the bump feel more or less like the bump -- that is, the upward forces are proportional to the piston velocities, so you feel a jolt that smoothly rises to a peak and then gradually falls away. It'll still be there -- but it'll be much smoother and less cacaphonous.
. 
Anyway, I don't want to end on a sour note: the Germanic (HD) profile exists for a reason: it's an excellent way to make a car handle very well on a smooth Autobahn or a good track (or a good road in many parts of the U.S.). The ride will be acceptable, and the car will be so stable and unfussed by maneuvering that to many the ride can feel even better than stock (the OEM shock will always allow more float, heave, and sway). But the OEM-style (or Koni-style) damping curve also exists for a reason: on less perfect surfaces, it lets the wheels follow the road with much less upset to the cabin.
Ok, that's it for general theory; now back to the real data...








- Ceilidh


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## darisd (Dec 20, 2002)

*Re: HD vs. Koni - attempt to explain. (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_
Ok, that's it for general theory; now back to the real data...










Awesome analyses! I have been waiting to see how the HD fits in for a while. I would like to see an accelerometer graph comparison if possible. Peter, you said you needed a full set of shocks first right? I wish I had some sitting around, but I am waiting to see how this "pepsi test" turns out to buy two cars worth of shocks...


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## alexb75 (Dec 29, 2002)

*Re: HD vs. Koni on lower and higher speeds.... (pyce)*

Simply AWESOME! http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif 
Your graph and explanation was just PERFECT... I cannot believe how creatively you explained the situation there!
One thing I noticed from this graph:








The steepness of rebound curve on full-stiff Koni at higher speeds is even more than Bilstein... which confirms my amazing turn-in with Konis at 75% stiffness... ofcourse Compression is another story as Koni adjustments doesn't change it. This sums up how I can characterize each. 
- If we set both shocks at SAME stiffness level (koni around 33-50%), Bilstein handles better because of the fast reaction we saw. 
- However, at higher Koni settings the advantage goes to Koni as you can see from the graph and has been proven to me on track where I got simply amazing fast reactions when I was at 75%... HOWEVER, 75% is NOT livable on the streets.
So, if someone can do the pain in the a$$ adjustments of rear Koni for each track session and then again for street use, he can have the best of both worlds... faster reaction times on track, slower reaction/handling while having that little more comfort on the street. If one likes a sporty damper with fast reactions who doesn't mind feeling most roads irregularities, then Bilstein FITS the bill perfect.
*Koni: *--> If willing to adjust
- Greater performance on track with 75% or more stiffness
- Less handling than Bilstein on the street with livable rebound setting
- More comfort than Bilstein at lower rebound settings 
*Bilstein:*
- Handles better and reacts faster at comparable stiffness as Koni (33-50%)
- Is a better street handling shock
- Less comfy than Koni at similar stiffness (on the street)
- Less relative performance vs. very stiff Koni on track
_*Note:* This has been my own conclusion from trying both Bilstein and Koni (on same spring rates), both on street and track, and also from following this and some other related threads... and I still dont know nothing







_


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## Cadenza_7o (Jan 23, 2001)

*Re: HD vs. Koni on lower and higher speeds.... (alexb75)*


_Quote, originally posted by *alexb75* »_
The steepness of rebound curve on full-stiff Koni at higher speeds is even more than Bilstein... which confirms my amazing turn-in with Konis at 75% stiffness... 
- If we set both shocks at SAME stiffness level (koni around 33-50%), Bilstein handles better because of the fast reaction we saw. 
- However, at higher Koni settings the advantage goes to Koni as you can see from the graph and has been proven to me on track where I got simply amazing fast reactions when I was at 75%... HOWEVER, 75% is NOT livable on the streets.

Porsche has also been using Koni on their limited production cars like the 944 Turbo S, which was tuned as a track car but drivable on the streets when the dampers are adjusted accordingly. Koni is also the fav brand among Porsche drivers, especially those weekend warriors. There are Bilstein users too but they usually have the dampers custom-valved. 
Ultimately, maximum stiffness is crucial for performance.


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## ruking (Apr 4, 2003)

*Re: HD vs. Koni on lower and higher speeds.... (Cadenza_7o)*

"Ultimately, maximum stiffness is crucial for performance."
I also would agree, I think the benefit of this thread is to get folks to look at (the objective data to aide in the subjective judgement) what they think they want/need with what they think they like and what they will really live with, actually be doing, etc., and the trade offs. Sometimes these things are not congruent.








For me, it is fair to say that if the oem struts and shocks did not "deteriorate" as fast as they do, they would be fine for a (I am SWAGGING here) majority of users. So really, one of the operative things than can be done here is really to identify an oem replacement that lasts longer than the oem







(READ: lifetime warranty) A side benefit would be better performance.




_Modified by ruking at 4:48 PM 12-3-2004_


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## pyce (Nov 7, 2001)

*HD vs. Koni - Force vs. Absolute Velocity*


_Quote, originally posted by *Ceilidh* »_ ...... When we convert the data into the Force-Velocity plot and focus on the velocities that actually pertain to chassis control & handling, that little "shoulder" expands into a fairly hefty region where the HD damping mostly matches or exceeds the Koni (especially in the low-velocity compression), and the seemingly enormous region where the Koni's much higher becomes a....well I wouldn't call it irrelevant, but it becomes a "bumpy-road" region far away from the area that dominates handling......

Here is the conversion you are talking about. I knew you would not just let this go without seeing it







Thank you very much for the deep analysis above! ..... I was wondering - there is really not much literature specifically about automotive dampers (or I just failed to find it? but really looked hard!) - so, would you consider actually presenting your posts (with some boost of graphs, etc) to a publisher? Something tells me this could be a very nice "Car Dampers for Beginners" book. What do you think?


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## pyce (Nov 7, 2001)

*Re: (ruking)*


_Quote, originally posted by *ruking* »_...... So really, one of the operative things than can be done here is really to identify an oem replacement that lasts longer than the oem







(READ: lifetime warranty) A side benefit would be better performance......

Last post on page 5.


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## ruking (Apr 4, 2003)

*Re: (ruking) (pyce)*

Yes, page 5, for those who like the long version, (war and peace) page 7, for the readers digest version.


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## phatvw (Aug 29, 2001)

*Re: (ruking) (ruking)*


_Quote, originally posted by *ruking* »_Yes, page 5, for those who like the long version, (war and peace) page 7, for the readers digest version.









Koni Red (only available in Europe)


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## pyce (Nov 7, 2001)

*Koni Red in USA*

Actually, if someone really wants them badly, they can get one of the Vogtland Kits from US. It comes with lowering springs and Koni Red. The springs could go in the Classifieds later to get some cash back. I fI am not mistaken, the whole thing comes to around 600$ for the Kit, but I see it is not so easy to sell lowering springs nowadays, so the Reds may end up costing from 500 to 550$, which is still not that bad for what the damper offers.


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## The Kilted Yaksman (Oct 31, 2000)

*Re: (ruking) (phatvw)*


_Quote, originally posted by *phatvw* »_Koni Red (only available in Europe)

So, for an easily available OEM replacement, since we don't have any data on the Tokico HP or the KYB GR-2, the KYB AGX would be the best choice?


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## pyce (Nov 7, 2001)

*Re: (ruking) (The Kilted Yaksman)*


_Quote, originally posted by *The Kilted Yaksman* »_
So, for an easily available OEM replacement, since we don't have any data on the Tokico HP or the KYB GR-2, the KYB AGX would be the best choice?

Not really. The KYB AGX is stiffer than OEM Jetta, which will make it even worse for a Golf. It could be one of the "most comfortable" aftermarket dampers, but it is not OEM replacement. 
We have actually decided (with Phil, the dyno guy) to walk the whole walk and I just got back from his place where we spent good part of the day playing with the Koni Yellow. He opened them and changed the washers several times and we dyno the "new valving" versus the old and it is amazing how with just the diameter and thickness of a washer inside, the whole picture changes dramatically! The goal is to bring the Yellow to the Red valving (which actually happened very easy!), so in the future if any of you guys decide to get Reds - all it needs to do is buy used Yellows and send them to Phil for the re-valve. I have no idea what is he planning to charge, but I am sure it si going ot be much less than Koni Rebuild Center. He is actually making (as we speak) a special holder, so he can put the Front Damper on the dyno as well - this way we can get some front dampers dyno graphs and also he can do the re-valving on the Yellows to become like the Reds. So, this thread is far form over, as the fronts are to come. The nice part is that the Yellows are externally adjustable (the fronts) so this way ones can have externally adjustable Reds







HE can actually do the rears also externally adjustable, but it is some hardware work that may be more expansive, so it may not be for everyone...... More to follow.


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## jpop (Feb 16, 2004)

*Re: (ruking) (pyce)*


_Quote, originally posted by *pyce* »_
So, this thread is far form over, as the fronts are to come.









I have been following this thread for awhile and must commend everyone involved (including vortexer opinions) to the time, thought, effort, and explanation put herein. This and other threads encourages my enthusiam for owning a VW/Audi everyday (even though this thread pertains to shocks). This thread further emphasizes the use of REAL world data opposed to SAID data, as I am a firm beleiver in numbers w/ proof/validity (ex. dynos and applicable graphs). http://****************.com/smile/emthup.gif for the great work and future developments.


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## pyce (Nov 7, 2001)

*Inside the Koni .....*

For those who wonder what is it inside those Koni Dampers, here is a quick model of the Compression “Valve”. This is just to grasp the concept – the actual design is very, very close, but did not want to waste too much time to reproduce it precisely. Anyway, tomorrow there will be pictures of the whole damper take apart, so it will be easier to see how exactly it looks. So, here is the concept:








There is this sort of disc (1) that has lots of small holes in with specific diameter and specific amount, placed on specific diameter. On top we have one of the most important washer (2) that is “slotted” as seen on the picture. It is 22 mm diameter and only 0,4 mm thickness! It is as thick as this line here in the way you see it on the screen right now: _____________ Then we have the washers (3) that are also 22 mm diameter and 0,4 thick, but have no slots. On top of it is a bolt, that holds these three washers firmly on the plate (1). It is very important how much the bolt pre-compresses the washers on the plate (1), but let’s ignore this part for the moment and imagine that the part (1) is flat and the washers are sitting flat on it.
This whole thing, that is so small to enter your pocket and you do not feel it inside, is basically the whole freaking “Compression Valve”! How does it work? Here is an attempt to explain it with few simple words. On the picture below we have it assembled (the top two pictures) and on the picture below we have some sort of section while it is assembled:








The whole thing is actually mounted up side down, so when the compression occurs in the damper, the oil is pushed by the piston down, but on this picture it is going “up”. Just imagine the picture in real life is upside-down. So, what happens…… for the small movements, the oil “bleeds” through the small “cuts” on the washer (2) and that allows the piston to compress easier, so we have nice comfort level in that initial moment of the stroke, where the “low speed” is. Once the speed rises up, those small “cuts” are no longer enough as the pressure becomes higher and higher – so the whole three washers “bend”, so more oil can go through at faster speed. Once the pressure goes down (slowing down the speed) the washers get back to their original flat form, closing all gaps except where the small “cuts” are. If someone can’t imagine the “bending” of the washers – get in hands a CD and imagine that is the washer. Put your finger in the hole and with the other hand’s all five fingers get the CD on the edges and press and release, like trying to slide it further on the finger in the hole……. That pretty much is it how our Koni works. Someone now will say “Dude, this is more simple than my bicycle!!!” …and indeed it is. But Winston would say: Getting this simple mechanism to work exactly as intended - and with any degree of consistency between manufacturing runs - is not an easy thing! It's actually reassuring that the mechanism is so simple, as it bespokes a lot of engineering elegance & durability.” ……
The Rebound “Valve” is more or less the same thing. You have a stack of washers just like the compression valve, the only difference is that you have a spring that sits on top of the last washer! So, the mechanism is such that when you adjust your Konis from full soft to full stiff – you are basically turning a screw by about 2 full turns. So, when the screw is tighten more, it pushes the spring harder on the washers, so the washers do “bend” harder as now there is a spring on top of them that helps them not-to-bend so easy. So, the harder they “bend” means the less oil will go through – meanwhile the piston wants to go as fast as it wants, but it can not as the washers “bend” less and less, so less and less oil, more and more “force” to move that oil – and we have higher rebound forces. Simple as that!








So, how do you “re-valve” these things? Pretty damn simple, yet very complex. Simple, because (if you look at the first picture) you just take one of the washers (3) and replace it with thicker or thinner or with smaller diameter washer and that is it. Why is it complex? Because one washer less does not mean 50% less compression. Apparently it is quiet a science to “guess” the thickness, amount of washers, diameters, etc. And anyway, this is only part of the equation. By modifying the washers, you change the values of those graphs we have been seeing (from the dyno) but if you want to change the “shape” of those curves, then the disc (1) also has to be modified, the amount of holes, the shape of the holes, etc. The nice part is that there is a software, that is precisely for these cases. You input the amount of washers on your damper, the diameter, thickness, etc and then the software tells you what kind of other washers you have to put in there as to achieve your reduction or increase of compression/rebound values! I took some pictures of that software and will try to put them later on. Will put also pictures from the actual parts, so perhaps it will make all this clearer


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## releger (Dec 5, 2004)

*Re: HD vs. Koni - attempt to explain. (pyce)*

Hi Peter. This is Robert. For other readers, I'm the supplier of the Bilstein HD that Peter has recently tested. I thought I would try to make a connection between the test results and my subjective impressions of having the HD in my car. First, let me offer a bit of background. I'm not new to VWs. I've owned an '82 Jetta and a '92 GLI, both of which had Bilstein HD with stock springs. I was quite satisfied with the results. On both cars, the ride was firm but comfortable enough for daily use on New England roads. My most recent VW is a 2003 Jetta Wagon. When the OEM shocks started to wear I decided on a set of Bilstein HD since my previous experience was positive. I bought the set and installed the rears. Unfortunately, I found that the ride was significantly stiffer than I was expecting under some circumstances. I experimented with tire pressures, but swapped back to the stock shocks after two weeks of use. So, my subjective impression is that the Bilstein HD for the A4 VW rides firmer than the Bilstein HD for the A1 or A2 VW. There are other factors to consider, such as the brand of tires and the fact that I'm older now and might be more sensitive to an excessively firm ride than I used to be. The '92 was a daily driver for me until a little over a year ago, but the shocks had over 200k on them when I got rid of the car and they may have softened slightly in their advanced age. One other factor is that I only installed the rear HDs on the wagon while I left the fronts as stock. On both my previous cars I had installed all four in one shot. I'll address this point further below.
The HDs are not all bad. They do some things very well. As the OEM shocks loosened up, the wallowing and floating while driving on the highway got worse. The HDs cure that immediately. They offer a feeling of being very connected to the road. They are able to effectively damp very small motions of the suspension, as described above by Peter's diagrams. There is no excess motion. On relatively smooth roads, the absence of wallowing is actually more comfortable to me than OEM.
The conditions where I found the HDs annoying on the wagon:
1. Certain sections of highway pavement which undulate up and down with just the right frequency and amplitude cause the car to follow too closely the undulations. This up-and-down motion is very irritating to the passengers. It feels like being inside a big salt shaker. On my daily commute, I hit a couple of sections of highway like this. The stock suspension just follows these undulations while the body of the car floats over them. This behavior agrees with the test data. The HD is a very firm shock at low piston velocities and only moderately firm at higher piston velocities. The pavement undulations never cause the shocks' piston velocity to go above the region in which they are very firm and the excessively damped response is uncomfortable to the occupants. I wonder whether the fact that I only installed the rears might be a factor in this case. I remember from reading the very long 30-page thread that Peter started long ago, that there was discussion of the effect of significantly different damping front and rear. I think it was Ceilidh that wrote that certain suspension tunings that cause pitch when hitting bumps are less comfortable than tunings that cause the entire car to move up and down in unison. So, with my stock shocks in the front, the front end of my car is floating over the undulations while the HDs in the rear are causing the rear end to move up and down with the undulations. The resulting motion is a form of relatively high frequency pitch. If the front of the car were to follow the undulations closely like the rear, the car would not be moving up and down in unison, but the motions might be a bit more random with less pitch component. The only way to know for sure will be to install all four and do some testing.
2. Certain moderately sized bumps can be quite harsh. This could be a large road imperfection while traveling city streets at low speed, or it could be a relatively smaller road imperfection while traveling on the highway. The highway situation seemed more annoying because of the contrast between the smooth well damped ride at speed on good pavement and the sharp jolt and accompanying noise from hitting the pothole, expansion joint, etc. The stock suspension floats over these imperfections with little upset and much less noise. Ceilidh above described how the HD, when hitting a road imperfection, can go from low velocity high damping, to high velocity low damping, to low velocity high damping on both compression and rebound, with the resultant acceleration/deceleration forces involved causing uncomfortable chassis motion and vibration. This seems like a very good explanation for what I'm feeling subjectively.
3. Speed bumps taken above a very slow speed can be extremely annoying. When taking a speed bump too fast, the rear tires actually leave the pavement and the rear end comes crashing down with a bang. The weak stock rear springs are not able to extend the shock quickly enough to keep the tires in contact with the road surface after leaving the speed bump. The rear end then falls from a height of a couple of inches before the tires make contact. The relatively slow vertical motion of the rear end of the car means that the HD is still in its low velocity/high damping region resulting in high damping forces when the tires come down. I was quite surprised when this first happened. Given the amount of the jolt, it may be possible that the rear bump stop is coming into play as well.
4. I did occasionally feel some of the "head toss" effect, but it did not feel too bad on the wagon. The fact that I only installed the rears probably reduced the amount of this effect I felt. I typically only felt this on city streets and not on the highway.
The test data do explain one observation that I had with the HDs on my two previous VWs. While having the HDs on the car with stock springs, I found it easier than I thought it should be possible to bottom the front suspension when hitting a pothole while braking for an exit ramp. I thought that shocks that stiff should prevent the bottoming, but it turns out that at higher piston velocities, they are not very stiff at all. So with the nose down a bit under braking taking up some of the front suspension travel, the road imperfection pushes the shock into the high-velocity part of its response where it offers only moderate resistance, and bang!
I just recently mounted snow tires. Even with the stock shocks, the snows have a noticeably softer ride than the OEM Michelins. I'll probably try mounting the rear HDs again in the spring before removing the snow tires just to see the effect of a softer tire with the HDs. I'm expecting it will help impact harshness, #2 above, but probably not the others. Experimenting with lower tire pressures with the OEM Michelins reduced impact harshness, but the "salt shaker" effect didn't change much.
I'd like to thank Peter for all of the work that he has done to understand the qualities of the different dampers available for the A4 VW. I'd also like to thank Ceilidh and others for their contributions to the analysis of the experimental data. There is so much complexity behind the curves that the shock dyno generates. You guys have done an extremely good job of describing what the diagrams mean and how the results relate to suspension behavior on the road. I've learned a great deal by reading this thread. This information will help the VW community to make an informed choice when it comes time to repair or upgrade suspension.
The Koni yellow modified to reduce compression damping looks like a great option for a comfortable ride with the bonus of being able to do some fine tuning on the car. I'm looking forward to how this story unfolds!


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## Ceilidh (Jan 7, 2004)

*Re: HD vs. Koni - attempt to explain. (RecaroWagon)*

Robert,
Your post deserves a very full reply (of which more anon), but for now I'd just like to say that yours is perhaps the most articulate piece of writing that has graced the Vortex in some amount of time. I don't know what you do for a living, but it's truly a pleasure to read such well-crafted English prose (and the information conveyed is first-rate too, which is a matter for a later date!). Thanks very much for writing, and I/we look forward to commenting on your posts later this week. All the best!
- Ceilidh


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## releger (Dec 5, 2004)

*Re: HD vs. Koni - attempt to explain. (Ceilidh)*

Ceilidh, thanks for the kind words. I look forward to reading your reply.


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## pyce (Nov 7, 2001)

*Koni Yellow - First Re-Valve and some results...*

Last night the front damper adaptor was ready and running, so we could for the first time dyno a front damper. It was very surprising to see that the absolute values of a front damper are not by far bigger than those of a rear (from same make, model, etc). Several tests were performed, all with, of course, different “valving” and different oil. Here is more or less how the testing went (let’s separate each step, so it will be easier to get reference later):
1. Base run was done, so to know where Koni Yellow Front (Original valving, Original Oil) stands. The results could be seen in the graphs to follow. This damper is the one with named on the graphs as “Koni Front Original”
2. The top 22 mm washer (refer to a picture posted few posts ago) was removed and an 11.4 mm washer (thick 0.6 mm) was installed. So, we now have the “bleed” washer (22mm x 0,15 mm), then the original first washer (22mm x 0,4 mm) and then this new, smaller but thinker washer on top. The pre-compression was set to the original Koni Yellow value. A new oil was used, a 10W weight, which according to Phil is closer to the European oil the Konis come with. The result is some lost in absolute compression values, maintaining the “curve” of the compression. The damper is named “V1.0” (Version 1.0).
3. Third test was performed with everything exactly as in #2, but this time 5W weight oil was in the damper. The result is further lost in compression value, but not change in the shape of the “curve”. This damper is named below as “V1.1”
4. Then three in a row tests were done, leaving the 5W oil inside, but simply changing the “pre-load” on the washers (via the 5 mm screw that holds them bolted on the disc – refer to pictures about “valving” in a previous post). The impressive part was the 1/4 or a turn on the screw did show about 30-40 lb of absolute compression change at a time! So, small steps were in order to get the damper to perform as what you see as the lowest line (in compression) on the graph. Basically, this is the same configuration as in #3, but with just a small 5/16 turn of pre-load implemented! This damper is named below as “V1.2”
Here is the Force vs. Displacement:








Then we have the Force vs. Absolute Velocity:








Note: The rebound values of the Original Koni are little bit higher than the rest, but try to ignore them for the moment, as the damper we used for that base was set by default to something more than 0% stiff.
So, if all our mambo-jumbo thinking is correct – we now should have something like Front Koni Red damper. Someone would say “How do you know what the values of a Koni Red Fronts are?”…. Well, we do not know, as we do not have that damper, but we tried to use some sort of logic to get there. It may be quiet wrong, but it is the best guess we could make. Here is the “logic” behind the “V1.2” setting on the Yellow and why we think it should not be far from a Koni Red Front:
Looking at the graph below, we can see the curves from the Koni Yellow Front, Koni Yellow Rear and Koni Red Rear, that are all “original”. We can notice that the difference in absolute values between the Yellow Front and Rear is about 12 lb and the curves’ shape are pretty in line, no crazy stuff going on there. So, if we (in theory!) make the value of the Yellow V1.2 to be 5-6 lb above the value of the Red Rear, maintaining the same original curve shape – then perhaps we are close to a possible Red Front. Now, getting those exact 5 -6 lb is not really the easiest thing in the world, as the washers had to be “pre-loaded” several times before we even get here, but we are close enough for the first seat-of-the-pants (butt dyno), so to get some real life feelings for where we are. Therefore, the value now was left at about 4 lb more than the Red Rears, but later on it could be dialed spot-on (if needed)….









Well, this is so far for the first approach in “Revalving-101”. We will try to put them in today or tomorrow and see what happens ...


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## John A (Feb 19, 2001)

*Re: Koni Yellow - First Re-Valve and some results... (pyce)*


_Quote, originally posted by *pyce* »_
Well, this is so far for the first approach in “Revalving-101”. We will try to put them in today or tomorrow and see what happens ...










now the real fun starts. the 'does it act how we expect' phase.


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## alexb75 (Dec 29, 2002)

*Re: Koni Yellow - First Re-Valve and some results... (John A)*

I am not too sure what was the rebound curve for Koni front? If it's the one with max values, it's rebound is WAY higher than the Koni rear original (brown)> right? and your re-valved rear has close rebound values to front... 
To me, fronts are always felt softer.. but it just could be the independent design.


_Modified by alexb75 at 4:02 PM 12-8-2004_


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## pyce (Nov 7, 2001)

*Koni Yellow - First Drive of the Re-Valve and some dynos..*

Decided to go with Koni V1.2 only on the Left (driver’s side) and keep the right side OEM (Front) – just in case the whole re-valiving thing was way too off – so we pull out only one damper instead of two for more tweaking. But the new setting is not bad at all! Drove it for about 20 miles ( to the dyno place so we test the OEM Front and see where we are with the guess) and comfort wise it is very, very hard to detect difference from OEM. Then we dynoed it and it actually shows difference, but it is a good point to start because the “comfort factor” is quiet spot on – not bad for a very first trial, translating a dyno curve to a real life experience. Thumbs up to Phil who got it is close at it could have been without having OEM data to compare!
So, here we have (finally) a Front OEM Jetta TDI damper and related graphs. On the pictures below it compares to the Koni Yellow Original (the way comes form the factory) and to the Koni Re-Valved (we call it V 1.2 – the one with 5W oil and 5/16 preload on the washers):








Too much rebound? We will see. So far is not doing anything that could be noticed, so more driving needs to be done. Eventually will start “holding” the inner wheel up while accelerating out of turns, but it is going to happen at higher than 0% rebound (not doing it now!) and we have to find it where (if eventually) that occurs. Then of course the possible “jacking-down” but that is also to be seen on specific surfaces and specific rebound (higher than the 0% for now). What we need to do is to put the left one in there too and drive it for a week or more and get the “longer term” feel for it. After that perhaps we will have an idea what is good and what is bad, where to touch and where not to and perhaps V1.3 will be the one that mimics pure bone stock OE Front damper when on the softest setting and goes up from there…… The nice part is that at the moment there is nothing that “disturbs” the ride, so we are not far from what we are aiming for! 
Here is another graphs, same dampers as above, shown in Forece vs. Absolute Velocity configuration:








There are several more things to share, things like the OEM Front to Rear graphs, etc but will do that tomorrow.


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## Charles R (Oct 26, 2001)

*Re: HD vs. Koni - attempt to explain. (Ceilidh)*

Great thread Peter, and an excellent summary Ceilidh.
I always get nervous about how much time I'm going to have to spend in front of the PC every time Peter says, "Did you see this thread?"
But as always, great info. And a definate, "must read" for anyone who wishes to further their knowledge of performance handling.
And thanks Phil. I'll let Peter be a lone guinea pig a bit longer, but you'll probably be seeing my Yellows again.


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## alexb75 (Dec 29, 2002)

*Re: Koni Yellow - First Drive of the Re-Valve and some dynos.. (pyce)*

http://****************.com/smile/emthup.gif Cool... the Koni original setting is softest, right?


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## pyce (Nov 7, 2001)

*OEM Front to Rear ratio.....*

Here is the “ratio” between the Front to Rear OE damper graphs (Jetta TDI). The compression values are quiet close to each other, the rebound values are noticeably stronger for the front. Compare to our Koni V1.2 Front, we are “around there” with the compression, but the Koni original rebound was not touched, and it looks like around 100 lb stronger (in absolute values) than the OE front rebound. So, perhaps next step is to “lower” little bit the rebound value and perhaps not go to pure OE value, but leave it in between where OE and our Koni V1.2 is actually, maintaining the shape the same…
The OEM Front to Rear Force vs. Displacement is below:









Alex – yes, the Koni Original you see on these latest graphs is always on 0% stiff (the softest rebound available).


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## pyce (Nov 7, 2001)

*Re-Valving 101 .....*

Let’s go little bit deeper…..
Here is an attempt to explain the very basics of how this “valving” is intended to work. This is not exactly what we have in the Konis, but it is very close and all the drawings below are done for pure “talking point” and not actual “how to”. Later on there is the part that is actually an exact “how to” but it will be mentioned where the “virtual tour” ends and where the real data begins.
So, is a perspective cut of the very basic “compression valve” that we talked about several posts ago, This picture is purely to see the assembly in perspective, so to have a better idea of how it is done. In our invented scenario we will have first a single washer that sits flat (no pre-load with the screw that holds in position). The red arrows indicate where the oil pressure comes from:








Below we have the exact same situation, this time it is a straight front view, so it is easier to visualize the oil flow, the washer’s opening, the angles, etc. Se, we are moving to the two-dimensional drawings:








Above we have the washer closed and the oil starts pushing as the piston moves down (up in this drawing, for better visualization, but in real live this whole thing is upside-down from how it is seen here!) and compresses the oil as the washer is fully closed. That washer acts like a spring, so at certain point the oil pressure is built enough that the washer starts deflecting at the edges and some oil starts flowing through the created now gap all around the edge of the washer, as seen in the next picture below:








So, on this picture (3) we have basically the situation where the oil starts flowing and it depends on whether the piston continues to move faster or slower – the washer will keep opining or closing down. But let’s imagine that the piston keeps pushing down and even accelerates, so we are closely getting into a higher velocity range. Naturally, what happens is that the poor washer deflects even more (as more pressure is building) and therefore more oil is going through the even bigger gap that is opened now. The picture would look something like this below:








So, what happens next? Let’s say we like the way this damper performs at low speeds, it has very nice and easy initial stage, smooth opening due to the thin washer, but perhaps the high speed (that happens on picture 4) is little bit too “soft” – basically too much oil is allowed to flow when the pressure rises too much, due to the softer washer that provides too much gap at those pressures. So, what we want to do is to keep the initial opening (from picture 3) to be soft and easy, as to have nice comfy ride at low damper speeds (like highway cruising), but at the same time we do not want that washer to open that much when the pressure builds at the high speeds. So what we do is put a thicker, but smaller diameter washer on top of the one we have. As seen on the next picture (5) – we have the existing washer A and then the new washer B on top of it:








What happens now? The oil flows inside, the pressure builds and the thin washer edges start giving up, so the oil starts flowing again, as seen in the next picture (6):








This time, thought, the head of the bolt that holds the whole thing together is not longer the pivot point around which the washer flexes, but the pivot point moves to where the edge of the small washer (B) is. At this point the small pressure from the low speed would start lifting the edges of the big washer (A) but as soon as the opening grows even little bit, it will get harder to lift the bigger washer further, because now the inner half of the big washer is not allowed to flex as much as before because of the washer (B), which basically somehow acts like a screw with bigger head (even if in reality is not like this because the washer (B) still flexes some, while the head of the screw does not, but for the purpose of this scenario we can also interpret the washer (B) as a larger screw head)…. So, the washer (A) very soon builds more and more resistance as it is not allowed ot flex as before, so needs bigger force to keep deflecting it and at the same time the opening now is smaller than before as the inner part is no longer allowed to flex and the outer part can only flex much – therefore we have reduction in flow, which also means increase in pressure, The picture looks like this below:








Note: the inner red arrows are drawn to make like full circle before going out – it is just a way to express higher pressure buildup as the opening is no longer as large as we had it on picture (4). 
Basically, to wrap it in few words, the distance between the washer and the dish is much smaller in picture (7) than in picture (4) due to the washer’s lift (flex) restriction provided by the washer (B). In reality it is not this simple, there are many other factors that play in here. A lot could be achieved with the design of the dish, the angles of the walls, even the radius of the dish where the washer sits on top of it, etc. We are just trying to simplify all this as to get a concept and have some understanding of what is going on in some of our dampers and what are the very basic concepts behind the often mentioned “re-valving”, so we get an idea what it is, how it works, what are the very basic principles behind it. So, all those of you that have PhD in Fluid Dynamics – please be easy on me for not telling it “quiet right” – we are going through “Re-valving 101” here, and basically opening a big door, without even entering the room yet.
Next step would be to see how is the washer’s diameter, thickness, preload and quantity is decided and most important – how to modify a stack of washers in terms to modify a specific compression curve only in the areas where is needed/wanted. Next is where the real data will start coming, for our specific application.


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## pyce (Nov 7, 2001)

*Re-Valving 102 ....*

This is the kicker part. The “Shim Analysis Program” that looks on the screen like nothing fancy, but it does things that just years ago were unthinkable. Below is a screen shot at what the interface looks like. The upper and lower part is the exact same screen, but I would use the lower part of the picture as to highlight where are the points of interest for our us:








We have area A where we have to input the pre-load of the Original washers (that is provided by the 5 mm screw from the drawings in the earlier post), the internal diameter (id), etc. Then in area B we have to input the washers that are currently in the Original damper – so you can see the 22 mm washer with the cuts and its thickness of 0,15 and the other two 22 mm washers and their 0.4 thickness. This will basically provide us with what is our 100% line (what we will call “The Original Curve” – remember, we are talking only the top left part of the dynographs, the beginning of compression!). In the area C we have then the diameters, thickness and number of the new washers, that we are going to utilize as to achieve our modification. In this case we have the same exact Koni first two washers, but the top washer (which is in this case on the bottom of the list on the screen) is no longer the 22 by 0,4 from area B, but a new, smaller diameter washer – 11.4 mm by the same thickness of 0,4! So, once these data is in there, we go and look at the area D ….. The first column talks about deflection of the washer (values of deflection), the second is the “new” load needed for such deflection of the washer, the third column (blue), where it says “copy” is basically what was the Original load for the same deflection (with the old stack of washers, preload, etc) and the last on the right column tells us the difference achieved (in percentage) from the original values for every specific deflection value….. If you look carefully on that last column, as you go down (increasing the deflection) you will see how the numers stay at about 63% for few rows, then drops to about 62%, then 61% (then we run out of picture) but then it goes up again towards 62, then 63, 64 and at the end it is at around 67%. So, what we have achieved is more-or-less a decrease in value through the whole curve at an average 61 to 67%. To visualize better what is going on, there is this button on the top row of the interface, and once that button is pressed, the screen that pops out looks more or less like this:








Basically, what this shows us is that is our Original line was a flat 100% line (the green), the New compression curve would look like the yellow one. So, if we take a casual point A from the original green line that corresponds to 100%, then the new curve at that point will have 63% of its value (all these numbers coming from the percentages (from 61 to 67) we were talking about above….. Later on, we get another point from the Original curve, (point B) where the New value was reduced by 62%, so we can see that on the yellow line again. Basically, the yellow line is “shaped” according to all these percentages that are in the last column and it is a better way to see what is going on and most of all, where it is going on, which portion of the curve is affected in which way, etc. This way, later on we put those new stack of washers that the software tells us are going to provide a pretty smooth and more or less equal reduction of about 61 to 67% of our existing compression curve, and when we get the damper dynoed again, the dyno graph “should” look like this:








So, we can see how our point A went to 63% of its original value and became the new point A1 and similar thing happened to point B that is now point B1 with 62% of the Original value. What we achieved is keeping the same shape of the compression curve, but just decreased the values across the board a pretty constant way. This is basically what happened to the Koni V 1.2 that is now with about 61 to 67% of its original compression values. Those were the exact washers used, the exact diameters, etc. This whole post till this point is based on a real life experiment. 
Let’s make another scenario, so perhaps it will get clearer on how all this works. Let’s try to make the Original curve to get more of a Bilstein shape – Very steep initial compression and then flatter curve as the speed builds. We basically want a dyno curve that looks like this:








So, what we need to do now is to input new washers, with new diameters, thickness, etc that will provide us with percentages (from that last column) much higher in the initial range and lower in the final range – this way to have a new curve that is higher than the Original in the beginning and lower in the end. So, we input all the washers until the software shows us something like this:








You can see again how the relation between points C and C1, D and D1 translates from what the software shows us to the dyno graph…..
But then someone would say: “Who tells us who many washers to use and what diameter they have to be, etc?” ….. Well, that is where Phil comes to play, with his 30 years behind the “washers”







From experience he knows which daimeters provide which curves, how many washers are needed as to keep the curve rising or to “smash” it flat, how thick they have to be as to keep the flow at certain speeds, etc. That is the part where a software can’t quiet yet replace the man fully. You still need someone to “input” those numbers first and input them in the right sequence as to get you in the right direction to begin with, as the “sweet spot” (as he says) is very narrow and very easy to miss…..
Well, this is for today. More to come as we go. You all have a nice weekend.


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## Ceilidh (Jan 7, 2004)

*Re: Re-Valving 102 .... (pyce)*

I stand utterly amazed.....
No complaints yet from this former fluid dynamicist -- brilliant work and utterly clear diagrams!







(And that software was a lot of work from somebody -- is it proprietary, or can one simply purchase it from somewhere?).
Just one substantive question, and three minor ones -- 
here's the substantive one:
Q: In your earlier render, you showed the washer stack sitting entirely inside the recess, so that the bottom washer rested directly on the flat "face" of the valve seat, whereas in this latest render the washers sit atop the recess, so that the valve seat becomes the recess' lip. Are we to ignore the earlier render? (Or are there in fact two recesses -- one to form the pressure chamber & valve seat, and the other to contain the washer stack?) In any case, it's now quite clear why the tension on the washer bolt/nut has such a critical effect on low-speed damping (with the original diagram, I couldn't see how tension affected the preload; now it's quite obvious!).
(Note: I'm actually a little surprised to see the mechanism done in this particular way. With the mechanism pictured, the critical low-speed damping will be highly dependent upon how much skill and attention the assembler applies to the task of setting the preload; if he's off by a little bit, the low-speed damping will be off by a huge amount. How does Koni guard against an assembler having a bad day? Do they test every shock after assembly and then rework all the rejects? Or do they have some sort of test fixture to check the preload during assembly? In any case, it looks to be a fairly skilled-labor sort of design -- kind of old-fashioned, in a way. Could you ask Phil if KYBs etc. are similarly dependent upon the skill of the assembler? It just looks like an expensive way to do things....)
Anyway, here are the minor questions:
(1) Is the slotted washer the lowermost washer in your diagrams? (2) Is there any sort of chamfer on the lip of the recess (in effect, the "seat" on which the washer rests)? And (3) is the slotted washer allowed to freely spin, or is it held in constant angular orientation? The reason I ask is whether you notice any sort of wear on the "seat", particularly at the edges of the slots; seems like a curious design for something intended for durability -- I wonder why it doesn't cause a problem?
Great work, Peter -- keep it coming!!








- W



_Modified by Ceilidh at 12:53 AM 12-11-2004_


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## JediKGB (May 21, 2002)

*Re: Re-Valving 102 .... (Ceilidh)*

All I can say is HOLY SH!T!








I just found this thread and damn do I have a lot to read!
keep up the work http://****************.com/smile/emthup.gif 

now just to apply it all to my mk2......


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## Jezztor (Nov 9, 2002)

*Re: Re-Valving 102 .... (JediKGB)*


_Quote, originally posted by *JediKGB* »_All I can say is HOLY SH!T!








I just found this thread and damn do I have a lot to read!
keep up the work http://****************.com/smile/emthup.gif 

now just to apply it all to my mk2......

Welcome, fellow Mk2'er. You won't be disappointed


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## pyce (Nov 7, 2001)

*Re: Re-Valving 102 .... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_Q: In your earlier render, you showed the washer stack sitting entirely inside the recess, so that the bottom washer rested directly on the flat "face" of the valve seat, whereas in this latest render the washers sit atop the recess, so that the valve seat becomes the recess' lip. Are we to ignore the earlier render? (Or are there in fact two recesses -- one to form the pressure chamber & valve seat, and the other to contain the washer stack?) In any case, it's now quite clear why the tension on the washer bolt/nut has such a critical effect on low-speed damping (with the original diagram, I couldn't see how tension affected the preload; now it's quite obvious!).

A: Yes, please ignore the earlier one. That first model was very simple, just to “picture” a concept (in fact, I was very careful to write the word “concept” on the picture, as to cover my ass) , because someone may have said later that this is not really how the Konis are inside







The latter is also not quiet (not up to the actually dimensions) the real thing, but wanted to simplify it as to get the attentions on the washers and not on the body. The actual one has three steps and on the outer ring it has a lot of holes from where the oil goes from the outer tube into the inner tube during rebound. I will post a picture later, so it will get clearer.

_Quote, originally posted by *Ceilidh* »_ (Note: I'm actually a little surprised to see the mechanism done in this particular way. With the mechanism pictured, the critical low-speed damping will be highly dependent upon how much skill and attention the assembler applies to the task of setting the preload; if he's off by a little bit, the low-speed damping will be off by a huge amount. How does Koni guard against an assembler having a bad day? Do they test every shock after assembly and then rework all the rejects? Or do they have some sort of test fixture to check the preload during assembly? In any case, it looks to be a fairly skilled-labor sort of design -- kind of old-fashioned, in a way. Could you ask Phil if KYBs etc. are similarly dependent upon the skill of the assembler? It just looks like an expensive way to do things....) 

These were my exact questions to Phil when I saw how he was changing that dyno curve with a slight 1/16 of a turn on the crew (playing with the pre-load)! He said that most probably (but he is not sure) they do have some fixtures as to get to the right pre-load at all times. Perhaps you are right about the “old-fashioned way”, because Phil said this design had been around since the 70’s (may be even earlier) and Koni never changed the principle behind. The difference is (according to him) that in the 70’s this same damper was perhaps on a street Ferrari and all the car fans could only read about it in a magazine, but nowadays you can find it in a Volkswagen and everyone can buy it. As for the KYB, he said they are like on the first rendering (the “concept”) where the washers do sit directly on the disc, so pre-load is out of the equation.

_Quote, originally posted by *Ceilidh* »_ (1) Is the slotted washer the lowermost washer in your diagrams? 

Yes, it is. The “concept” dish was not like the Koni, but the washers are exactly like that – the slotted first (they call it the “bleed washer”) and then the stronger washers on top. I did a mistake in that post, saying that they are all the same thickness of 0,4 mm, but it is not true. The first washer (the slotted) is only 0,15 mm. I will go edit that part later…

_Quote, originally posted by *Ceilidh* »_ (2) Is there any sort of chamfer on the lip of the recess (in effect, the "seat" on which the washer rests)? 

It is rounded, but with a very small radius, perhaps less than 0,5 mm. I will post picture later.

_Quote, originally posted by *Ceilidh* »_ And (3) is the slotted washer allowed to freely spin, or is it held in constant angular orientation? The reason I ask is whether you notice any sort of wear on the "seat", particularly at the edges of the slots; seems like a curious design for something intended for durability -- I wonder why it doesn't cause a problem? 

Not only can spin, but can even move little bit around as the inner diameter of the washer (the hole) is bigger than the bolt that holds them together. Do not have the number on top of my head, but later will measure the washers and will tell you. What I guess, thought, is that for some reason they do not move at least in relation to each other, because on the first full washer that sits on top of the slotted you can see clear marks that contour the slots from the washer below…..I will show it later, it is pretty clear on the pictures.


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## pyce (Nov 7, 2001)

*Koni Compression Valve*

Here is the actual compression valve:









A - The holes that allow the oil to flow back in the inner tube during rebound. Did not include them in the drawings above because did not want to make it look so complicated. 
B – The 5 mm bolt that holds the washers (and responsible for the pre-load) to the disc.
C – The “slotted” (bleed) washer that that sits first on the disc.
D – The two thicker washers that sit on top of the bleed washer. Basically they would stack in the way you see them, but would be then rotated 180 degree so the slotted sits first, then the one that you see in the middle (but with the side we see facing down, facing the slotted one!) and then the last one.
E – Pretty visible on the full washer where the oil was flowing and where was not through the slotted washer! This picture is what makes me think the washers are not spinning around at all while operating.


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## Reigenhardt (Jan 31, 2003)

*Re: Koni Compression Valve (pyce)*

Was there any conclusive evidence of an OEM replacement for the rears, that will not have to be replaced every 35k?


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## alexb75 (Dec 29, 2002)

*Re: Koni Compression Valve (Reigenhardt)*


_Quote, originally posted by *Reigenhardt* »_Was there any conclusive evidence of an OEM replacement for the rears, that will not have to be replaced every 35k?

Koni Red


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## Ceilidh (Jan 7, 2004)

*Re: Koni Compression Valve (pyce)*


_Quote, originally posted by *pyce* »_Here is the actual compression valve:......


Hi Peter,
This actually looks to be a fairly clever design -- a little 1970's, as you say







, but nonetheless clever 1970's:
1) The stepped concentric rings on the bottom plate gives them the option of using much smaller diameter washers (ones small enough to sit on the inner step, instead of atop the outer step as shown) for applications requiring extremely stiff compression damping (i.e., if they need damping stiffer than can be accomplished with the normal washers, they can go to smaller ones without changing the bottom plate).
2a) Meanwhile, the initial (low-speed) damping rate can be easily stiffened or softened by reducing or increasing the number of slots on the lowermost bleed washer (i.e., currently there are 5, and there's room for 8 in this particular configuration; presumably they could also use washers with a 10/12/etc. symmetry).
2b) Moreover, the bleed slots are far enough away from each other that they more or less act independently -- you don't have to worry about strange interactions between adjacent slots, so you can simply add or subtract them at will (i.e., if you want 20% less low-speed damping than this current shock provides, you add a single additional slot).
The upshot is that the expensive-to-machine part (the bottom plate with all the holes and steps) can be used on an enormous number of different shocks (thus amortizing the parts cost over the entire product line); the parts that change from shock to shock are limited to inexpensive (and very easy to inventory) washers; and it's very easy to tailor the valving for different applications.
As for the preload (which is so sensitive to bolt tension) -- it's not the common sort of thing to do these days, from a manufacturing standpoint (the modern goal is something like what you report KYB to have done, which takes human skill and potential error out of the equation), but in a weird way it makes sense: varying the preload gives Koni an easy and infinitely variable way of adjusting the curve while using a very small number of washers. It's a little crude, and it would cause a modern quality-control planner nightmares (what with his/her worrying about the assembler having an off day), but if you're producing a huge range of shocks on a finite budget (and if you don't care about getting the nth degree of subtlety in the curve -- which is probably fine for most street applications), reducing the number of variables the R&D guys have to contend with is not a bad idea. The only thing is that it puts a premium on the assembler, but if Koni has managed to employ & train people who can consistently pull it off, why not use them?
Bottom line, from the info you've shown us, I'm kind of liking these shocks. A true expert like Phil might understandably be a little horrified by their old-fashioned simplicity (I imagine you two will soon be getting a whole lot more subtlety out of a KYB-style multi-washer stack), but for a volume production item, there are a lot of things here that make sense.
The only thing that's still puzzling me is the contact between the slotted washer and the "valve seat" on the bottom plate. Everything else here is wonderfully set up for long-term durability -- hold it, I guess I should explain what I mean about the durability....:
Unless there are more mechanical bits that we haven't seen (and assuming the rebound is handled in a similar fashion), this is an extremely durable design. There are essentially no moving parts, other than the small deflection of the washer edges that occurs as pressure is bled off, and that deflection can be kept well under the fatigue limit of the spring steel in the washer -- as a result, this valve will essentially work forever (so long as the oil stays clean). Moreover, the one contact surface (the place where metal actually moves against metal) is the (oil-immersed!) valve seat, and the load there is spread over as wide an area as possible (i.e., over the entire circumference of the washer, as opposed to being concentrated in a small point (as in a needle valve)) -- which further reduces the likelihood of wear. Thus, so long as the shaft seals don't leak and corrosive material is kept off the shaft itself, this shock should last a very long time....
Anyway, to continue: the only place where I can see potential wear problems is where the edges of the washer slots come in contact with the valve seat -- as the washer flexes up and down, the edges will rub against the seat, and if the washer can't spin, there's a chance that the edges will gradually cut into the seat. If you feel the washer can't spin (and it doesn't matter if the whole stack spins as a unit -- what matters is whether the slot edges come down in the same spot every time), and if you find that the valve seat is completely unblemished, then I'm curious as to why......
Hey Peter, could you check the edges of the slot? Are there sharp corners there, or have they rounded off the edges, so that they're blunt?
Anyway, with that one caveat about the washer slots, I can see why these shocks have a reputation for great longevity -- there's just not a whole lot here to go wrong, or to wear out over time.
Thanks for posting the pictures!!
- Ceilidh 
P.S. -- I've been told that nobody can pronounce this name. It's "KAY-lee" (like the girl's name, only this isn't), and it's a form of Celtic dance from places like Ireland and Nova Scotia. I had a lot of Cape Breton buddies when I lived in Canada, and would go with them to the ceilidh dances to meet the girls (and where sometimes the whole place would burst out into "Barrett's Privateers", which is about fighting the Americans in 1778 (the Canadians lose)); no, it has nothing to do with cars, but those were happy times....











_Modified by Ceilidh at 12:14 AM 12-14-2004_


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## 2beirish (Apr 28, 2004)

Silly, but I assumed your name was Welsh. My heritage is Welsh, Irish, and German. Heavy emphasis from me on the predominant Welsh & Irish blood. I spent a few weeks in Wales a long time ago with relatives of a dear friend. It was a total gas: travelling through the country with Trevor and Nancy. They treated me with all the wit, good manners, and grace of a family member. Lived in Abercynon, near Swansea. We sang in pubs while I was there and pubsters said "You've got pretty good pipes (voice) for an American" I was ALWAYS confused trying to figure out the difference between Soccer, Rugby, and Football.


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## Charles R (Oct 26, 2001)

*Re: Koni Compression Valve (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_
P.S. -- I've been told that nobody can pronounce this name.


Had me stumped. But then again, I'm the proud example of the 1970's american public education system.


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## Ceilidh (Jan 7, 2004)

*Re: (2beirish)*


_Quote, originally posted by *2beirish* »_....My heritage is Welsh, Irish, and German. Heavy emphasis from me on the predominant Welsh & Irish blood. I spent a few weeks in Wales a long time ago...... 

I love Wales!! Rode through there on my "pushbike" (bicycle) during University days, and found lots of towns where the older people spoke Welsh instead of English; great singers too (as you've noticed!) -- I had always thought it was just in movies that people would start singing in pubs, but the Welsh, Irish, and Cape Bretoners all do it, and they do it really well. Cool people.
Oh, well, guess I'd best get back to shocks & such, lest Peter get impatient with us.....


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## pyce (Nov 7, 2001)

*Re: Koni Compression Valve (Ceilidh)*

Hello Kay-lee









_Quote, originally posted by *Ceilidh* »_.......could you check the edges of the slot? Are there sharp corners there, or have they rounded off the edges, so that they're blunt?......

I missed that opportunity, as the washers are back in the damper that is back in the car, but I could not have given you this info anyway, as looking at the edges of something that has walls of 0,15 mm may not be so accurate. We are planning on starting with the rears now and according to Koni the design is pretty much the same, just the scale changes, so I will get one of these inside and will send it to the near by university for microscope pictures. 
For everyone else that is following here and is interested in the Yellow-to-Red conversion - I think Phil really did it, as those Front Yellows he re-valved last week had been on my car for about 4 days now (about 400 miles so far) and they do work great with the Red rears. The comfort levels are simply great, and I am slowly increasing the rebound (trip by trip) as to see what happens when we go up. So far got to 75% (Front only!) and the car still maintains very good level of comfort, which is very surprising, but true. I will try to run some accelerometer graphs this weekend, on different rebound settings, as to "show" my point......... Now the challenge is to match the rear Yellows to the Reds, but the good part is that in this case we have both dampers, so if the Yellow really does not come "easy" we can always open the Red and "copy" the amount of washers and the pre-load for the compression. The rebound looked almost the same from the dyno, so not plans to touch there, even because from how the tests are coming with the fronts - it is getting obvious that higher rebound could be ruin with little compression and this means even more comfort with not (yet) side effects like jacking-down or lifting the inner wheel in a sharp corner. More as we go....


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## pyce (Nov 7, 2001)

*The Ideal Compression Valve....*

The ideal compression valve according to Phil…….








A – Valve which you can control by hand.
B – Metal pipe.
C – Soft rubber.
D – Metal pipe
E – Compression valve with washer stack, just like the one Konis have (for example)
So, how would the ideal compression valve work? You put your hand on the lever (A) and start going left an right, therefore increasing and decreasing the opening, therefore increasing and decreasing the flow (and pressure) of the liquid that then goes through the pipe (B). Then of course it goes through the “balloon” (C) and through the next pipe (D) to finally hit the compression valve (E). The valve is closed (the washers provide enough resistance) so the pressure inside this mini-system starts building up, so the balloon (B) starts expanding and at certain point (let’s say at the point seen on the picture) the compression valve (E) opens, so no more pressure builds, this way the balloon (E) no longer grows but perhaps starts shrinking down (because the opening of E allows more liquid do go out than the liquid that comes in through A). At certain point, the pressure drops enough (we can see that from the shrunk balloon) so the compression valves (the washers E) do close (or flattens enough as to flow less liquid than what the valve A provides) so the pressure starts building again and so on…..
So, ideally, the compression valve (E) is so incredibly good at releasing pressure, that now matter how fast we change the pressure through the valve (A) and no matter how high (and how low) that pressure is – the balloon (C) has to remain slightly enlarged (let’s say as in the picture) at all time! Then we have the ideal compression control.


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## andrew1984 (Jun 24, 2002)

*Re: Koni Compression Valve (Charles R)*

Skimmed through page #5.

From what I took in, the Bilsteins respond quicker then Koni's only when they are not all full stiffness.
Would a revalved Bilstein be a better choice for motorsports rather then a revalved Koni?
The reason I ask is because it seems that the "internals" of the Bilstein are what give it the advantage of being "more responsive".


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## pyce (Nov 7, 2001)

*ansdrew...*

If the Bilstein you are talking about is Mono-Tube and the Koni you are talking about is the Twin-Tube design (precisely Bilstein Sport/HD and Koni Yellow Sport) than the Bilstein would always have an edge as it is “Victory by Design”. Winston was doing recently some very interesting calculations about how the mono-tube compare to the twin-tube (if dimensions are equal, etc). I am sure he will see this post of yours and there will be rain of formulas


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## andrew1984 (Jun 24, 2002)

*Re: ansdrew... (pyce)*

from bilsteins web site, does this make sense to you guys?

(rebound/compression)
golf 2 bilstein groupB FRONTS 300/120
race REARS 300/100

golf 1 bilstein group1race FRONTS 230/80
REARS 208/72

i cant decide if i should do bilstein race shocks, keep my koni 8610's (koni off the shelf single adj motorsport inserts) or go with koni double adj. revalved









auto/track only!


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## andrew1984 (Jun 24, 2002)

*Re: ansdrew... (andrew1984)*

found more info on Koni 8610 and 8611 Race Inserts
8610- single adj.
8611- double adj
force is in pounds(lbs)
8610- rebound 187/MAX425 , compression 187
8611- rebound 276/MAX705 , compression 176/MAX485

Test velocity done @ 13"/second
If i went with some 8611's ( or just upgraded mine to double adj.) would this be a better choice then what bilstein has to offer?










_Modified by andrew1984 at 12:47 AM 12-17-2004_


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## Ceilidh (Jan 7, 2004)

*Monotube vs. Twintube*


_Quote, originally posted by *pyce* »_If the Bilstein you are talking about is Mono-Tube and the Koni you are talking about is the Twin-Tube design (precisely Bilstein Sport/HD and Koni Yellow Sport) than the Bilstein would always have an edge as it is “Victory by Design”. Ceilidh was doing recently some very interesting calculations about how the mono-tube compare to the twin-tube (if dimensions are equal, etc). I am sure he will see this post of yours and there will be rain of formulas









Hi Folks,
Peter's asked me to post up the equations in question (although I saw the above posts, I figured nobody would want a "rain of formulas"(!) -- but if Peter wants me to post them, I'll post them







).
So, the topic is "How do Monotube and Twintube shocks differ internally in a way that influences damping control? Is one design inherently "better"?"
Before plunging into the math, we need to set the stage:
1) Although we're effectively comparing the (monotube) Bilstein HD to the (twintube) Koni Yellow (as specced for the Golf/Jetta IV), please be aware that Koni also makes monotubes for other applications. Hence they have their reasons for using twintubes on our cars, and the twintube is not (for street use) an inherently "inferior" design.
2) We're focusing on compression here, not rebound.
3) For the comparison, we're assuming the shocks behave in the manner described by the following Koni links: 
http://www.koni.com/_cars/_gen....html
http://www.koni.com/_cars/_gen....html
http://www.koni.com/_cars/_gen....html
http://www.koni.com/_cars/_gen....html
In particular, we assume the following about the compression damping:
a) In the monotube, the compression damping occurs in the piston: as the piston moves into the chamber on the compression stroke, fluid passes through the piston valving, and that passage produces the damping force.
b) In contrast, the piston passages in the twintube are unrestricted during compression, and fluid can pass through the piston without producing significant damping force. Instead, the damping occurs in the "footvalve", which controls how readily fluid can pass from the inner tube to the outer tube of the shock. (When the shock compresses, the shaft of the piston displaces fluid from the inner to the outer, and thus the footvalve imposes a damping force.)
4) And finally, there are other big differences between monotube & twintube that have a performance effect (notably temperature control and shock "fade" in hard use) that we will not discuss here.
.
With all the caveats/explanations out of the way, here's the math (Peter, if you want to throw a diagram or two into this mix, please feel free -- otherwise, the equations are going to feel pretty wearisome!):
1) Assume we have two shocks, one a monotube, the other a twin tube.
2) Both shocks have the same outer diameter, but because the twin tube has, well, twin tubes (with the piston inside the inner one), it has a smaller piston diameter. Call the monotube piston diameter "D_mono", and the twintube piston diameter "D_twin", where D_mono > D_twin.
3) For the shaft diameters, we'll use lower-case "ds" (instead of upper-case "D" for the piston), which leaves us with "ds_twin" and "ds_mono". ds_twin and ds_mono can be pretty much whatever the manufacturers want them to be, so long as ds < D.
4) Now, if both shocks are compressed the same amount "X", how much fluid passes through the compression valving in the two shocks?

Using the previously-stated assumptions, the volume of fluid is given by:

A) Monotube

Volume of fluid flowing through piston on compression stroke = Vmono:

Vmono = X * (pi/4) * ( (D_mono**2) - (ds_mono**2) )

B) Twintube

Volume of fluid flowing through footvalve on compression stroke = Vtwin

Vtwin = X * (pi/4) * (ds_twin**2)

C) Ratio of Monotube to Twintube

Ratio = Vmono / Vtwin = ((D_mono**2) - (ds_mono**2) ) / (ds_twin**2)

Example 1: suppose the monotube has a piston diameter of 5 cm and a shaft diameter of 2 cm (I'm just picking round numbers here), whilst the twintube has a smaller 4cm piston but an equal-sized shaft i.e., 2cm). Then the monotube will pass through its compression valve an amount of fluid greater than the twintube's by a factor of:

Ratio 
= ((5cm**2) - (2cm**2)) / (2cm**2)
= (25 - 4) / (4)
= 5.25

i.e., the monotube (in this example) passes 5.25 times more fluid through its compression valve than does the twintube. Note that the equation doesn't even mention the twintube piston diameter -- the twintube piston dimension has a bearing on rebound damping, but not on compression.
Anyway, we can easily change the ratio by playing with different piston and shaft diameters, but in the end the monotube will usually flow more fluid through its compression valving than will the twintube. What does this mean? Well, there's a fair bit of subtlety that Phil understands and at least I (Ceilidh) am only starting to become aware of, but in very simplistic terms, there's a relationship between the amount of fluid that flows through a shock's valving and the degree of control you can exert on the damping (e.g., if no fluid flows at all, then you have no damping and no control....). Because the monotube flows so much more fluid during the compression stroke, it's inherently more "quick-acting" (i.e., the piston doesn't have to move very far before substantial amounts of fluid start flowing through the valves) -- as a result, you get better initial turn-in upon corner entry (the shocks start working the instant the car begins to roll), and finer control of wheel & body motions, even when you've reduced wheel travel via stiffened springs. These are good qualities for racing (!), and thus people can argue that monotubes are inherently "better" than twintubes for racing use.
Two Final Notes:
1) Although the monotube looks great for competition, some of its advantage disappears for street use. A shock that reacts instantly and lets no wheel motion go undamped is also one that will tend to transmit every pebble, crack, or bump into the cabin, which some people (actually, a lot of people) find less than comfortable. Presumably a monotube shock manufacturer can tweak the valving to soften the ride/slow the action to make it more comfortable on the street, but in so doing the manufacturer will have thrown away much of the inherent "advantages" of the monotube design. Hence for daily street use, we needn't get too hung up on whether a shock is twin- or mono-tube in design; both designs can work well, and things become more a matter of execution.
2) As mentioned at the outset, we've focused on compression, but we should mention that the monotube will also flow more fluid during the rebound stroke: Equation "A" applies to both monotube and twintube during rebound, and the piston diameter in a monotube is generally bigger.
.
Anyway, Phil & Peter have some interesting things cooking (along the lines of "better execution"), and hopefully we'll hear about them over the coming weeks.
Cheers!
- Ceilidh




_Modified by Ceilidh at 10:21 AM 12-17-2004_


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## BAMA TDI (Nov 26, 2002)

Any more updates on this thread? I know it's the holidays and all but I have been keeping up with this thread since it started because I am going to need to replace the shocks and struts on my car in the near future. 
BTW, keep up the great work. 
Regards,
John


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## pyce (Nov 7, 2001)

*Re: (BAMA TDI)*

John...
As you guessed it right - vacation time!







But that is not really the reason of the pause. Phil just had an operation (which went smooth as far as I know) and will be at home for at least three weeks. The plan was to re-valve the rear Yellows to Red's compression values and see how all that works, but it is not going to happen until mid January when he goes back to the shop, so we have to be patient and wait till then. My car so far rides really nice (with the re-valved Front Yellow and original Rear Red) and this is the first time I have nothing really to complain about. Just got my butt in Vancouver (about 1.000 miles one way) and it was one of the most pleasant drives ever. The roads in Seattle are not nice and the roads here in Vancouver neither (even if it is different type of "not nice") but with the current setup I could not care less







The car is very,very comfortable, yet the higher rebound than stock gives it a very nice "sporty" feel. We can try few more dampers if anyone has desire to provide something interesting and new, but as far as I am concern - a Koni Red is what my butt needed all along. The task now is to re-valve the easily available Yellows to Red specs, so those few with similar to mine requirements can have something to enjoy. I think the Front Yellow Revalved had been working absolutely great so far and I have no doubts Phil will do the trick as easy and as successfully with the rears too. I am sure he will offer the same exact services to everyone of you who wishes to go the same route. We just need to wait till mid January for final word on the rear re-valved Yellow....... Yes, it is not a cheap route, but it is the only one I know (so far) that would give OE ride quality, with some adjust ability available and would last longer than an OE damper....... 
Happy Holidays to Everyone!..... I am going to meet Alex in few minutes!


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## BAMA TDI (Nov 26, 2002)

*Re: (pyce)*

Thanks pyce. http://****************.com/smile/emthup.gif I was getting depressed since no new info had been posted for a week.





















I can wait. 
Have a great safe vacation.






















Regards,
John


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## Occams_Razor (Jun 28, 2003)

*Re: (pyce)*

Bumping.
Can a moderator tack this to the top?
I have been following this thread with no small amount of interest but a question comes to mind.
Most of the discussion has centered around the MKIV Jetta/Golf chassis / shock combination.
I know the New Beetles share the suspension configuration but their spring rates and shocks, (I am guessing here about the shocks but since Koni and Bilstein spec a different shock, (SPORT), for the NB), are stiffer from the factory how much of this will cross over? 
I know the theory is the same. I mean the actual results... Would revalved Koni yellows to Koni Red specs also work on a NB? Would the valving have to be different taking into account their slightly stiffer stock springs?
Trying to figure out how to go on my wifes NB. Sporty but comfortable is here mantra.


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## pyce (Nov 7, 2001)

*Re: (Occams_Razor)*

Phil is doing great progress and we are getting together this Saturday to do the rears and dyno couple more dampers. It is a long weekend for me, so we will have all the time to do some major driving. I guess by the end of the weekend we would know whether he succeeded to match the rear Yellows to Reds.....
Occams - my wife also drives a NB, so her car is next. I will keep you updated. Anyway, we are both talking here a NB TDI and according the my caliper, the springs of the NB TDI are not really stronger than a let's say GTI V6, which is what I have in my Jetta....so, in a way, it the re-valved work for my car, they would work for our wife's. Also, the front and rear sway bars on my Jetta are exactly the same as the NB TDI (18 rear, 21 front), so no difference there either. Well, all we need to do is dyno the NB dampers, where I suspect some difference may arise, but it is not going to be that dramatic, I guess. nothing that you would not be able to compensate for with the Konis rebound adjustment


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## Occams_Razor (Jun 28, 2003)

*Re: (pyce)*

http://****************.com/smile/emthup.gif 
My Wifes NB is a TDI too!


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## BAMA TDI (Nov 26, 2002)

*Re: (pyce)*


_Quote, originally posted by *pyce* »_Phil is doing great progress and we are getting together this Saturday to do the rears and dyno couple more dampers. It is a long weekend for me, so we will have all the time to do some major driving. I guess by the end of the weekend we would know whether he succeeded to match the rear Yellows to Reds.....
Occams - my wife also drives a NB, so her car is next. I will keep you updated. Anyway, we are both talking here a NB TDI and according the my caliper, the springs of the NB TDI are not really stronger than a let's say GTI V6, which is what I have in my Jetta....so, in a way, it the re-valved work for my car, they would work for our wife's. Also, the front and rear sway bars on my Jetta are exactly the same as the NB TDI (18 rear, 21 front), so no difference there either. Well, all we need to do is dyno the NB dampers, where I suspect some difference may arise, but it is not going to be that dramatic, I guess. nothing that you would not be able to compensate for with the Konis rebound adjustment









Good to hear Phil is doing well. Hope you and he come up with some good stuff this weekend. http://****************.com/smile/emthup.gif








Regards,
John


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## pyce (Nov 7, 2001)

*Rear Koni Yellow Re-Valved....and few other things.*

A quick update on what is going on with our little project here..... We spent good part of the Saturday and part of the Sunday morning together with Phil in his shop and did go through several things. It is a very long story, so we will go in depth through later. Here is just briefly the highlights of the weekend:
1. First of all, Phil's knee if getting better and better, so he is now back to work and can stand and walk for several hours before the need to rest. Excellent recovery in extremely short time! 
2. On Saturday, as promised, the Koni Rear Yellow were opened and the compression valve was disassembled. This whole issue will be taken later with pictures and models, as it is very interesting and deserves a very deep talk, as what we found inside is very contradictory. In few words for tonight - Koni did a very interesting "Stack" of washers on the rear. Something that Phil calls "3 stage stack", which basically is 3 main, large washers, separated by different thickness very small diameter washers in between. It may sound already confusing, but later in the week we will go through it, as it is really interesting and it has to be discussed.....
3. Bottom line is that Phil replaced all 5 washers (left only the "bleed washer", the one with the slots on the outer side) with totally different diameter and thickness washers, put together the damper and dyno it. The impressive part was that from this very first trial we had a compression curve that matched the Koni Red compression curve like if we were to dyno the same damper twice instead of two different dampers! Amazing! Must also say that the "washer program" which we talked about few pages back, the one that suggests the washer's number, diameter, preload, etc - works like a champ! 
4. Few more times the damper came out, as we wanted to see how few other parameters would change the curve. So, we tested 10 weight oil, then 5 weight oil, then 1/8 of a turn on the preload, then 3/16 of a turn on the preload. Final setup is with 5 wt oil (like the fronts) and 3/16 turn as preload. Basically, as of last night we have Koni Reds in Koni Yellow's body!








5. Enough dyno - we go on the street. This morning bolted on the Yellow Rear re-valved (These are also V1.2 like the fronts, as the final setup ironically happen to be the 1.2 like the fronts).... So, drove around for quiet some time, all sorts of roads, etc and must say that there is a slight difference between the original Reds and these Yellow V1.2. It is very little difference, some may not even notice, the car is very comfortable, but the difference is there. At this point what I suspect is the lower rubber bushing, which on the Yellow is almost half the size, and therefore much less flexible, than the one on the Red's body. At this point, the next interesting step would be to take out the Yellow Revalved from the Yellow body and put them in the Red body and see how that rides. This experiment would definitely give us an answer of how important that rubber bushing is. I got pictures of those next to each other, but will post them during the week, so you all see the bushings. Anyway, the difference in comfort is nothing really alarming - it could be fixed with just 2 PSI less tire pressure in the rear tires. Needless to say that the re-valving could be done even softer, so to sort of overcome this physical difference between the yellow and red, but the goal for now was to match the Red's compression curve and Phil did it!
6. Finally, it was a warm day too, so I did some accelerometer runs too. As you all remember, Robert from the east coast sent me generously his Bilstein HD for the dyno and our agreement was that I would keep the damper and would bolt it on the car and do the accelerometer runs too, then return it to him. The problem was that all those runs in the past were done in sunny and warm days and since I got the HD from him had never been sunny and warm enough to resume those tests. My own observation is that cars do ride stiffer when the temps drop, so I was afraid to skew the results if the tests are done in the colder days...... so, today was warm enough to get as close as we can in January to the climate back then. Ran the accelerometer on three different dampers through the early afternoon. we now have Koni Red, Koni Yellow V1.2 and Bilstein HD. The data will be posted in the week when I get it to scale, so it could be compared correctly with the rest....... Anyway, thanks Robert, again! I will pack the damper nicely and send it to you tomorrow. It was very important to have your HD bolted on my car, because the results are something that may open a whole new discussion about the Bilsteins. Here it goes:
7. Everyone on the Vortex knows that Bilstein Sport and HD have the same valving. As of today, I am no longer very convinced about that! Some may remember I had some major issues (comfort wise) with my old Sports. I know those dampers pretty well, how they ride, what they do. Well, today for the first time I had HD on the rear and must say that the ride was quiet different than what the sports offer. The accelerometer's data would prove my words later in the week, but bottom line is that the HD felt very different than the Sports. The next very important step is to find a Sport and dyno it and run it on the car with the current setup! I would absolutely not be surprised if the Sport has significantly more aggressive valving. Time will tell, wish me luck to find one soon....
That is pretty much the weekend in few words. The details are very interesting and we will go through every one of these in depth later on.
The very important part is that we now have the "know-how" of how to convert a Koni Yellow to Koni Red and achieve OE ride quality with something that can last longer than the OE dampers, something that could be serviced, opened, cleaned, oil changed, rebuilt....... I hope some of you would benefit from this.










_Modified by pyce at 9:09 PM 1-16-2005_


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## Girlsound (Apr 27, 2002)

*Re: Rear Koni Yellow Re-Valved....and few other things. (pyce)*

I remember reading, on Biltsein's old web site, that the Sports can be as much as 15% stiffer...depending on application. This is no longer mentioned anywhere that I can find.


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## pyce (Nov 7, 2001)

*Rear Koni Yellow Re-Valved - V1.2 and V1.3*

Here are some of the results from this long weekend. The first graphs shows the curve of the new Koni Yellow Rears, re-valved to Koni Red Rear specs. It was very important to get as close as possible the initial part of the compression curve (in the top left) as all the tests so far show that part is the one that gives the most “trouble” when it comes to comfort. I spend good part of the Monday in Phil’s shop and we did several more tests, playing with just the pre-load on the washers. The pre-load mainly changes the very first part of that curve, so lots of comfort issues come from the pre-load values on the washer’s stack. But more on that later. Here is the graph of what we ended up calling V1.3, which is the final setup for Rear Koni Yellows as replacement for the Koni Red:








So, whoever of you decides to go this route – this (above) is what your dyno curve will look like. For comparisons there is also the Original Koni Yellow curve, so you can see where we started from and where we ended up.
At this point, I would say that we have finally achieved at least one of our goals – to have successful conversion of a twin-tube design damper into as-close-as-you-can-be OEM specs for at least something like a 4 cylinder Jetta Sedan! Everyone in the Bay Area and not, feel free to contact me and get a ride in my car, so to see for yourself. If interested in this conversion, please do feel free to contact Phil Douglas, the owner of “Aftershocks” in Palo Alto, CA and he will perform the same work on your Konis. You can get the contact info from his web site: http://www.aftershocks-suspension.com If nothing else, a great guy to talk to. I would recommend a visit to his shop to whoever is in the area and wishes to have some quality time and talk dampers with an expert like him. 
The nice part is that Phil can do much more than just a conversion from Yellow to Red. We some time playing with the washer program and for example, the goal this time was to get a Koni Yellow to show the exact same curve as a Bilstein HD damper! And guess what, it was piece of cake (for him). So, if anyone of you Koni Yellow owners, would like to have some sort of more “aggressive” initial valving, that could be done too. Of course, a twin tube will never perform as a mono-tube, but you can get the “character” of the Bilstein HD and transfer it on the Koni. Here is for example the V1.2, which was set to mimic the Bilstein HD. The reason I put these version names (V1.2, etc) is so if anyone wishes to get this exact characteristics, then you can call Phil and tell him exactly which Version you are interested in, so he can look in the database we are building and would know exactly how many washers, type of washers, pre-load, etc it takes to get directly to the desired version. So, here is out “HD0like” Koni Yellow:








Later on we will talk in dept about the washers we found in the Koni Yellow Rear Original, it is quiet an interesting situation


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## Ceilidh (Jan 7, 2004)

*Re: Rear Koni Yellow Re-Valved - V1.2 and V1.3 (pyce)*


_Quote, originally posted by *pyce* »_At this point, I would say that we have finally achieved at least one of our goals – to have successful conversion of a twin-tube design damper into as-close-as-you-can-be OEM specs for at least something like a 4 cylinder Jetta Sedan!


For people joining this thread midway (and who might be wondering why anyone would want to convert a Koni Yellow to OEM specs....):
.
Peter (and Phil) have apparently achieved the seemingly impossible - a shock with OEM-levels of ride comfort, but one that has:
1) Koni-levels of durability and serviceability (e.g., the shocks shouldn't wear out in 30k-40k miles the way the OEM items tend to do, and if they do eventually wear, they can be readily rebuilt)
2) the enormous Koni rebound adjustment range (2:1, meaning you can double the rebound setting in going from full-soft to full-stiff; this range is far, far larger than that of the KYB....). We'll have to wait for Peter's reports as he gets farther into this part of exploration, but it's looking like he can get a lot of handling performance with very little ride degradation, simply by playing with the rebound.
In short, Peter & Phil appear to be zeroing in on a user-tunable shock with close-to-OEM ride comfort, much-better-than-OEM handling, and much-better-than-OEM, life-of-the-car durability. Not bad, eh?








(Nice work, Peter!!!! )
- Ceilidh


_Modified by Ceilidh at 9:24 AM 1-19-2005_


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## DonL (Feb 28, 1999)

*Re: Monotube vs. Twintube (Ceilidh)*

As a relative suspension neophyte, I've been following along with great interest. My sincere thanks and appreciation to you fellas for some very interesting and great work. Just following along the discussion has given me a better understanding of the intricacies of suspension design.


_Quote, originally posted by *Ceilidh* »_... What does this mean? Well, there's a fair bit of subtlety that Phil understands and at least I (Ceilidh) am only starting to become aware of, but in very simplistic terms, there's a relationship between the amount of fluid that flows through a shock's valving and the degree of control you can exert on the damping (e.g., if no fluid flows at all, then you have no damping and no control....). 

Having been in plastics for a number of years now, I think I actually have a feel for this as well, but it's difficult to try to explain. Consider, though, that to effect a, for example, 5% change in damping, the greater flow displacement of the monotube design would allow a greater, and significantly, more accurate volume of oil for that 5% change to be effected over.
Something rattling around in my noggin: Given the properties of Newtonian and non-Newtonian fluids, what would the effect of accumulative shear stresses on the oil be when comparing the damper flow rates of the monotube and twin-tube designs? 
Would the smaller volume of metered fluid in the twin-tube, over a given piston travel, produce greater shear stresses in the oil over time? 
Would the monotube's design, requiring a greater flow volume, impart shear stresses across that total fluid volume, or are monotube designs engineered to operate at inherently lower shear stresses over the greater fluid volume?
My brain is starting to hurt. Does any of this make sense?









(BTW, Ceilidh, being a fan of the Maritimes, I knew what your SN was about. Brings back fond memories.







)


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## Ceilidh (Jan 7, 2004)

*Re: Monotube vs. Twintube (DonL)*

[WARNING: Technical geek discussion follows; most normal people will want to skip this post.







]

_Quote, originally posted by *DonL* »_Having been in plastics for a number of years now, I think I actually have a feel for this as well, but it's difficult to try to explain. Consider, though, that to effect a, for example, 5% change in damping, the greater flow displacement of the monotube design would allow a greater, and significantly, more accurate volume of oil for that 5% change to be effected over.

Hello DonL!
First of all, it's great to see someone correctly using the verb "to effect"!! (My old teacher Mr. Fitzsimmons would have been proud!)
Your argument is exactly in line with what Peter & Phil have been suggesting of late: with the monotube, you can exert finer control over the damping curve (in addition to minimizing undamped "lost motion", which we knew about already). The question then becomes "What damping curve do we really want?", which is what Peter's currently investigating -- the next few weeks/months are going to be quite interesting!

_Quote »_
Something rattling around in my noggin: Given the properties of Newtonian and non-Newtonian fluids, what would the effect of accumulative shear stresses on the oil be when comparing the damper flow rates of the monotube and twin-tube designs? 


The possibility of non-Newtonian flow caused me some involuntary shudders when I read the above, as the resulting complexities would be more than I would want to think about! But whilst the engineering plastics you work with are presumably highly non-Newtonian, is not hydraulic fluid reasonably linear? (I'm actually asking you, not raising a rhetorical point -- do you know whether hydraulic fluid is Newtonian? (This is outside my area of expertise.))

_Quote »_
Would the smaller volume of metered fluid in the twin-tube, over a given piston travel, produce greater shear stresses in the oil over time? 
Would the monotube's design, requiring a greater flow volume, impart shear stresses across that total fluid volume, or are monotube designs engineered to operate at inherently lower shear stresses over the greater fluid volume?


Anyway, assuming momentarily that the shock oil *is* non-Newtonian, I don't think you'd see much effect across the total fluid volume, as it looks like the shear strain would be concentrated in the immediate vicinity of the valving, with relatively quiescent flow elsewhere (I could be wrong on this, but the valves described above appear designed to shunt fluid radially outwards towards the cylinder walls, in a fairly uniform sheet, and mixing/turbulence should break up the flow fairly readily after contact with the walls (note also that I'm assuming fairly high Reynolds Numbers, which perhaps differs from the plastic flow you normally work with?)).
In any case, the greater flow quantities in the monotube -- quantities that indirectly scale with the area of the piston (i.e., with diameter-squared) -- are only partly compensated by the greater perimeter length of the valving, which indirectly scales with diameter. So proportionately there should be more shearing at the monotube valves than at the valves in a twin-tube. If the fluid is non-Newtonian in the normal sense (strain softening), we'd expect that to make the monotube a little softer than anticipated, relative to the twin-tube.
But again, is the shock oil actually non-Newtonian?

_Quote »_
My brain is starting to hurt. Does any of this make sense?










My brain hurts too.







Let's just pretend everything is Newtonian, and quietly carry on with our lives(!).....

_Quote »_
(BTW, Ceilidh, being a fan of the Maritimes, I knew what your SN was about. Brings back fond memories.







)

Yes, weren't the ceilidhs great? I miss the Cape Breton Step as well -- lots of Irish around here in Boston, but nothing drives like a Cape Breton reel....
- Ceilidh
.
P.S. -- Sorry about the geek digression, Peter!! We'll get back to your real thread now.











_Modified by Ceilidh at 10:43 PM 1-19-2005_


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## pyce (Nov 7, 2001)

*Rear Koni Yellow - The "voo-doo" compresison valve stack.....*

Here is a virtual model of how the Koni Yellow Rear Compression Valve looks like….. More precisely, the stack of washers, not the actual base valve. The interesting part is that we now have three “stages”, instead of only one for the front. And here is the big question – Why the front was so simple, one stage, three washers and that was it, but the rear, that is much lighter, they have done what is meant to be much stronger setup? Ok, the way this is meant to work is that the first two washers (the bleed washer and the one on top of it) are doing the main work on low and medium speeds, but then, when the speed gets higher, those two “suppose” to flex all the way up as to hit the large washer, which is the “stage 2”. That large washer is separate from the first tow by a pretty thick washer that acts like a spacer as to separate them, so they can act as “staged”. Basically, if there was no spacer-washer, the low and medium speed would be too stiff as the larger washer would act immediately, but with this small spacer-washer in between, the low speed is “softer” and only when the washer gets to flex all the way up and compensate for the spacer, then the larger washer acts and brings additional strength to the first two washers, so they slow down the flex, so less oil can go through, so the damper gets stronger at the higher speeds. If we continue increasing the speed, then all three washers flex so much up that hit the “stage 3” washer (the upper large washer), which brings additional strength, so the damper is even stronger on this very high speed….. Quiet neat idea and the principle sounds just great. Here it is:








So, I was asking Phil – why such a “complex” stack for the rears and such a simple stack for the fronts? His answer was something that my mind can not quiet digest, but here it is anyway. He believes that they are doing all this “stuff” to confuse the people who will be eventually trying to custom made later these dampers. Of course, I could not believe that they will sit down and add all these washers just so we get scared when we look at it, but he promptly proved his point. Removed the two big washers (the “staged” ones), then removed all the small washers-spacers that separate them, bolted everything back and on the dyno….. guess what? Same curve at 30.00 in/sec. Basically, his point was that the first two washers will always do the main work and in normal operation they will never flex enough to even make use of the first large washer, let alone the second one above! In theory, if you hit a super deep hole with a very high speed, then yes, perhaps all of these washer will flex and the system will (for the first time) work as designed, but at the point your car hit the hole so badly (as to get to this high damper speed and make all these washers finally work!) that you will have to worry about a lot of other things after the impact. Your front dampers, that are not “staged” will have already bottomed so badly, you would not even think about your rears. Phil thinks that, if anything, they should have done this “3 stages” stack on the front and leave the simple stack for the rears, as the front is the one that bottoms the easiest, the most, and the front is the one that needs to have very progressive valving (via stages or not), so to have pretty high value for the high speed as to prevent bottoming…… I know it does not sound right, all the things that Phil said are not really what our logic tells us, but he proved his point. He does not even expect anyone to believe all this, but in a way, all these type of “solutions” the manufacturers use for the mass production parts, is what keeps him in business


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## DonL (Feb 28, 1999)

*Re: Monotube vs. Twintube (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_... The possibility of non-Newtonian flow caused me some involuntary shudders when I read the above, as the resulting complexities would be more than I would want to think about! But whilst the engineering plastics you work with are presumably highly non-Newtonian, is not hydraulic fluid reasonably linear? (I'm actually asking you, not raising a rhetorical point -- do you know whether hydraulic fluid is Newtonian? (This is outside my area of expertise.))

You're not the only one to shudder.








Personally, I'm not sure where hydraulic fluids fall on the Newtonian/non-Newtonian scales. They certainly seem to exhibit some common non-Newtonian properties, mainly the viscosity change at elevated temperature.
(Some rhetorical free-thought typed out
However, viscosity shifts may simply be that, changes at higher temps, rather than permanent shear stress damage. OTOH, I think we've all seen clapped out hoopties bouncing down the street on wasted 20-year-old shocks. The damper oil has to have "worn out" at some point. 
Racing shocks with piggyback reservoirs are intended to allow a greater volume of oil, typically, IIRC, to try to keep temperatures under check. The high temps that would see seen in racing applications play havoc with the oil as a function of accurate and controlled damping. However, are they addressing actual shear breakdown, or simple viscosity changes as the fluid heats up.
Does a fluid that changes viscosity as it heats up non-Newtonian? I'm not technically completely sure. That's been part of my understanding of fluids, though.








quote]
Anyway, assuming momentarily that the shock oil *is* non-Newtonian, I don't think you'd see much effect across the total fluid volume, as it looks like the shear strain would be concentrated in the immediate vicinity of the valving, with relatively quiescent flow elsewhere (I could be wrong on this, but the valves described above appear designed to shunt fluid radially outwards towards the cylinder walls, in a fairly uniform sheet, and mixing/turbulence should break up the flow fairly readily after contact with the walls (note also that I'm assuming fairly high Reynolds Numbers, which perhaps differs from the plastic flow you normally work with?)).
In any case, the greater flow quantities in the monotube -- quantities that indirectly scale with the area of the piston (i.e., with diameter-squared) -- are only partly compensated by the greater perimeter length of the valving, which indirectly scales with diameter. So proportionately there should be more shearing at the monotube valves than at the valves in a twin-tube. If the fluid is non-Newtonian in the normal sense (strain softening), we'd expect that to make the monotube a little softer than anticipated, relative to the twin-tube.
But again, is the shock oil actually non-Newtonian? [/quote]
It's my "SWAG" that most damper oils are non-Newtonian, but their viscosity/shear curves would show very strong stability over both time and temperature, with the curves falling off only after extended service periods or extremely harsh conditions.
What this probably, or likely, means to this thread is that the performance curves that Pyce and Phil are generating should remain quite constant, or consistent, over a normal service life expected from the damper.
Unless this thread evolves into a racing application discussion, the ideas of Newtonian vs. non-Newtonian fluids is most likely purely academic.









_Quote »_My brain hurts too.







Let's just pretend everything is Newtonian, and quietly carry on with our lives(!)..... 
"Newtonian?" Did someone say, "Newtonian?" I didn't hear anybody say anything about "Newtonian."











> P.S. -- Sorry about the geek digression, Peter!! We'll get back to your real thread now.






> Yes, let's. There's more important things than the discussion of the viscosity changes of damping fluid.
> Like the viscosity of Guiness!


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## Ceilidh (Jan 7, 2004)

*Re: Monotube vs. Twintube (DonL)*

Hello DonL and Peter!
My last little contribution to the rheological digression.









_Quote, originally posted by *DonL* »_
......However, viscosity shifts may simply be that, changes at higher temps, rather than permanent shear stress damage. OTOH, I think we've all seen clapped out hoopties bouncing down the street on wasted 20-year-old shocks. The damper oil has to have "worn out" at some point. 
Racing shocks with piggyback reservoirs are intended to allow a greater volume of oil, typically, IIRC, to try to keep temperatures under check. The high temps that would see seen in racing applications play havoc with the oil as a function of accurate and controlled damping. However, are they addressing actual shear breakdown, or simple viscosity changes as the fluid heats up?.....


[Non-Geek; what follows applies to cars]
A very interesting point!! Peter found that when they first pulled his Koni Yellow apart, the oil inside was almost black -- presumably from hard use over many miles of concrete freeways. No idea whether that's from shear breakdown or simple high-temperature overcooking, but (reports Peter) Phil says that the shock oil is about the one thing that wears out in a Koni -- change the oil out after Xk miles, and the shock is as good as new (Peter, have I quoted you correctly?).
Also, Peter did some measurements on shock fade with temperature, which is presumably tied to viscosity drop upon heating (another area where the monotube looks better, as there's more effective convective/advective heat transfer without an "insulating" outer cylinder).

_Quote »_
Does a fluid that changes viscosity as it heats up non-Newtonian? I'm not technically completely sure.....


[Geek Alert -- everybody other than DonL, please skip!]
I've found that fluid dynamicists are no more consistent on this than are practitioners in other fields. Back in the day, I attended lots of talks on non-Newtonian flow that wound up focusing on shear-heating of an otherwise linear fluid, whereupon a crusty old theorist would get up in the Q&A session and scorch the poor speaker for not having a "real" non-Newtonian fluid (followed by much academic arguing and harrumphing). In a modelling sense, it made a difference to us only in that there were situations where we could assume the fluid was isothermal (e.g., excellent heat sinks were present and turbulent mixing would disperse the local hot spots), in which case we could use linear equations (perhaps with a local high-T, low-mu zone where the equations were still linearized, but with a lower viscosity), and feel there was still actually some hope for the universe. With a true non-Newtonian, all the equations were non-linear, nothing was solvable, the numerical solutions would go unstable, and everybody just hated life.....


_Quote »_
What this probably, or likely, means to this thread is that the performance curves that Pyce and Phil are generating should remain quite constant, or consistent, over a normal service life expected from the damper.


[Non-Geek -- applies to cars]
Yes, I think I would agree(!). Peter, did Phil give you an idea for how long it would take for the shock oil to break down? Would there be any gain to using a synthetic, if super long life was the goal? 
Cheers!
-C


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## John A (Feb 19, 2001)

*Re: Monotube vs. Twintube (Ceilidh)*

it looks like i might be finally dropping the dough on shocks in the next 4 weeks or so -- chances are i'll be going with some sort of pyce 'special sauce' setup -- will keep people filled in as things happen.


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## Occams_Razor (Jun 28, 2003)

*Re: Rear Koni Yellow - The "voo-doo" compresison valve stack..... (pyce)*


_Quote, originally posted by *pyce* »_ Phil thinks that, if anything, they should have done this “3 stages” stack on the front and leave the simple stack for the rears, as the front is the one that bottoms the easiest, the most, and the front is the one that needs to have very progressive valving (via stages or not), so to have pretty high value for the high speed as to prevent bottoming…… 

So.... Can Phil do that? Modify the Frts so they have the same 3 stage valving as the rears?


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## a4tq (Jan 18, 2004)

*Re: Rear Koni Yellow Re-Valved - V1.2 and V1.3 (pyce)*

first of all - keep up the great research and sharing of information. I'm sure I speak for many when I say its appreciated and refreshing to see such informative discussions (even if they are beyond me most of the time!)
I'm curious about the handling characteristics of a koni front revalved to the same compression characteristics as the HD. 
Under "normal" circumstances the HD appears to have a better turn in response due to its monotube design. How does the revalved koni "stack up" against the HD in track conditions? Will similar compression and rebound curves overcome any of the design differences between the two?


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## DonL (Feb 28, 1999)

*Re: Monotube vs. Twintube (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_Hello DonL and Peter!
My last little contribution to the rheological digression.









I've found that fluid dynamicists are no more consistent on this than are practitioners in other fields ... In a modelling sense, it made a difference to us only in that there were situations where we could assume the fluid was isothermal (e.g., excellent heat sinks were present and turbulent mixing would disperse the local hot spots), in which case we could use linear equations ... With a true non-Newtonian, all the equations were non-linear, nothing was solvable, the numerical solutions would go unstable, and everybody just hated life.....

Cheers!
-C 

Greetings back, and excellent post!
You're completely correct that at some point, for different types of fluid dynamic modelling, there has to be (or should be) some point of assumed consistency in the fluid, overall fluid temp, and mixing of cooler and hotter segments of the fluid. You can't model what you can't determine by ever-changing or unknown variables.
My feeling is that the hydraulic oils used in damper assemblies have excellent long-term stability and temperature range performance. For 99% of people in 99% of driving situations, from Fairbanks in January to Phoenix in August, shock absorber performance will be boringly mundane with no apparent or noticeable variation right up until the failure of the shock or long-term breakdown of the oil.
Few people have the opportunity, equipment, or talent to really beat the bejeezus out of a damping fluid. This is good for two reasons.
1) It keeps people like Phil in business rebuilding dampers with fresh oil for performance enthusiasts.
2) Directly related to this thread, the testing that Pyce and Phil are doing is completely representative of how a damper would perform over a significant time period and driving styles for the likes of all of _us_ reading this far into the thread. 
(How's that for bringing this little digression back to the topic?







)
Now, let's see some more graphs!


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## pyce (Nov 7, 2001)

*Few things...*


_Quote, originally posted by *Occams_Razor* »_So.... Can Phil do that? Modify the Frts so they have the same 3 stage valving as the rears?..... 

Sure, even you can do that! Putting washers in the damper is really not big deal.... knowing which washers to put, in which sequence and with how much pre-load (in the case of Koni Yellow which allows pre-load) - that is the trick which we do not have experience with. The bikes usually have much more complex dampers and he had showed me some sort of "ordinary" dampers for that sector (bikes) with 25, even 38 washers! but here is the thing - more washers does not mean stronger valving. Means more and more progressive valving. Strong valving could be achieved with one single washer - make it very thick, pre-load it like hell and you have it - a damper that will almost hydro-lock until you hit something very hard. Racers on flat tracks love that. I will show you tomorrow a graph from a Penske race damper, tuned for a track - basically the graph looks like a box with slightly rounded four corners







Phil tuned that one for a guy who had a special request, that his dampers are as stiff as they can get, because this is the only way he (the racer) could be fast. This is interesting story.....That guy (I actually met him one night at the shop) had to even study and modify the position in which he sits on the bike as to be able to stand the harshness (!!!) - and that is on a race smooth track! Can you imagine the stiffness of the bike! But his style is such that he has to feel every dime on the track as to be fast. They tried to soften the ride (as even he is not happy with how stiff it is!) but there was nothing to do - he was slower. The only way for him to be fast was to achieve almost no suspension travel....... So, back to your question: Yes, he can do it. He can do whatever you want. My plans are actually to get another set of used Konis and to keep experimenting. We would like to achieve more than what we have now. Stopping now is like going out with a great chick for dinner and let her go home alone after that. At this point it is pretty clear that majority of the off-the-shelf dampers for our cars are simply not fine-tuned to each of ours specific needs and there is bigger potential (which we are slowly starting to explore) for specific custom tuning. The goal here is to bring the "re-valving" to a lower level, so you do not to be a racer and you do not need to have dedicated race car as to be able to have your dampers re-valved by someone so to match your equipment. Would be nice that we have more options for the sector in between "stock" and "sport" and that is where we are working currently. I think everyone can call a Koni Rebuild Center and have theirs re-valved, the problem is that they are not really going to work with us, let alone to give you some information about dynos, curves, graphs, and so on secrets from the industry. I tried, called them time ago and the guy was nice to me till the moment I mentioned what we did with the washers - he was incredibly quick in telling that it is all wrong and that is absolutely not the way to change the compression of a damper Whoa! On the other hand, we have Phil that not only spends hours (for free!) to explain things to me and then I try to put them here, but is also proving his point every time when I simply do not believe him...... Anyway, I got carried away, sorry. Bottom line is, he will do everything that everyone of you all desire. He actually loves this type of customers the most - those that go there and say: "I want this and this and that" - so he does it and they (the customer) are responsible for the result. So, if you want "three stage" stack in the front - he will gladly do it. His point was that in the way it is designed - you do not need it. I did not believe it, he proved it to me. Can't argue data. If you want it - you will have it. He does not charge (Fortunately!!!) per washer








I wanted to write little bit more to the rest that had questions, but no time now. Will do tomorrow. Good night everyone


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## pyce (Nov 7, 2001)

*Re: Rear Koni Yellow Re-Valved - V1.2 and V1.3 (a4tq)*


_Quote, originally posted by *a4tq* »_I'm curious about the handling characteristics of a koni front revalved to the same compression characteristics as the HD.
Under "normal" circumstances the HD appears to have a better turn in response due to its monotube design. How does the revalved koni "stack up" against the HD in track conditions? Will similar compression and rebound curves overcome any of the design differences between the two?


We did only the rear, it was just to try and see as personally I am not interested in quicker- acting damper, but I am sure many here would be interested, so we wanted to see if it is doable. Anyway, here are few things that could be said..... I think we all could agree that a monotube design will always "perform" better than a tube-in-a-tube design. Or may I should say - it would be more efficient, no matter what (if everything else is equal!) as the design allows it. This thing said thought, we now have the advantage to modify our Konis, which gives us the opportunity to change those curves in a variety of ways and there will be a situation where I am sure Phil can set the compression valving in a way that the Konis could be quicker acting, at least for the turn in you are talking about. Now, careful here, this does not mean that they will be superior to the mono-tube Bilsteins, because in the exact same way a Bilstein Sport could be open, re-valved using the same crazy amount of preload and low bleed (two things that modify the quickness of acting incredibly well) and then you will have again a Bilstein superiority.... So, let's separate the answer in two:
1. If the question is: "I already have set of Koni and I would like to make them act quicker and be able to turn-in in a Bilstein-style, so I do not need to spend more money and get a set of Bilsteins" - then the question is Yes, it could be done. Note: the better comfort that the Koni Yellow provide at the moment would be gone thought! you will really have a Bilstein ride quality (but you are not going to have the mono-tube advantages).
2. If the question is: "Can a Koni Twin-Tube be set so it will perform as well as a Mono-Tube (that can also be set if needed)" - then the answer is No. But again, we are talking here a specific scenario - a turn-in reaction from a front damper.
Plus, you are talking a track condition - so it means constant go and go for laps and laps, where the twin-tube will just give up..... unless you do external tanks, cooling system and so on, but then again, the same could be done to the mono-tube as well (tricks to reduce temps) so we are back to basic.
As a said note, I would like to say that Phil has all the necessary equipment to re-valve Bilsteins as well. It is just more expansive and time consuming as you have to fill them up with high pressure gas after you are done and the caps have to be replaced each time. This is the primary reason we are working on the Konis right now, as I would like to experiment and learn as much as possible, so I need a damper that could be at least opened and closed with no expanses, faster and easier...... Later on, when we narrow the "this is what we want" I would be very interested to transfer the experiments onto mono-tube (off the shelf Bilsteins in this case, I guess) dampers.


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## pyce (Nov 7, 2001)

*Little bit more for everyone....*

*a4tq* - I just noticed you have a R32, so most of the things we are trying here will not apply directly to your ride, but the good news is that there is a gentleman (R32 owner) who already met Phil last weekend and they are making the plans for doing exactly what we are doing here on the A4 platform. I would let him to speak about his ideas, plans and goals, but just wanted to say that those R32 dampers experiments are coming and the results would be directly applicable in your case.
*DonL and Winston* - Very interesting discussion about oils here. From what I read, you two know more than the rest of us on this matter, so it would be very informative and interesting if you two decide to carry on with the conversation. I will talk to Phil about oil tomorrow morning and will then write about his thoughts. So far I can only tell that he uses two different "levels" of oil. A medium level, which is cost at about 10$ per quart for general use (the Konis we are testing are with that oil) and then he also carries Ohlins damper oil, that is 25$ per quart (!) and according to him that oil makes a lot of difference in a damper. For example, if you look at the base valve (the first post on page 8) you will notice that it is a cast part, so it is not super smooth, it is not polished. He said if you polish all those parts in a damper, it works noticeably better as the flow improves a lot plus there are lots of types of turbulences that happens at any speed of oil flow around surfaces that are not so smooth, so polishing those parts is essential (well, if we want to get anal and we are after the 0,001 sec on a race day, etc - I guess for street use it does not matter that much, even if he says you feel it!) .... So, basically he says the difference that oil brings to the table is that if we were to put it on our Konis (the 25$ Ohlins) - it would make then perform as IF they were polished inside. Then of course, if we polish the valves AND get the good oil - the results would be even greater. He was thinking that once we are done with our basic settings and set on a valving that I will use for good, then would be nice to pour the good stuff and see what that gives in our application.
*John* - I think it would be great if you decide to go this route, as you have been driving your car (if I remember correctly) on the stock dampers since ever, so by switching directly to one of the refined version we have now, will give you the opportunity to do a direct comparison with OE damper. Looking forward for your feedback!


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## alexb75 (Dec 29, 2002)

*Re: Little bit more for everyone.... (pyce)*


_Quote, originally posted by *pyce* »_*DonL and Winston* - Very interesting discussion about oils here. From what I read, you two know more than the rest of us on this matter, so it would be very informative and interesting if you two decide to carry on with the conversation. I will talk to Phil about oil tomorrow morning and will then write about his thoughts. So far I can only tell that he uses two different "levels" of oil. A medium level, which is cost at about 10$ per quart for general use (the Konis we are testing are with that oil) and then he also carries Ohlins damper oil, that is 25$ per quart (!) and according to him that oil makes a lot of difference in a damper. For example, if you look at the base valve (the first post on page 8) you will notice that it is a cast part, so it is not super smooth, it is not polished. He said if you polish all those parts in a damper, it works noticeably better as the flow improves a lot plus there are lots of types of turbulences that happens at any speed of oil flow around surfaces that are not so smooth, so polishing those parts is essential (well, if we want to get anal and we are after the 0,001 sec on a race day, etc - I guess for street use it does not matter that much, even if he says you feel it!) .... So, basically he says the difference that oil brings to the table is that if we were to put it on our Konis (the 25$ Ohlins) - it would make then perform as IF they were polished inside. Then of course, if we polish the valves AND get the good oil - the results would be even greater. He was thinking that once we are done with our basic settings and set on a valving that I will use for good, then would be nice to pour the good stuff and see what that gives in our application.



Since we are on the topic of oil, let me share an observation and also ask a question.
I have noticed on BOTH Bilstein and Koni that colder weather influences the ride *BIG TIME* the difference is HUGE, it's like the difference of a harsh ride to a firm ride. Now, I have not seen this ever before on any other stock shock/suspension system, even going through sub-zero temps.
So, since these dampers are "Sport" tuned and supposed to withstand heat and constant beating during track-sessions while not losing their damping power (and they actually do that fairly well)... could it be that the oil weight on these are much higher than stock shocks? This could possibly explain the dramatic ride difference between colder and warmer weather... am I off-base here?!


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## pyce (Nov 7, 2001)

*Re: Little bit more for everyone.... (alexb75)*

Alex, we do not know precisely what oil is in the Konis, but Phil told me it is probably in between our (USA) 5 weight and 10 weight. This is at least what he had found working on lots of Konis through the years. Anyway, your observation is absolutely correct, the dampers are very stiff in a morning and especially in cold climates it gets worse. In my climate I have to drive for about 2 miles and then I can not longer catch the difference (this fast they sort of warm-up), but in a climate like yours, I remember the ride was pretty “bumpy” long after the engine got fully warmed. It felt like they (the dampers) almost never actually got up to temperature. I am fully aware that the whole suspension group acts differently when is very cold, as the tires, rubber bushings, etc would also contribute to the firmer ride, but the oil in the dampers perhaps does the most…. Anyway, we are now using 5 wt oil in the Konis and tried 10 wt too (remember, those graphs are somewhere here?). The whole thing here is that the lower the weight of the oil – the less difference there will be between cold and hot. To make it very simple to understand, let’s use numbers, which are not actually, just to express the point – Basically, a 10 wt oil when gets hot will go to let’s say 7 wt oil, so it will lose “3”. A 5 wt oil, when gets hot will go down to only let’s say 4 wt, so it will change by only “1”. So, the lower weight you use, the less performance losses you will have between cold and hot and that is why Phil decided to go with 5 wt for our Konis. This way whatever we dyno will be the closest to everyday use later.


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## alexb75 (Dec 29, 2002)

*Re: Little bit more for everyone.... (pyce)*


_Quote, originally posted by *pyce* »_Alex, we do not know precisely what oil is in the Konis, but Phil told me it is probably in between our (USA) 5 weight and 10 weight. This is at least what he had found working on lots of Konis through the years. Anyway, your observation is absolutely correct, the dampers are very stiff in a morning and especially in cold climates it gets worse. In my climate I have to drive for about 2 miles and then I can not longer catch the difference (this fast they sort of warm-up), but in a climate like yours, I remember the ride was pretty “bumpy” long after the engine got fully warmed. It felt like they (the dampers) almost never actually got up to temperature. I am fully aware that the whole suspension group acts differently when is very cold, as the tires, rubber bushings, etc would also contribute to the firmer ride, but the oil in the dampers perhaps does the most…. Anyway, we are now using 5 wt oil in the Konis and tried 10 wt too (remember, those graphs are somewhere here?). The whole thing here is that the lower the weight of the oil – the less difference there will be between cold and hot. To make it very simple to understand, let’s use numbers, which are not actually, just to express the point – Basically, a 10 wt oil when gets hot will go to let’s say 7 wt oil, so it will lose “3”. A 5 wt oil, when gets hot will go down to only let’s say 4 wt, so it will change by only “1”. So, the lower weight you use, the less performance losses you will have between cold and hot and that is why Phil decided to go with 5 wt for our Konis. This way whatever we dyno will be the closest to everyday use later. 

Thanks for explanation. It just seems like the temp drop on these sport dampers make a much more pronounced difference than stock dampers and therefore they should somehow have heavier oil that can handle higher temps and why it changes so much from winter to summer. So, probably stock is closer to 5w and Koni/Bilstein closer to 10w.


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## Ceilidh (Jan 7, 2004)

*Re: Little bit more for everyone.... (alexb75)*

Hi Guys!
(The plows came by and I'm buried again -- just a short note before tonight's shoveling...







)
Peter and Alex, I've earlier noted your comments about the Koni temperature sensitivity, and in principle I can understand why it should happen, but in truth I really don't feel it with my car (and I'm pretty sensitive to bumps!). Between last July and two nights ago, we've had a 104 F temperature swing, and I haven't really noticed a big change in the shocks; the tires, yes; bushings, too....but if you want to hear something really curious, I've actually been using slightly softer shock settings in the wintertime (1/4 front 3/8 rear last winter; 1/8 front 1/4 rear this summer; and 1/4 front 1/4 rear starting this fall); these changes took place simply because last spring my "perfect" winter setting started feeling too harsh (so I went softer), and then this fall the "perfect" summer setting started feeling too soggy. Strange, eh?
Peter, when you first took apart the Konis, I was curious to see if there were any sort of temperature compensation mechanisms built in -- a bimetallic washer, or some other place where differential expansion or contraction would compensate for changing oil viscosity. It doesn't look like there's any such thing (at least in what you've shown us), and theoretically there should thus be a huge temperature effect, with the shocks stiffening up with cold weather exactly the way you and Alex describe....but for some reason I'm just not feeling it.
Anyway, just wanted to throw that into the data pool. I'm pretty wiped out today (had our all day grading session today, as the snowstorm closed down the university yesterday), but I'll try to address your turbulence/ non-Newtonian question later this week, once my eyes can focus again. Hope you're both having fun out there on the warm coast, and talk to you soon!
- C (W)


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## alexb75 (Dec 29, 2002)

*Re: Little bit more for everyone.... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_Hi Guys!
Peter and Alex, I've earlier noted your comments about the Koni temperature sensitivity, and in principle I can understand why it should happen, but in truth I really don't feel it with my car (and I'm pretty sensitive to bumps!). Between last July and two nights ago, we've had a 104 F temperature swing, and I haven't really noticed a big change in the shocks; the tires, yes; bushings, too....but if you want to hear something really curious, I've actually been using slightly softer shock settings in the wintertime (1/4 front 3/8 rear last winter; 1/8 front 1/4 rear this summer; and 1/4 front 1/4 rear starting this fall); these changes took place simply because last spring my "perfect" winter setting started feeling too harsh (so I went softer), and then this fall the "perfect" summer setting started feeling too soggy. Strange, eh?
Peter, when you first took apart the Konis, I was curious to see if there were any sort of temperature compensation mechanisms built in -- a bimetallic washer, or some other place where differential expansion or contraction would compensate for changing oil viscosity. It doesn't look like there's any such thing (at least in what you've shown us), and theoretically there should thus be a huge temperature effect, with the shocks stiffening up with cold weather exactly the way you and Alex describe....but for some reason I'm just not feeling it.
Anyway, just wanted to throw that into the data pool. I'm pretty wiped out today (had our all day grading session today, as the snowstorm closed down the university yesterday), but I'll try to address your turbulence/ non-Newtonian question later this week, once my eyes can focus again. Hope you're both having fun out there on the warm coast, and talk to you soon!
- C (W)

That is very interesting as the temp effect on my setup is just huge! But as you just noted you also had to make the shocks softer in winter time.
One reason I am experiencing much more variation could be the stiffer settings I have. I have 3/4-7/8 front and 3/4 rear... I think I need to take the rear down to 1/2 at least... 3/4 was perfect in summer but Peter has been in my car with 3/4 rear (in winter) and he noted immediately that rear was way too stiff... it's a little colder since then so now it's even worse!


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## pyce (Nov 7, 2001)

*Tire pressure too .....*

Winston, you drive your car with about 28/26 PSI tire pressure (If I remember correctly). My tires are at about 10 PSI above yours and that may contribute to the bigger "delta" in between cold and hot. I mean, your tires (with the lower pressure) play much larger roll in absorbing bumps, etc. than my tires that "transfer" more work on the dampers.


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## alexb75 (Dec 29, 2002)

*Re: Tire pressure too ..... (pyce)*


_Quote, originally posted by *pyce* »_Winston, you drive your car with about 28/26 PSI tire pressure (If I remember correctly). My tires are at about 10 PSI above yours and that may contribute to the bigger "delta" in between cold and hot. I mean, your tires (with the lower pressure) play much larger roll in absorbing bumps, etc. than my tires that "transfer" more work on the dampers. 

I am also at around 34PSI with max performance tires 17" wheels, so almost most of my comfort comes from those shocks!


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## Ceilidh (Jan 7, 2004)

*Re: Little bit more for everyone.... (alexb75)*


_Quote, originally posted by *alexb75* »_
....... But as you just noted you also had to make the shocks softer in winter time......

Hi Alex,
Actually, no -- I had to make them softer in the summer; in the winter they feel better an eighth turn stiffer!

_Quote, originally posted by *pyce* »_
.....you drive your car with about 28/26 PSI tire pressure (If I remember correctly). My tires are at about 10 PSI above yours and that may contribute to the bigger "delta" in between cold and hot. I mean, your tires (with the lower pressure) play much larger roll in absorbing bumps, etc. than my tires that "transfer" more work on the dampers. 


_Quote, originally posted by *alexb75* »_
I am also at around 34PSI with max performance tires 17" wheels, so almost most of my comfort comes from those shocks!


That's a very interesting point(!). In fact, that's a potentially significant data point, as it's telling us that the processes governing small-scale rapid motions are not those that control either bigger or slower bumps (Peter, could you tell us sometime about the bleeds (if any) that you find in the Koni? -- I've a feeling that the significant processes here might not be in the primary valving....).
Just got back from another 90 minutes of shoveling -- if anybody ever wonders what the "(&$)!($&!) wheel gap" is for, it's at least in part to let congealing slush spurt out sideways so that the wheel doesn't lock up solid (or worse yet, so that the fender doesn't blow out when it's packed full and you hit a bump).








Cheers, guys!


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## alexb75 (Dec 29, 2002)

*Re: Little bit more for everyone.... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_
Hi Alex,
Actually, no -- I had to make them softer in the summer; in the winter they feel better an eighth turn stiffer!


Maybe I mis-read, here's what you said:

_Quote, originally posted by *Ceilidh* »_Hi Guys!
I've actually been using slightly softer shock settings in the wintertime (1/4 front 3/8 rear last winter; 1/8 front 1/4 rear this summer; and 1/4 front 1/4 rear starting this fall); these changes took place simply because last spring my "perfect" winter setting started feeling too harsh (so I went softer), and then this fall the "perfect" summer setting started feeling too soggy. Strange, eh?
- C (W)

So, you softened the rear but stiffened the front. I really don't have much problem up front as we all know most of comfort is in the rear.


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## pyce (Nov 7, 2001)

*Race Track vs. Rally ....*

Here is a graph that represents the differences in compression values related to the displacement, needed for a Track Race Car and a Rally Race Car:









Basically we are talking about a track race car that has extremely small suspension travel and that rides on smooth-like-glass surface (almost) and a rally car that has to successfully land after a several feet jump, and remain planted on the course, plus not losing even a bolt from the impact. It is interesting to note how the track car needs incredibly steep compression curve (displacement related) which will allow light-speed reaction and would get the weight transferred the instance you touch the steering wheel! Then, of course, will also get very fast to the point where the valve will just blow open, but that point would perhaps never be reached on the track as the suspension travel is very minimal, so the car will stay in the very initial “vertical” line at all time as that little the displacement is……. Now, the rally car needs almost the exact opposite in terms to succeed. A very high value of high velocity compression and also the most progressive way to get there. This is the only way those monsters can fly that high and land, and remain planted after that. Basically the trick here is the super progressiveness those dampers give, so in few inches of suspension compression, the damper can build the resistance with the best progression it can, to the highest level of compression it can, so to practically slow down a falling car in just few inches to a point that by the end of the compression that car’s vertical motion is fully absorbed by the damper.


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## a4tq (Jan 18, 2004)

*Re: Race Track vs. Rally .... (pyce)*

One of the WRC events is known for its high and long jumps. 
Its name escapes me at the moment.....too long a day at work.
Anyhow.... during the 2004 event Seb Loeb injured his neck from a "landing" impact. I think they said they cars need to be able to withstand over 7G's when landing! A normal car would wreck its suspension on the first jump!


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## 4X4 Golf (Nov 21, 2004)

What little I have had the time to read has helped me greatly to further understand the dynamics taking place in our much overlooked "shock absorbers". Thanks for sharing your research and long hours with all of us on the Vortex Forum.


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## phatvw (Aug 29, 2001)

*Re: Race Track vs. Rally .... (a4tq)*


_Quote, originally posted by *a4tq* »_One of the WRC events is known for its high and long jumps. 
Its name escapes me at the moment....

Dakar?


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## a4tq (Jan 18, 2004)

*Re: Race Track vs. Rally .... (phatvw)*


_Quote, originally posted by *phatvw* »_
Dakar?


WRC Rally Finland . http://www.michelinsport.com/s...20WRC
The above link shows the height of some jumps. I'll leave it at that to prevent the thread going too-far off topic.


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## nogo007 (Jul 17, 2004)

*Re: Race Track vs. Rally .... (pyce)*

Folks - Not sure if anyone here will be interested, but the SAE International, in partnership with the Panoz Racing School, is scheduled to conduct a "Hands-on Racecar Suspension Set-up Seminar" with the following agenda:
o Explain the purpose and effect of each adjustable parameter
o Describe the requirements of effective racecar set-up
o Complete a full geometrical adjustment to a racecar
At the following venues:
*March 15-16, 2005*
Sebring International Raceway
Sebring, Florida
*April 11-12, 2005*
Cobo Center
Detroit, Michigan
*September 27-28, 2005*
Road Atlanta
Braselton, Georgia
For more details, head on to:
http://www.sae.org/seminarinfo
Regular fee is $1295 per attendee or $1195 for SAE members. Refer to ID# C0413
There will be additional seminars in the Detroit location concerning new developments of the Corvette Z06 from an aftermarket suspension standpoint.
-Omar
PS Hope this is not too off-topic.


_Modified by nogo007 at 12:02 AM 1-28-2005_


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## DonL (Feb 28, 1999)

*Re: Race Track vs. Rally .... (nogo007)*


_Quote, originally posted by *nogo007* »_Folks - Not sure if anyone here will be interested, but the SAE International, in partnership with the Panoz Racing School, is scheduled to conduct a "Hands-on Racecar Suspension Set-up Seminar" with the following agenda:
*April 11-12, 2005*
Cobo Center
Detroit, Michigan 

Apparently, and quite fittingly, coinciding with the huge annual SAE show.

_Quote »_
Regular fee is $1295 per attendee or $1195 for SAE members. Refer to ID# C0413


Holy crap...


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## DonL (Feb 28, 1999)

*Re: Race Track vs. Rally .... (DonL)*

Back to dampers, while perusing some older archived threads, I came across this reference link by rallypartsireland.com. It's an excellent overview of the basics and general philosophy of dampers and damper control of suspensions.
http://www.rallypartsireland.c...s.pdf


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## RichB (Jun 7, 2003)

*Re: Little bit more for everyone.... (Ceilidh)*

With the Koni adjustables on my Passat (with a bit firmer than sotck springs), I notice little difference between cold (and it has been real cold up here lately) and after driving for awhile. Having said that, with the 17's off for the winter and the 15's on (running tire pressures that are less than what I run on the 17's not to mention zero degree weather bring them down a few psi more), it is much, much harder to feel what the shocks are doing.... I could well be getting more damping from the soft sidewall 28 to 30 psi tires than from the ice cold shocks!
OTOH, on a nice spring day, with the 17 or 18 inch wheels on my GTI (neuspeed sofsports and koni adjustables), I can clearly feel the shocks loosen up and smooth out over the first mile of driving.


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## alexb75 (Dec 29, 2002)

*Re: Little bit more for everyone.... (RichB)*


_Quote, originally posted by *RichB* »_With the Koni adjustables on my Passat (with a bit firmer than sotck springs), I notice little difference between cold (and it has been real cold up here lately) and after driving for awhile. Having said that, with the 17's off for the winter and the 15's on (running tire pressures that are less than what I run on the 17's not to mention zero degree weather bring them down a few psi more), it is much, much harder to feel what the shocks are doing.... I could well be getting more damping from the soft sidewall 28 to 30 psi tires than from the ice cold shocks!
OTOH, on a nice spring day, with the 17 or 18 inch wheels on my GTI (neuspeed sofsports and koni adjustables), I can clearly feel the shocks loosen up and smooth out over the first mile of driving.


what is ur koni settin? front/rear?


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## RichB (Jun 7, 2003)

*Re: Little bit more for everyone.... (alexb75)*

On the GTI, they are set 50% front and rear. On the Passat, I think I'm about 25% rear and 35% on the front (will have to dig up my notes to be sure).


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## alexb75 (Dec 29, 2002)

*Re: Little bit more for everyone.... (RichB)*


_Quote, originally posted by *RichB* »_On the GTI, they are set 50% front and rear. On the Passat, I think I'm about 25% rear and 35% on the front (will have to dig up my notes to be sure).

IF you could that would be great. It makes a big difference.


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## koni-na (Jan 25, 2005)

*Re: Dampers (Shocks) .... little bit more about them (pyce)*

Nice equipment and good data although I just skimmed it. Some of the conclusions I do not agree with but it is mostly correct. Any additional questions conact us at [email protected]
Thanks,
Bob Noack
KONI North America Technical Staff

_Modified by koni-na at 12:49 PM 1-28-2005_


_Modified by koni-na at 1:27 PM 1-28-2005_


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## pyce (Nov 7, 2001)

*Re: Dampers (koni-na)*

koni-na .... It is very nice that you decided to chime in. I know it is asking for too much, but in my opinion, you have to spend some time and go through the thread. It will take you several hours, but I think it is essential that you realize who much we know, how much we do not know, and then you can decide which level of dialog to engage with us. We had tens of questions, maybe even more, through the development of this thread and I am pretty sure that you could answer to many of them. If you do not have the time and desire to go through this thread, let me know and I will try to go back and pull those questions out, group them and summarize them in a post, but some of them may appear very out of context and may not make lots of sense standing alone. Let me know which way you would prefer. Thanks....


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## DonL (Feb 28, 1999)

*Re: Dampers (pyce)*

I agree, Bob. If you'd take the time to read through the thread, I'm sure we'd appreciate constructive comments or corrections to misconceptions coming directly from the manufacturer.
What, specifically, don't you agree with and why? Your position would be unique in this discussion and could be a learning experience for all, even for a manufacturer learning how the public perceives ride, comfort, and performance criteria relative to the reams of marketing ad copy that's been presented to the public for so long.


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## pyce (Nov 7, 2001)

*Shim Program!*

Check this out!
I was surfing the Net in search for more info on shims and valves and accidentally found the Shim Program (http://www.shimprogram.com) about which we were talking few pages back, the one Phil uses to calculate the stack combination when re-valving! The site has a great 9 pages of “Basics” and I invite all of you to go through. It is pretty quick read and basically put in very clear a lot of things we have been trying to learn here. I wish we have found that site earlier as it would have helped understand certain things in much shorter time……. Anyway, here is the link to the “Shim Basics”, you get the 9 pages from there:
http://www.shimprogram.com/Mai...s.php
I also contacted the owner of the program (Kevin Stillwell), who promptly replied to me. Once he is done with reading our thread, he may appear here and share few things with us…..


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## RichB (Jun 7, 2003)

*Re: Little bit more for everyone.... (alexb75)*


_Quote, originally posted by *alexb75* »_
IF you could that would be great. It makes a big difference.

I'm 100% sure about the numbers for my GTI. I've done some digging around trying to recall what I did with the Passat Wagon Koni settings. Unfortunately, I did not write down what I set the Koni's on the wagon at, but after re-looking over at some related threads I had read prior to doing the install, I'm pretty confident that the numbers are 15% from full soft on the rear and around 27% to 30% from full soft on the fronts. Springs are VW Europe Passat 1BE "sport suspension" springs.
Hope this helps.


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## pyce (Nov 7, 2001)

*For Bob (koni-na)*

Bob (koni-na) ....
Let’s start from here… I would really appreciate if you could save us time and effort, so we do not need to open the Koni Reds to find out what is inside, so it would be great if you could kindly tell us:
1. What washer stack is in there (compression only) – number washers, internal and external diameter, thickness, etc. and of course, the sequence in which they are mounted?
2. Is the bleed washer the same as the Yellow, if not how many “slots” it has?
3. What is the pre-load (if there is any)?
4. I suspect the foot valve would be exactly the same (between the Yellow and Red), is that right?
5. What oil is used in the Yellow (weight wise, but brand would be great too) and what in the Red?
6. Is the oil quantity in the Red the same as the Yellow? We found the Yellow has 300 cc front and 250 cc rear – is that correct?
This all regards the dampers for a VW A4 (MkIV)
Thank you very much, this will save us a lot of time, effort and will prevent possible mistakes!
peter


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## rracerguy717 (Apr 8, 2003)

*Re: Dampers (koni-na)*


_Quote, originally posted by *koni-na* »_Nice equipment and good data although I just skimmed it. Some of the conclusions I do not agree with but it is mostly correct. Any additional questions conact us at [email protected]
Thanks,
Bob Noack
KONI North America Technical Staff

_Modified by koni-na at 12:49 PM 1-28-2005_ 
_Modified by koni-na at 1:27 PM 1-28-2005_
Bob a quick qeustion . What is the MAX spring rate that i can use with koni yellow ( sport adjustables ) Front and rear without revalving them This is for a mkiv vw 2004 GLI







Thanks Bob.G



_Modified by rracerguy717 at 6:25 PM 2-4-2005_


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## Ceilidh (Jan 7, 2004)

*Re: Tire pressure too ..... (pyce)*


_Quote, originally posted by *pyce* »_......you drive your car with about 28/26 PSI tire pressure (If I remember correctly). My tires are at about 10 PSI above yours and that may contribute to the bigger "delta" in between cold and hot. I mean, your tires (with the lower pressure) play much larger roll in absorbing bumps, etc. than my tires that "transfer" more work on the dampers. 

Hi Peter (and Alex),

I've been thinking a little about the temperature variation (it's gone up 50 degrees over the last week -- today it's 46F -- and my car's comfort is pretty much unchanged), and it might have to do with the bleeds:
Good touring tires at OEM pressures (I'm on 195/65-15 "Grand Touring" tires) will soak up the small-amplitude high-frequency stuff, as well as the initial hit on bigger sharp-edged bumps. I'm guessing therefore that, on my car, the tires are taking care of most of the bumps prior to the moment that the primary valves open. In other words, the tires absorb the small and initial impacts, and the shock valving deals with the rest.
If the above is true, the difference between my situation and yours is that your tires are sufficiently stiff that you're relying on shock movement to take care of almost everything. In practice that means you're relying on the bleeds (the openings that pass fluid before the main valve opens) to absorb the high-frequency and initial impacts: because of valve preload (which keeps the primary valves from opening right away), the shock can only move because the bleeds let fluid pass through them. In turn, these valves should show a strong temperature effect:
1) As you know, resistance to fluid flow varies directly with viscosity, and viscosity increases when the fluid gets colder. Hence in colder weather, our shock fluid is "thicker" and more resistant to flow, and all things being equal we should get a stiffer ride.
2) With the primary valving, however, there's a big self-correction effect. The valves are opened by pressure in the "chamber", and the more pressure there is, wider they open. Hence, when the fluid gets more viscous, the pressure within the shock rises -- and then the raised pressure opens the valves a bit wider. That wider opening in turn passes fluid more easily, and as a result the overall resistance to flow (the "stiffness" of the shock) doesn't increase nearly as much as we might initially expect from the thicker fluid. (There's still some effect, which leads to the shock fade you noted at high temperatures, but you need fairly big temperature swings to make it very noticeable....)
That might be why my car doesn't mind 100-degree temperature changes -- the tires soak up the small stuff, and the relatively temperature-indifferent primary valves take care of the rest.
3) The bleeds, however, are another story. Because they're just passages without any moving parts, there's no temperature correction, and stiffness (and thus ride discomfort) vary directly with viscosity. So on your car, with its stiff tires, you might be noting a big temperature effect because of the bleeds: as it gets colder, the fluid doesn't pass through them readily enough, and since the main valves haven't opened yet (and your tires aren't soaking things up), your ride gets harsh.
.
4) As for why things seem to be so incredibly sensitive: I'd need to put a scope actually into your shock to be sure (which is impossible), but it's possible you're experiencing a laminar-turbulent flow transition:
a) With (among other things) high viscosity fluid and small flow passages, flow can be laminar, meaning there's no turbulence and all the streamlines are nice and regular.
b) When (among other things) you decrease the viscosity and make the fluid thinner, however, you can cause a transition to turbulent flow, where the streamlines break up and essentially go fractal on you.
c) For reasons that aren't worth explaining in this forum (though here's a thread if you're interested:
http://gcisolutions.com/GCINotes1298.html )
When the flow in a passageway transitions to turbulence, the resistance instantly drops, by perhaps 30% or more. Or put another way, if the fluid is thick enough that you're delaying the transition to turbulence, your ride can be 30%+ stiffer than it is on a warm day when the fluid is thinner.
Given that, I'm guessing that the ambient temperatures out there on the West Coast must be just right for flipping the turbulence on and off in your shock absorber bleed valves -- on a warm day, you're turbulent and comfy, and on a slightly cooler day you're laminar and hating it.
.
5) If the above is at all true, one thing you might want to try with Phil is to get rid of the bleed valves entirely, and instead use a very soft bottom-most washer whose edge will easily deflect and take the place of the bleeds when you hit the little bumps (or on initial impact with the bigger ones). Doing so might make your shock less temperature dependent, as this "pseudo-bleed" will be partially self-compensating in the manner described in part (2). Of course, you'll have to severely limit the movement of this bottom washer so that it doesn't wipe out the bulk of your low-piston-speed force curve, but that's the sort of multi-staging that Phil is an Ace with.








.
Sorry to be so absent from the forums these days -- teaching has started up again and I've a couple of external projects going on at the same time; but I'm reading everything you're writing, so do please keep it up!!
All best, 
- Ceilidh (W)


_Modified by Ceilidh at 1:01 PM 2-5-2005_


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## dave312gti (Dec 24, 2004)

This thread has been amazing. Just the information I'm looking for.
I have Bilstein sports on my gti, and it's pretty hard to live with them on the broken and patched pavement here is Chicago. I wish more people discussed ride quality on vortex! 
I have concluded that my Sport Bilsteins have to go, and possibly replacing my 17" wheels for 16" to take some of the unbearable harshness out. I hate to get rid of the 17" (aesthetics be damned







) but I know a little more sidewall would help.
From this thread I would conclude the koni red valving is the way to go. 
However, up until reading this tread at least, I thought a possible solution would be to duplicate the suspension of the 337 / 20th Anniversary GTI. Most people say these cars handle great and ride well. They use a low pressure gas shock made by I believe Monroe (ugh, I know). Anyone have any idea what this shock is like and how it compairs to Bilstein?KYB, etc.?
The other shock I have heard good things about is the Eiback Pro sport (I have no idea who actually makes this shock). People on vortex seem to think this set up rides well. (But then again some people think Bilsteins have a nice ride, they obviously have better pavement than Chicago.
Any thoughts on the 337/20th AE shocks, and the Eiback Prosystem shocks would be appreciated.


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## rracerguy717 (Apr 8, 2003)

*Re: (dave312gti)*


_Quote, originally posted by *dave312gti* »_I have concluded that my Sport Bilsteins have to go, and possibly replacing my 17" wheels for 16" to take some of the unbearable harshness out. I hate to get rid of the 17" (aesthetics be damned







) but I know a little more sidewall would help.
Just want to comment on this . I thought the same thing but my nephew has my old 01 WE jetta 1.8T that we installed koni yellows on with APR lowering springs ( which are really intrax springs ) . At the time of install he had his winter tire setup on with the 16" bbs WE wheel with A/S michelins .The car handled better but had lots of sidewall flex and the ride was hard and bouncey. Then the other day he put his 18" on with a very small side wall and the car handles awsome and the ride is alot better .
_Quote, originally posted by *dave312gti* »_
. .Any thoughts on the 337/20th AE shocks, and the Eiback Prosystem shocks would be appreciated.
Here is alittle feed back on the 337/ 20AE/ GLI suspension . The monroe shocks/ dampners are very well matched to the spring rate .It handles DECENT untill pushed then its just riding off the bump stops .IMO its way under sprung ( spring rate ) for someone that wants awsome handling when pushed . I think the best way to get the best of both worlds is to go with a koni yellow sports valved spec for what spring rate your looking for . If you want something without going through all this get the vr-6 kit on the 1.8T ( the front springs are about 60 -80lbs stiffer ) and the spring i beleive is 50 mm shorter / lower, this is for there coilover setup . Hope this helps







Bob.G

_Modified by rracerguy717 at 3:26 PM 2-7-2005_


_Modified by rracerguy717 at 3:27 PM 2-7-2005_


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## RichB (Jun 7, 2003)

*Re: (rracerguy717)*

I'd like to echo the comments that racerguy makes above in regards to the 20AE suspension.
dave123gti, I was on my way to going with a 20AE spring based suspension system, but after doing much, much research/reading here I decided on a different set-up that is working out very well for me. First was the Koni Yellow Adjustable shocks which were then mated up to the Nuespeed sofsport springs. The looks/appearance is very 20AE like, but the rates are higher (actually progressive and start off just a little bit stiffer than the stock sport suspension springs) and the Koni's really allow one to dial in the comfort level. The ride of this set-up on my 17"s is quite comfortable and smooth even though I am running the Koni's at 50% (though I would imagine for Chicago area roads you would probably dial that down to 15% to 30%). The adjustability of the Koni's is the key here as I also have them on my Passat wagon (with Euro VW sport springs) set at the softer end of thier adjustment range and the ride is firm but very comfy even on the occasions when I have to drive in and around the NYC metro area.


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## dave312gti (Dec 24, 2004)

thanks RichM and Bob G. for the feedback and info. I've used Koni reds before with stock springs and loved the results (fiat 124 and older vw) but was a little cautious about the stiffer yellow koni model. These things aren't cheap and buying them twice is a little painful! At least if I buy the koni yellows there is the option of revalving if they are still too harsh.
I thought I'd get a more compliant compliant shock installed and see how the 17" wheels feel then. (I do love the looks and light weight of my oz volcanos). My 3 series driving friend insists on going to 16", because he did the same thing, his 17" wheels where pounding him pretty good. 
thanks and I'll keep you posted, 
Dave


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## a4tq (Jan 18, 2004)

*Re: (dave312gti)*

(I know the thread is geared more towards MKIV's but I still wanted to share my experiences in the spirit of information exchange!)
Last night I replaced the rear shocks on my R32 with koni yellows set to 1 full turn. I'm assuming this is approx 66% stiffness as the range of motion appears to be just over 1.5 turns.
The initial impression is that the koni yellow has much better control than stock. The rear of the car feels more connected (or less floaty depending on perspective) over undulating stretches of roadway. The ride is slightly firmer than stock, but not so much that comfort is negatively impacted.
This weekend I hope to be able to run some timed laps on a private road course used by a nearby police academy. It will be an interesting experiment as I've ran the course many times before in stock trim and will be able to compare the two setups in a reasonably controlled environment.

I'll post results after the weekend.


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## pyce (Nov 7, 2001)

*The OE Sachs Damper (rear)*

Last night finally got the time to cut the OE Sachs rear damper (VW A4). Have no idea which car this damper came from exactly, but it is some sort of a Jetta. Will find that out later via the part number, but for the moment it is not so important.
Very interesting to see that this OE damper is very “close” to the Koni Yellow. They both use the same “principle”, meaning there are washers involved, there is a casted piece of valve which overall shape looks like the one Koni has. The holes configuration and various sections are quiet different, but my point is that if I put Konis foot valve on the OE tube, it may actually work quiet well (with some revalving, of course, as the flow’s quantity is clearly different). The piston looks strikingly similar too, it operates in the same way, just addresses some of the issues in a different way, but that will be a long discussion later….. Here is a picture of the Compression Valve (Foot Valve):








1. – Return Spring
2. – Return Washer
3. – Flow Capacity Washer
4. – Base Valve
5. – Compression Washers
6. – Rivet
Yes, the who assembly is held by a rivet which we had to cut as to take all this apart. If you all remember, Koni has a screw in there. Clever thought, nail everything together and bam! – rivet it! There is some slight pre-load on those washers too, will measure it later on. But the base valve is designed in a way that the pre-load is determined by a rib below the washers, so it is not something to worry about during assembly. I will post detailed picture of the base valve later on. So, in more details:
The Return Spring (#1) basically stays there (you could see on the lower picture who the #1, #2 and #3 sit on the base valve (#4) - this is how you would see it if you were looking from the inside of the tube.) to push the Return Washer (#2) on top of the valve, so to ensure only one way flow. This is – then the piston goes up (rebound) the oil from the outer tube has to flow into the inner tube. So, the spring is pretty weak and allows the washer (#2) to lift and flow through the foot valve. During compression thought, the flow pushes on top of the washer and presses it on the foot valve, so the flow goes only through the holes in the middle. The small Flow Capacity Washer (#3) is there to actually partially cover those holes in the middle of the foot valve, so to control the speed of the jets. This could be a very long conversation as Phil was talking to me last night about the importance of the jet’s speed, the geometry (where are they positioned) and the section of the holes, etc. It is an entirely different subject, but I am sure some of you will find it very interesting, so we will talk about it later. Anyway, to make it short, that small little washer is a very clever way to address the high speed compression, this way to basically make sure the damper is soft and nice on low speeds (for comfort) and then has a pretty strong high speed when needed. On the other side (which you do not see so well on the above picture as the base valve (#4) came in dark, but I will post it zoomed-in later) basically we have the 6 washers (those are 15,5 mm outer diameter, 6 mm inner diameter and 0,15 mm thickness) all the same! No bleed, no variable thickness, no variable diameter! Pretty soft combo, but because of the Flow Washer (#3) works great on the high speed, so we have some sort of “benefit from both worlds”. It may not look so clear for now, but the base valve more detailed pictures are coming, so it will start make more sense later today.
In general, to conclude this first touch with the OE Sachs damper, according to Phil this damper is quiet a high quality unit and it has more modern and “sophisticated” solutions than the Koni Yellow! Yes, I do realize no one here would believe so, but those were his words when looking at it. According to him, the only reason (beside some sort of mechanical failure due to broken parts inside) those dampers go bad is because the oil gets old, as all the parts inside looked to him like very well designed and executed pieces. I do not know how old this particular damper was, but the oil looked pretty clean (much better than the one that came from the Konis) and it was red in color. Also, looked like low weight, pretty watery if I could say in this way. There were no signs of abnormal wear, scratches, etc. He thinks that if we find a way to service these dampers, like replace the oil and refill with nitrogen every let’s say 30.000 miles – there dampers will last very long time.
More later….


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## Ceilidh (Jan 7, 2004)

*Re: The OE Sachs Damper (pyce)*

Hi Peter,
I'm having a little trouble seeing the geometry of the flow control washer -- when you have a chance, could you possibly post one of your usual fantastic Solidworks section views? It'd be nice to see how it's oriented relative to the various ports. Thanks very much!
- C (W)


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## pyce (Nov 7, 2001)

*The OE Sachs Damper - The Foot Valve*

Here is a closer look at the foot valve. It is interesting to note that the overall surface is noticeably smoother than the foot valve in the Koni Yellow. Also, as could be seen from the section (not in scale, just trying to visualize few points here), the edge where the washer touches (from where the oil flows once the pressure increases) is very well rounded! It is also very visible how they have resolved the pre-load consistency – the inner “boss” is part of the casting, so no matter what, the washers in all assemblies will have the same pre-load when the rivet goes in. Interesting to note that there is no bleed-washer in this assembly. That is, the first washer that sits on the foot valve (in red on the picture) is a full washer, no slots like we had in the Koni Yellow (this last fact has nothing to do with the picture above, but I think I forgot to mention it earlier).








Winston, give me some time and I will try to model something. It is a very interesting concept (how they approach the high speed with obstructing the holes!) and it deserves some modeling!


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## GeWilli (Oct 3, 2000)

peter,
if you were a NASCAR fan you'd have seen the indepth 'specialty' TV spots on the suspension.
Its all the same and the smallest smallest amount of difference in the shim will make a few tenths on the lap times...
anyway - i guess having taken apart numerous "Judy" dampers (not one of Rock Shocks better ideas) also helps my POV...
Its all very cool though - makes me wanna take apart the OE Stock TDI Golf dampers and compare them to the OE GTI 'Sport' upgrade dampers i think i still have laying around...
good stuff peter good stuff


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## pyce (Nov 7, 2001)

*OE Sachs Damper - Flow Control Washer ....*

Here is an attempt to visualize what happened when different size of Flow Control Washer is applied at the entrance of the foot valve. Now, want to make a point here, this whole name of it (Flow Control Washer) was pure invention as I have no idea how would such a washer be described, so if there is a better name and some of you know it, let us know to correct it here. I guess the most accurate name would “Jet High Pressure Control Washer” but let’s keep it this way till Winston comes and tell us that the latter is more correct







Here are the three scenarios. 
A – no washer at all (like for example in the Koni Yellow application)
B – small washer that covers less than half of the hole’s diameter (like in the rear OE Sachs damper)
C – bigger washer (wider diameter) that will help tweak the high-speed, to make it different than “B”, but without changing the low and mid speed.









It is a long write up, perhaps with some additional sketching that had to be made, so it is not going to happen tonight, but perhaps we will work on this tomorrow morning.


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## Ceilidh (Jan 7, 2004)

*Re: OE Sachs Damper - Flow Control Washer .... (pyce)*

Hello Peter,
Regarding that nicely radiused valve seat: look familiar at all?








- W
P.S. -- Peter, "flow control washer" is probably the best name for it; technically it appears to be a sort of "high-flow port constrictor", but that's too balky a name....
Regarding its operation: did you say that the main stack washers are very light and flexible? And is Phil very approving of it? It looks like its function is to freely pass fluid on to the stack washers at low flow rates, but to progressively take over the damping function as the flow rates increase. The thing I don't quite get is where the transition point occurs: if the transition is at low enough flow velocities, you'd have an extremely "progressive" (damping rate rising strongly with flow velocity) shock, vs. the "digressive" (pressure blowoff at high velocities) curve that Bilstein et al tout. But if the transition occurs near the top of the shock's effective operating range, then I guess it gives a nice progressive ceiling to the damping curve....
Peter, next time you're at the shop with a ruler in hand, could you please take a few measurements for me? Specifically, could you post up the diameter of the valve seat (or washer diameter, if that's easier); the maximum deflection of the washer edge (a ballpark estimate from Phil would do); the diameter of the 6 footvalve ports, and the amount of constriction caused by the FCW? If we have those numbers, we'll be able to roughly see when and if the FCW comes into play...
Thanks again!


_Modified by Ceilidh at 12:02 AM 2-18-2005_


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## pyce (Nov 7, 2001)

*Re: OE Sachs Damper - Flow Control Washer .... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_ ….Regarding that nicely radiused valve seat: look familiar at all?









Sure it does!







Guess the ultimate foot valve will carry your name one day!

_Quote, originally posted by *Ceilidh* »_ Regarding its operation: did you say that the main stack washers are very light and flexible? And is Phil very approving of it? 


_Quote, originally posted by *Ceilidh* »_ ….. next time you're at the shop with a ruler in hand, could you please take a few measurements for me? Specifically, could you post up the diameter of the valve seat (or washer diameter, if that's easier); the maximum deflection of the washer edge (a ballpark estimate from Phil would do); the diameter of the 6 footvalve ports, and the amount of constriction caused by the FCW? If we have those numbers, we'll be able to roughly see when and if the FCW comes into play... 

The parts are actually here with me. I have the whole damper in pieces, except the outer body. Later today I will take the measurements you need, but right now can tell you that the washers are very soft (0.15 mm thickness only!) even if they are six. If the information I got is correct, it takes 8 washers of this thickness (0,15) to equal one single washer with 0,30 thickness! The formula I found is this:
(A / B)^3 = C
A – The thickness of the thicker washer (in mm)
B – The thickness of the thinner washer (in mm)
C – The number of “A” washers needed to equal the effect from one “B” washer
So, we have (0.30 / 0.15)^3 = 8
More later.


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## pyce (Nov 7, 2001)

*OE Sachs Damper - Foot Valve*

Just finished the Foot Valve.... will provide all requested dimensions in the next hour or so....


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## pyce (Nov 7, 2001)

*OE Sachs Damper - Flow Section*

Winston, here is the Flow Section. I know you can calculate it, but the software gives it for free, so why not use it .... I will see Phil tonight and will ask him about washer deflection. Tell me what else do you need....


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## pyce (Nov 7, 2001)

*OE Sachs Damper - Foot Valve Section*

Winston, here are some of the dimensions you may need. Let me know if more is needed.... Everything is in millimeters, let me know if you need it in inches.
edited to add - Note the flow holes are each opposite couple different diameter, but positioned in a way that the most inner part of each hole (if you look from top) is "touching" a virtual circle with same diameter for all of them!










_Modified by pyce at 6:02 PM 2-18-2005_


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## Ceilidh (Jan 7, 2004)

*Re: OE Sachs Damper - Foot Valve Section (pyce)*


_Quote, originally posted by *pyce* »_.....here are some of the dimensions you may need. Let me know if more is needed.... Everything is in millimeters, let me know if you need it in inches.
edited to add - Note the flow holes are each opposite couple different diameter, but positioned in a way that the most inner part of each hole (if you look from top) is "touching" a virtual circle with same diameter for all of them!........

Peter, this is great!! Don't knock yourself out getting further information; the valve lift would be nice, but already you've provided enough to show the basic idea of what's happening (at least as far as I can tell, though I'm sure Phil could add quite a bit more







).
1) First of all, you're an awesome (and awesomely fast) Solidworks jockey!! Do you work in ProE as well? We could definitely have used you on the last robotics project I was on, before going back to academia. Seriously, your employer is lucky to have you!
2) As to the valving -- I didn't realize (though in hindsight, your original photograph clearly shows it) that the holes are multi-sized. The arrangement is pretty neat: it provides a subtle and elegant way of controlling the high-speed flow, though working out the correct sizing for a smooth curve must have taken a little while(!). Here's my understanding of how it must be behaving; please tell me if it matches up with what you heard from Phil:
a) On the Koni, the bypass holes/ports in the foot valve do not apply any restriction to the flow; they exist solely to allow fluid to freely pass to the washer stack & bleeds, and it is the washer stack that takes care of all the damping.
b) On the Boge, the fewer and much smaller ports still freely pass fluid to the washer stack at low flow velocities -- they can do so because at small washer/valve openings, the flow resistance caused by the washers is much greater than the resistance associated with flow through the ports. In this regime, the damping curve is entirely created by the characteristics of the washer stack.
c) At higher flow velocities, however, the soft washer stack opens so far that it can pass more flow than can be comfortably admitted by the ports. In this regime, the damping curve becomes essentially parabolic, with damping force increasing with the square of piston velocity (in keeping with the velocity-squared resistance of flow in a simple port)>
d) Points "a" through "c" we knew about yesterday. What's new here, however, are the varying sizes of the ports, and the manner in which the "Flow Control Washer" obscures their opening. These new characteristics provide a gradual, "staged" transition from pure washer/stack flow to pure port flow.
e) Specifically, as flow rates increase with rising piston speed and larger washer stack openings, the ports don't all "top off" at the same time. The little ones saturate first; then the middle ones; then the big ones.
f) The crescent-shaped openings caused by the FCW further contributes to the staged nature, as in effect the points of the crescent saturate before the mid-section.
g) As a result, there's a pronounced period of high-velocity flow during which the damping curve is partly controlled by the saturated ports, and partly by the washer stack. Through playing with this interaction, and through bringing in the port-controlled flow in a progressive and staged fashion, it's apparently possible to create a very smooth and linear high-speed compression curve (which, if I understand you correctly, is what Phil finds desirable).
3) The question from me, however, concerns why the above is necessary. Has Phil said anything about this? It seems that if a thick washer stack can accomplish any curve, then there should be no need to play such games with the bypass ports. Or are there some curves that are hard to achieve with washer stacks alone?
Hmmmm. It looks like Boge is relying on an extremely soft washer stack to give a really soft "nose" to the damping curve, to the extent that bleeds are not even necessary (in the Koni, there has to be a bleed because the stiff washer and substantial preload will prevent the valve from flowing at low piston forces; here, presumably, the washer stack will flex even for very gentle ride motions). If I had to guess further, I'd conjecture that in order to get good flow rates through the valve at these low piston speeds and forces, Boge is deliberately using a small-diameter washer stack (which effectively concentrates the flow through the valve); perhaps this small-diameter stack precludes the easy high-velocity stiffening you get with a taller, larger-diameter stack, and perhaps it becomes easier to control the high-velocity flow with the ports....? 
Interesting: rather than use bleeds to control the lowest-speed flow and the valve stack to damp everything else (as seen on the Koni), Boge appears to be optimizing the valve-stack for lowest-through-medium flow rates, and the ports for the high-speed.....
Anyway Peter, thanks again for all the work displaying everything! Please keep us posted, and whenever you can, I'd love to hear your/Phil's thoughts on the Boge philosophy. All the best!
- C (W)


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## pyce (Nov 7, 2001)

*Front OE Sachs Damper - Compression and Rebound....*

This is damper-pornography here! 
Ladies and Gents - the Front OE Sachs Valving (Compression and Rebound)....... 








I have no time to give the details now, because it is really long description how it works, but want to say only that the OE stuff is not "crap" at all! It is actually the smartest design we have seen so far, it is just set so it si soft for comfort, but if this damper gets re-valved - it is going to be a real champ! This was also the first time I saw Phil get actually excited about car dampers, because the stuff Sachs put inside is very high end (concept wise, I do not know about materials). This damper deserves a thread of it's own as a lot of modeling will be required as to visualize some of the features it has in the design. Have to go now, but here you have it, piece by piece, so some of you (puzzle lovers







) could spend the the cold weekend trying to solve it. It is a piece of art. Kudos to the designer/engineer behind it! http://****************.com/smile/emthup.gif


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## Ceilidh (Jan 7, 2004)

*Re: Front OE Sachs Damper - Compression and Rebound.... (pyce)*

Hello Peter!
I'd like to take you up on your challenge







, but first let me make sure I'm seeing what's really there. Can you confirm that:
1) The top row of washers is the rebound stack laid out from bottom washer to top washer, with some sort of strange bleed/chamber/cloverleaf washer arrangement at the bottom....
2) The leftmost three objects in the second row is a compression mid-valve on the piston....
3) The two objects in the middle of the second row are some sort of hold-down for the rebound stack(?????).....
4) The rightmost object in the second row is the mount for the rebound stack....
5) The 3rd and 4th rows together lay out all the parts of the compression footvalve, with the coil spring at the bottom of the stack, and the washer series (row 4) inserted between the silvery 4-pronged tab washer and the complex footvalve housing.
Is the above correct?
6) And could you also confirm that most of the washers have small castellated nubs on the outside periphery (that presumably fit into some sort of recesses somewhere) so that they are not free to spin? And if so, the strange 3-pronged tab washer sits so that the tabs cover the 3 holes in the housing?
Anyway, if that's the correct geometry, I'll try to take a pass at what it's all doing -- but you're right, it's kind of hard to visualize without seeing it assembled in 3-D. Neat stuff though -- looking forward to learning more!
- W


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## Ceilidh (Jan 7, 2004)

*Re: Front OE Sachs Damper - Compression and Rebound.... (pyce)*


_Quote, originally posted by *pyce* »_......the Front OE Sachs Valving (Compression and Rebound)....... 
........is actually the smartest design we have seen so far, it is just set so it si soft for comfort, but if this damper gets re-valved - it is going to be a real champ! This was also the first time I saw Phil get actually excited about car dampers, because the stuff Sachs put inside is very high end (concept wise, I do not know about materials)........ 

Hello again, Peter,
Ok, I'm going to stick my neck out (though safely so, since I can always claim (if I'm completely wrong) that I really couldn't make out the mechanism from the photograph







):
I don't actually claim to see it in the photo you posted, as I still can't sort through what sits on top of what, but if this is a mechanism neither of you have ever seen before, and if there seems to be an extra set of springs and washers (in addition to the non-return valving) that seems to sit there in addition to the ordinary valve stacks, then I'm going to guess that this shock has some form of inertial bypass valving.
That is, if the assembled mechanism has some sort of mechanical mass attached to a washer and a spring, then a possible role for the mechanism is to open additional bypass valves under impact (sharp bump) loading.
The principle here would be that:
Upon a sudden upward movement of the valve assembly (corresponding to a sudden jolt upwards when the wheel hits a bump), the inertia of the mechanism compresses the coil spring and uncovers an additional series of holes, which by allowing fluid to pass freely through the valve, prevents transmission of shock into the cabin.
Is that anywhere close to what you see? 
- W


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## nogo007 (Jul 17, 2004)

*Re: Front OE Sachs Damper - Compression and Rebound.... (pyce)*

Note sure if anyone would have the information, but:
As far as the OE dampers are concerned, does VW always use the Boge/Sachs parts or are Monroe dampers also used on occasion? Additionally, the premature failures on the rear dampers is on which make of dampers - Monroe or the Boge/Sachs; and what causes the failure, just an oil leak or some other design flaw? By premature failure, I mean when people swap out their stockies at 30,000 km or so, the rears are usually shot.
Maybe someone should give Pyce some Sachs dampers from the Autotech ClubSport kit to "test"
Great work folks - keep it up.
--Omar


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## placenta (Jun 3, 2003)

you two guys (celia and pyce) are so insanely deep into this crap.. its time you started your own shock company and made me some perfect shocks.


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## pyce (Nov 7, 2001)

*Re: Front OE Sachs Damper - Compression and Rebound.... (Ceilidh)*

Winston..... I am sorry for the poor quality picture! Now that I am looking again at what you see from it, it is very unfair to ask you or anyone else to even think about how this work. The shot at the foot valve gives absolutely no idea about the shapes inside and without that everything is pure guess.What you see is very misleading, but I really did not have time for details today........ Anyway, the whole pleasure of this thing here is to figure it out by yourself, so I am not going to take away that pleasure from you or anyone else







Just wait till tomorrow and I will give you some perspective views of the foot valve, plus will put some washers inside, so you see before and after, and I am sure it will be easy to go from there...... This thing here was like showing you a top view of a piston, asking you to guess what's the distance between the piston rings







Sorry!
nogo007 - According to Phil, there is really nothing to wear much inside those Sachs/Boge dampers. The parts do actually look pretty good to him, and definitely not worse than what we have seen in the Koni Yellow! What really happens is that the oil "wears out" for those 20-40K miles and needs to be changed, but it could not because the damper is not serviceable easily. Anyway, one of the small projects now will be to take one of those old dampers I got and make a hole, take out the oil, put new oil, charge again with nitrogen and dyno it before and after, so we see if it is really just the oil......


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## ruking (Apr 4, 2003)

*Re: Front OE Sachs Damper - Compression and Rebound.... (pyce)*

Hmmm. Does this get down to a conventional strut vs synthetic shock oil debate?








More seriously, it would appear that slight manufacturing changes to make nitrogen and oil changes easier could change struts and shocks from disposable items into longer wear items.



_Modified by ruking at 7:21 AM 2-20-2005_


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## pyce (Nov 7, 2001)

*Front OE Sachs Damper - Compression Valve*

Here we have some perspectives and a sequence that would show better the relation among the parts. There is a thin red line that describes the section on pix #1, let me know if too difficult to see it and I will make it larger.......
The sad part is that yesterday I thought this is piece of art because I was thinking it works in certain way, but this morning discovered that it does not work that way! It actually works in a more conventional way....... I will share that other idea later. Meanwhile, here are the pix (sorry, bad quality, but no time to do better job):


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## Brocken (Dec 29, 2004)

I tried reading a lot of the info but it went way over my head.
Can somebody answer a question for me?
What would be the best damper for an improvement in handling but keep a close to stock ride(actually stock it's a little choppy sometimes)? Basically I want to improve my handling but I like having a more "luxury" ride. I know there's gotta be something that gives you one without comprimising too much of the other.
thanks


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## Back2Dubs (Apr 15, 2004)

*Re: (a4tq)*

This is really interesting as I have the same setup right now that you do (KONI rear dampers set to 1 full turn with stock fronts). I ran the car for the first time at Thunderhill raceway on Saturday with this setup. Here is my post:
http://forums.vwvortex.com/zerothread?id=1843636
I agree exactly with what you have written here and confirmed it on the track with these excellent dampeners http://****************.com/smile/emthup.gif 
Sorry if this is a bit 'off topic', Peter, but I got excited that someone was actually running the same setup that I am on my R32 and can confirm what I have experienced so far=) 


_Modified by Back2Dubs at 5:55 AM 2-22-2005_


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## pyce (Nov 7, 2001)

*Re: (Brocken)*


_Quote, originally posted by *Brocken* »_...What would be the best damper for an improvement in handling but keep a close to stock ride(actually stock it's a little choppy sometimes)? Basically I want to improve my handling but I like having a more "luxury" ride. I know there's gotta be something that gives you one without comprimising too much of the other.
thanks

The answer starts here:
http://forums.vwvortex.com/zer...77940
After reading that post, go to the bottom of the page and read the last one, then to the next page for more. Koni Red is the only damper that I have tried and that meets your requirement. The good news is that KONI is going to bring it to the USA market in few months (at least representative from KONI said so). You can either wait and get those, or if you can not wait - there is always the opportunity to get used Yellows and revalve them to Red specs. This second option may end up being more expansive, but you gain front damper external digestibility that is not available with the Reds.


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## The Kilted Yaksman (Oct 31, 2000)

*Re: (pyce)*

Can we get confirmation from the Koni guy that has posted in this thread before? I would put off my purchase of KYB AGXs if I could get Koni Reds in the near future.


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## pyce (Nov 7, 2001)

*Re: (The Kilted Yaksman)*


_Quote, originally posted by *The Kilted Yaksman* »_Can we get confirmation from the Koni guy that has posted in this thread before?......

This is his only reply:
http://forums.vwvortex.com/zer...56432
You get the e-mail from there. He is very nice and will reply to you promptly. He mentioned the Red's coming to N.A. in another thread, do a search with his user name and you will find it.
edited to add....... here is the thred in question:
http://forums.vwvortex.com/zerothread?id=1802644


_Modified by pyce at 11:38 AM 2-22-2005_


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## pyce (Nov 7, 2001)

*Inside The Foot Valve (Sachs OE Front)*

Here is how does the Foot Valve looks like in section. This is only the internal part, did not build the exterior as not to confuse for the moment. Later today will try to build some of the washers and the parts that are necessary, so the model is easy to understand....


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## pyce (Nov 7, 2001)

*Inside The Foot Valve (Sachs OE Front) - Part II*

This is the section with all the relevant components in their place….








Below are the real parts, with the same numbers, so it is clearer which part goes where in the section above..


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## Ceilidh (Jan 7, 2004)

*Re: Inside The Foot Valve (Sachs OE Front) - Part II (pyce)*

Hello Peter,
You're right. This mechanism is, um, interesting....








I'm afraid I'm still having trouble getting my bearings on it: may I please ask you for one more sketch? Could you please briefly lay out (a simple 2-D not-to-scale diagram would do) how and where this valve sits in the overall shock? At the moment I'm not even sure where this valve sits relative to the inner cylinder, the outer cylinder, or the piston (e.g., Does the piston shaft pass through the inner hole, or is that where the rivet goes? During compression, is the fluid passing down through the valve, or upwards through it? Where is the connection to the outer cylinder? Etc., etc.....)
In any case, it certainly does look strange -- can you confirm that the bottom-most washer actually seals off the lower passage to the ports?.....???
Thanks Peter!
- W


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## pyce (Nov 7, 2001)

*Re: Inside The Foot Valve (Ceilidh)*

Yes, yes and yes!







...... Basically the oil goes from top towards bottom. The main inner hole you see holds the rivet, sorry did not put it, no time today. The bottom thick washer is covering everything, so no oil goes through if there is no pressure. This whole thing sits at the bottom of the inner tube, just like the foot valve in the Koni Yellow....... I will give you a better picture some time tomorrow.


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## Ceilidh (Jan 7, 2004)

*Re: Inside The Foot Valve (pyce)*

Hi Peter,
Well, let's see: There's a washer-loaded non-return valve at the bottom, and up top an edge-mounted 2-stage washer/shim stack with a low-velocity bleed created by the thin annular washer at the very top (which creates a clearance between the washer stack and the bottom surface of the 4-pronged star clamp).
At lowest speed operation, the fluid passes between the uppermost washer #2 and the star clamp, then flows radially inwards and then downwards between the inner cylindrical boss and the inside edges of the washer stack. By varying the thickness of the purple annular washer #3, Boge can control the flow through the bleed.
With increasing cylinder pressure, the inside edge of washers #2 deflect downwards, admitting more fluid under the star clamp. Initially the stack is quite soft, as only the two washers above the yellow annulus #4 deflect. (stage 1)
With higher pressures and velocities, the top two washers come in contact with the remaining washers #5, and the valving effectively stiffens (2nd stage)
At highest velocities, flow is constrained by the annular gap between the washer stack and the cylindrical boss, and here the force curve adopts the classical velocity-squared profile. By varying the size of this gap (via washer inner-diameter selection), Sachs can control when this part of the curve kicks in.
.
Peter, have I missed anything really special? I'm not sure I see the "magic" in this mechanism. It's well-designed, with many operating parameters for the tuner to play with, but in the end it still looks like a shim stack (when I first saw how the washers were clamped down by the top coil spring, I thought for a moment there might be an inertial impact valve -- but the loadings and compliances go the wrong way....). Please tell me if I've missed something!!
- W


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## pyce (Nov 7, 2001)

*Re: Inside The Foot Valve (Ceilidh)*

Winston, I also think it works exactly in the way you describe it above! The whole “magic” actually does not exist, I misled myself and at first saw what I wanted to see, but it was not there







Then this quote:

_Quote, originally posted by *pyce* »_ .....The sad part is that yesterday I thought this is piece of art because I was thinking it works in certain way, but this morning discovered that it does not work that way! It actually works in a more conventional way......

So, try to look at the same section you were looking previously….. At glance I thought that the depth of the foot valve was kind of different and that all this was set to be a speed sensitive system, where the washers would deflect so much that by bending inward, they would get so close to the bottom surface that automatically would restrict the amount of oil going below the edge of the washers into the three holes! Basically I could not evaluate with naked eye how deep that round channel is (at the very bottom below the washers), so I thought that the washers do go close to the bottom of that channel under hard compression, therefore we had some sort of speed sensitive stack that at this point has great potential for being tweaked for “not bottoming” at extreme high speeds……. But once got the caliper and measured the depth, it was clear that it does not work that way. So, the "magic" was in my dreams







Sorry for the confusion...


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## pyce (Nov 7, 2001)

*Imaginary Foot Valve ....*

Here is a sketch that describes the "actual" vs. the "magic"...








1A - Actual Low Speed (Bleed)
1B - Actual High Speed (Determined by the distance between washer and inner wall)
2A - Imaginary at Low Speed (Bleed) - same as "1A"
2B - Imaginary at High Speed (Initial restriction controlled by the distance between washer and bottom portion of foot valve).


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## Ceilidh (Jan 7, 2004)

*Re: Imaginary Foot Valve .... (pyce)*

Peter, I am impressed with your ever-increasing sophistication! That was a clever possibility you raised, and in truth it never even occurred to me that that might be happening; hats off to you for considering it!








Now, if you're interested in this stuff (which is getting fairly subtle), let me just add a few things about this Sachs-Boge mechanism:
1) First of all, the very clever "imaginary" mechanism you described would be very difficult to tune properly (were it to exist in the shock):

_Quote, originally posted by *pyce* »_








2A - Imaginary at Low Speed (Bleed) - same as "1A"
2B - Imaginary at High Speed (Initial restriction controlled by the distance between washer and bottom portion of foot valve).

If there were a restriction between the washer and the bottom portion of the foot valve (as illustrated in figure 2B above), you would in fact get the high-velocity shut-off you hypothesized -- but it'd be very hard to control(!). What you would have in this situation is a positive feedback loop: if the valve begins to shut-off because of overly high fluid pressure in the cylinder, the resulting flow constriction will raise the pressure still further, which will deflect the valve even more, which will constrict the flow and raise the pressure still more, etc., etc. This sort of positive feedback can cause a lot of problems in a dynamic system:
In the extreme case, the feedback loop might slam the valve "shut" just when you most want some give in the suspension (i.e., as the car is landing on the ground after a jump) -- which would be very bad! But even if you properly sized things so that there's always reasonable clearance below the washer edges, you have a very real risk of "oscillatory" behaviour: in broad terms, you can easily run into situations where the valve begins to "flutter", so that a smooth increase in piston velocity will lead not to a smooth increase in damping force, but a wildly time-varying force that can lead to a lot of harshness.
It's partly for this reason that most of the valving systems you'll see have a great deal of intrinsic negative -- not positive -- feedback: pressure builds, the valve begins to open, the opening reduces the pressure, and the valve ceases to open further. This is the sort of feedback that gives you a nice progressive response to changing damper velocities. That's not to say that positive feedback can't be made to work -- but gosh it can be nightmarish for the control engineer in charge!
.
2) On a rather different note: the Sachs-Boge mechanism has some really nice features, now that (thanks to your great Solidworks models) I can see it in more detail. In particular, take a look at the round-bottomed, ring-shaped trough that lies under the washer stack:


_Quote, originally posted by *pyce* »_










Remember when we were looking at more simple valve designs, and I was mentioning how it's sometimes difficult to get the fluid moving where you want it to go (particularly just when the piston is starting to move, or has just changed direction or speed), and how you can get some ride harshness while you're waiting for the flowfield to organize itself? And remember how some subtle detail work right at the valve seat (washer edge) can do a lot to improve the response of the flowfield? (Detail work, by the way, that the Sachs-Boge rear shock has in spades.....) Well, this front shock mechanism goes one better:
If you look at how the trough sits below and outboard of the flowpath taken by fluid passing through the valve (Peter, maybe you could make a little cartoon to demonstrate for people, as not everybody has practice at visualizing fluid flow...), you'll see that the trough is basically designed to foster and contain a flow vortex -- that is, shock fluid passing through the valve and into the trough will set up a sort of rotating donut (with the flow rotating in a vertical/radial plane); the three outlet ports will siphon off some of the vortex, but otherwise there's a nice regular flow.
This is a good thing! Peter, consider what happens if the compression suddenly stops and the valve closes: with a normal valve mechanism, the flow simply stops everywhere, so when the compression starts again, the flow has to reorganize itself and start moving again; during this period of reorganization, we have poor control and harshness. But with the Sachs-Boge mechanism, when the valve closes, the donut-shaped vortex just keeps spinning along (by inertia); thus when the valve reopens, all the flow is already set up, and indeed the first fluid that enters the newly reopened valve is actually sucked into the vortex.
As a result, this mechanism should have excellent response to changing piston speeds and piston reversals -- that is, it should ride very nicely on the chatter bumps.
3) And finally, as I didn't make it too clear in the earlier post: from what you've shown us, the Sachs-Boge is a 4-stage shock: the initial bleed stage, the two washer-stack stages, and the final "orifice-flow" stage. Assuming that the shock tuner has some idea of what he wants (i.e., assuming he actually knows what to do with all these stages), this shock offers a lot of opportunity for subtle tuning.
So yes, I see your point: this is not a bad shock mechanism; not bad at all.....









- W

because no more fluid is entering the valve, not only does the primary shim stack shut off, but so does the flow-reversal valve


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## Brocken (Dec 29, 2004)

*Re: (pyce)*

cool, I might be waiting for the reds to come here.


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## pyce (Nov 7, 2001)

*Re: Imaginary Foot Valve .... (Ceilidh)*

Winston, thanks a lot for the detailed explanation! I am very glad that you like the design of the OE compression valves (both front and rear). I remember when we were starting all this, we all thought (or at least many of us) that the OE dampers are some poor quality stuff that VW got just put in there as to sell the car and that they were just good enough to take you out of the dealership, as they had to be cheap to produce, so VW would make more money, therefore Sachs did some cheap stuff to satisfy the cost request, etc..... Looking at the parts inside (and the concepts behind the design) the OE front and rear today, I think Sachs did great job not only in the design but in the development (tune) of the dampers and perhaps the only part where they could have done better (but that also means a lot more $$$) is the quality of the oil they used in those dampers. Were they to use some higher quality (and very expansive) oil - perhaps our dampers would have last for much longer without losing their initial performance....... Anyway, looks like that would be one of the next projects - drill, drain and refill existing used OE dampers with new and better oil and give them some longer term testing, dynoing, etc. that would be an interesting one and we will start soon a new thread on the matter, as I am sure many OE performance lovers would follow the results with interest. There are several things I would like to explore with the OE dampers (like re-valving and re-building the bodies, etc), but that is going to start only few weeks from now. Next step here is to model the rebound components, explore who it all works (it is very similar concept) and then perhaps build the rest around them (the tube, the body, the shaft, etc) so we have a real dimension virtually working model, which we can use to get some dimensions that would help us with calculating the flow through the foot valve per stroke, etc. At the same time I am extensively looking to get a mono-tube Bilstein and cut it, so we can see how that one is designed and explore the way it works. Phil has the equipment to revalve those as well, so ideally would be nice to explore some "GT" settings on a quick-acting mono-tube, which eventually would be the ideal damper to have - the "OE Ride Mono-Tube"









_Quote, originally posted by *Ceilidh* »_ ......If you look at how the trough sits below and outboard of the flowpath taken by fluid passing through the valve (Peter, maybe you could make a little cartoon to demonstrate for people, as not everybody has practice at visualizing fluid flow...), you'll see that the trough is basically designed to foster and contain a flow vortex -- that is, shock fluid passing through the valve and into the trough will set up a sort of rotating donut (with the flow rotating in a vertical/radial plane); the three outlet ports will siphon off some of the vortex, but otherwise there's a nice regular flow.......

Here is a sketch that shows (hopefully it is correct!) the "rotating donut" flow below the main stack of washers:


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## kevinstillwell (Feb 28, 2005)

*Re: Imaginary Foot Valve .... (pyce)*

I want to thank Peter for bringing this very interesting post to my attention. There are some interesting questions raised, and I like the fact that you go on to find the answers. 
My quest for supension related knowledge began in 1985, and is dirt bike orientated. It's interesting to see the piston designs used in cars, and the differences, and similarities to bikes. We started modifying dirt bike suspensions by removing the stock pistons and installing Works Performance 'orifice design' pistons. The direction this lead is a whole different topic, but orifice damping does fit with the Sachs rear piston design being discussed, since they are using the "flow control washer" to control the hole size.
Ceilidh has shown the ratio of fluid flow between mono-tube and twin-tube dampers. My question would be, how much are the shims deflecting? (deflection would be proportional to the fluid flow and piston design) If you had a rough idea of deflections, you could better tune the valving to meet your needs (as per the revaving that Peter and Phil have been doing) escecially since the shims non-linear characteristics have a big affect on the load-deflection curve. 
We might be able to make a rough guess at deflections if we knew the weight applied to each suspension unit, how much shaft travel do they use, and what is the piston diameter? 
Also, when the shocks were disassembled, how much air was in the unit? After relatively short use, motorcycle shocks get a lot of air in them. So much, they will often 'explode' upon disassembly, shooting oil accross the room. I'm curious as to the amount of air build up in car shocks. 
Kevin


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## Ceilidh (Jan 7, 2004)

*Re: Imaginary Foot Valve .... (pyce)*


_Quote, originally posted by *pyce* »_.....that would be one of the next projects - drill, drain and refill existing used OE dampers with new and better oil and give them some longer term testing, dynoing, etc. that would be an interesting one and we will start soon a new thread on the matter, as I am sure many OE performance lovers would follow the results with interest.......


Hello Peter,
You got the flowfield in the doughnut exactly right -- thanks very much! Once those vortices get set up, they're very difficult to shut off, and as a result the compression valve will start working the instant the piston starts to move; very nice design.








On a related note, however: I hope your future experiments also include the Koni Yellow/Red conversions you spoke of earlier -- much as I like the OEM mechanism, I'm actually one of those people who think the OEM shocks are a bit under-damped (even when new), at least for the type of roads and driving that I do.
If I had to guess, I'd hazard that the most difficult damping job (in terms of ride comfort) is handling the sort of concrete "freeway hop" and jolting that you have to endure out there in the Bay Area, and that the OEM dampers have been optimized to give the best possible ride on those surfaces. That's great for you and your neighbors! But for me, out here in Beantown, I'd actually prefer a bit more rebound control --- hence the Koni Yellow is still interesting to me, if only I could dial back the compression damping some. Hence it'd be great if you could compare your OEM experiments with what you can do with your modified Yellows.
Anyway, please keep 'em coming -- I can hardly wait to see what you and Phil (and now Kevin, evidently) have got cooking. All the best!
- W


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## pyce (Nov 7, 2001)

*Re: Imaginary Foot Valve .... (kevinstillwell)*

Folks, Kevin Stillwell is nothing less but the guy who has developed the “Shim Program” we were talking about on the earlier pages. More information about this fantastic product could be found on his website (www.shimprogram.com) Few weeks ago I sent him an e-mail with a link from this thread and here he is…..
Kevin, thank you very much for replying to my e-mails and for stopping by here. Sorry I did not have time to address your post earlier, but had been very busy the least few days. Lots of work lately and the free time I use to put all the parts from various dampers I have into 3D models, so everything could be assembled virtually, this to help us understand who exactly things work inside. It is a lot of work as some of the measurements are hard to get, but so far things are going pretty well. After all, we are not reverse-engineering the whole thing, but doing it more for education purposes. All I want to make sure is that we understand the way things work in the correct way, so we build a good base for the work ahead. It will be absolutely fantastic if you could point us to our mistake sin this thread, tell us where we went wrong as I am sure there are many things we did not get right. There is very little on dampers in the popular books ones could get around, and therefore we simply have to do it the simple way – “open and find out what’s inside and then think” approach. I am sure you could teach us so much, I just hope you will have the time and desire. There is a very long line of experiments coming in a week or two and it would be nice if you could tell us your thoughts on these. Basically, the goal is to apply a very “progressive” stack on the existing Koni Yellow Base Valve and see how that goes first. Before that, we are thinking to eliminate the pre-load completely as it really screws up the whole initial impact comfort issue, meanwhile not providing huge gains in the high speed where I would love to get gains to begin with. For what my feelings are of today, the pre-load is great stuff if you are after “quick-reacting” feel that helps some drivers to extract the best of their cars on a smooth track and perhaps helps a lot the initial phase in a curve, where you need to slow down the roll as early as possible, but for street use with poor quality roads I can feel more negative than positive about any pre-load. Correct me if I am wrong on this, please! …… So, eliminating the pre-load will perhaps give us some better control of the very initial part of the curve (the dyno curve I mean here) and later in the experiments we are thinking to eliminate the bleeds as well. Do not know exactly how is this going to affect everything, but Phil’s philosophy is that a damper should be in control as soon as possible when the movement begins, so a bleed is in a way a “bad” thing as it allows some free movement, at least in the initial part of the movement, before speed and pressure builds enough. His idea is to get a very soft initial washer as to almost compensate for the bleed, to a point that the comfort would not be affected noticeably, but the damper would act faster (earlier) and therefore have more time to build progression, which will eventually translate into better ride with ultimately more control. What are your thoughts on this? Basically, the main idea behind these experiments is to see if a super-progressive “dirt bike” type damper characteristics (which you and Phil are very familiar with) will work well enough on a street car that has to ride on bad roads more often than I wish. The goal is to make the car comfortable like OE (and better!) and at the same time make it almost impossible to bottom…… Anything you could share with us would be great! Thanks again for stopping by and for making that wonderful Shim Program!








peter


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## kevinstillwell (Feb 28, 2005)

*Re: Imaginary Foot Valve .... (pyce)*

Peter,
Thanks for the glowing review. 
From what I have read of your thread, you are not far off base. Using the 3D modeling to understand what is actually happening is a great way to get "inside" the suspension units. It would be very difficult to say if any of the theories on the precise working of the piston and valving are correct or incorrect. For that reason, I do always do two things:
1. Study a design and formulate a probable theory on what is going on inside the shock.
2. Conduct tests to try to prove or disprove that theory.
This basic approach lead to the development of the Shim Program. When I first started suspensions, it amazed me how little suspension tuners knew about shims. Most would (and still do) just guess and start swapping shims around to what patterns develop. 
You mentioned there are a series of tests coming in the weeks ahead to design a "very progressive" damping curve. This should prove to be quit interesting. 
Piston design and shim configurations have a great affect on preload, and my personal experience in our applications has shown that .0005" is noticeable. That is very difficult to get that kind of precision when assembling the shock. For that reason, we have abandoned the preload concept for the time being.

_Quote, originally posted by *pyce* »_
Correct me if I am wrong on this, please! …… So, eliminating the pre-load will perhaps give us some better control of the very initial part of the curve (the dyno curve I mean here) and later in the experiments we are thinking to eliminate the bleeds as well. 

I would say that eliminating the preload will give you a "different" means to control the low speed. From my experience, suspension tuning is just the "swapping" of symptoms. (e.g. You trade plushness for more bottoming control etc.) IMO, the different piston designs all strive for the same end result, which would be more tunability, and the ability to adjust different damping circuits independently of each other. This could lend way to tuning each symptom without affecting the other.

_Quote, originally posted by *pyce* »_ His idea is to get a very soft initial washer as to almost compensate for the bleed, to a point that the comfort would not be affected noticeably, but the damper would act faster (earlier) and therefore have more time to build progression, which will eventually translate into better ride with ultimately more control. 

This sounds like a good plan. If you are using a soft initial washer, then it sounds like you are going to a two stage shim stack design. Here is a simple diagram of a two stage shim stack. (The diagram is not to scale, and is for visualization purposes only.)








As you can see from the diagram, the trick will be to space the low speed shims the correct distance from the high speed shims. This would provide the initial movement equivalent of the bleed holes. Now we are back to the question, how much do the shims deflect (which is proprotional to the amount of fluid flowing through the piston ports). You'd need to make some sort of estimate to arrive at a starting point for the separator thickness. The next step would be to come up with a shim stack to achieve the desired results. It is most helpful to have the dyno at this point, because you can test the damper to see if you are getting what you want.
Now, if I misunderstood, and this is not the approach you were going to take, "never mind".

Regards,
Kevin
_Modified by kevinstillwell at 1:00 PM 3-2-2005_

_Modified by kevinstillwell at 1:04 PM 3-2-2005_

_Modified by kevinstillwell at 1:05 PM 3-2-2005_


_Modified by kevinstillwell at 1:06 PM 3-2-2005_


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## pyce (Nov 7, 2001)

*Re: Imaginary Foot Valve .... (kevinstillwell)*

Kevin…
Sorry for the very long delay. I am in a particularly busy period right now, so could not find the necessary time and concentration to respond to what you wrote….. There are so many things that I would like to ask you, do not even know where to start from. I so much wish we contacted you earlier, so you could go in real time with our small discoveries here and comment as we go. At this point now there are so many questions, that I feel like re-posting the whole thread one more time for you to read the specific areas where to me at least the puzzle is still too unclear. Let me try to start in here….

_Quote, originally posted by *kevinstillwell* »_Piston design and shim configurations have a great affect on preload, and my personal experience in our applications has shown that .0005" is noticeable. That is very difficult to get that kind of precision when assembling the shock. For that reason, we have abandoned the preload concept for the time being.

The question here is: Why do they (KONI for example, on the Yellow Sport dampers for our A4 VW) use pre-load? I do understand that the pre-load gives some great initial feel and it helps the curve to build strong much faster, but couldn’t that be achieved with no pre-load, using some carefully designed stack? Or maybe they are doing it on purpose, so it will not be easy this way for the aftermarket tuner to “tweak” the damper easily? Or is it just because those are Sport dampers, so a specific “curve” is necessary and that curve (dyno curve) could be achieved only if pre-load is used? Like for example – everything is concentrated in the very initial part of the stroke, for maximum fast response, meanwhile the high speed is pretty “weak” so to speak? Basically, if you look at the picture below, from what I understand, a smooth track damper needs some sort of curve that looks like the red one, where high speed is not really necessary, but initial response is a key factor. If that assumption is correct, then is the pre-load the only way to get close to that type of red curve, or perhaps if not the only way – is it just the easiest way and therefore they are using it? Or is it something entirely different?








I will come back later on to continue with the questions..... Have to run now. Thanks in advance!


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## kevinstillwell (Feb 28, 2005)

*Re: Imaginary Foot Valve .... (pyce)*

1. One of the questions was, "can the equivalent of a preloaded stack be achieved with no preload, using a carefully designed stack?"
You can manipulate the shims to take advantage of their non-linear characteristics, but there is a limit. That limit could account for the use of preload by the manufacturers. Preload allows that little bit of additional "stiffness" that can't be achieved other ways. The piston design also plays an important part in the overall scheme of things as well. 
First, shims have a couple basic characteristics. Here is a picture of a shim, and brief description of these characteristics. 








1. Shim loads are non-linear.
2. With thick shims, the loads start stiffer, and progressively get softer (compared to thin shims), and with thin shims, the loads start softer, and progressively get stiffer (compared to thick shims). 
There are handy formulas to convert shims from one thickness to another, but they don't take into account the non-linear characteristics of the shim. Below is an example. (def = deflection in inches, and the loads are in lbs/inch)








You can see the conversion is accurate at lower deflections, but the more the shims bend, the further the loads deviate. This demonstrates how the thin shims progressively get stiffer (compared to thick shims). 
In the above example, it shows a maximum deflection of .024 inch. This is assuming the shims in the shock in question to deflect .024. We would want to get an estimate of how much they deflect to for more accurate comparisons, but for now we can assume it to be .024.
So what does preload do? Preload adds more load to the beginning of the piston movement. Below is an example using the same 22.3 shim and adding .001 inch preload. 








The initial loads increased 50% by adding a meager .001 inch preload. The goal of preload is to increase the initial loads. So the question was, can this curve be achieved without preload?
If, for example, we started with a stack of thin shims, we could do this by converting the stack to a fewer number, but thicker shims. Below is an example of stiffening the initial loads of a 8 - 22 x .3 shims, by converting to fewer but stiffer shims.








In this case, we increased the loads initially, with lesser affect at the higher deflections, but it doesn't do it quit the same as preload. The preloaded stack increases the load initially, but the % increase tapers of faster than by converting the stack to thicker shims. (Compare the loads at .008 deflection. 21.8 vs. 29.0) 
Unfortunately, the Koni shock already uses .4mm thick shims. It's not really an option to increase loads by going to thicker shims. (Not sure if thicker shims are available. We generally use .1, .15, .2, .25, and .3mm thick shims) 
To achieve the red curve in the graph above, you would need a stiff initial damper that blew off at higher forces. 
First, a better understanding of the Force vs. Displacement graphs. Below, I've taken a graph from a motorcycle shock, and added the velocities. It's not in proportion to the car graphs, but it will show the relationship to the velocities and displacement. (Disclaimer, I don't have a dyno yet, and these are just observations I've made.)








Earlier in the post, it was mentioned that the Force vs. Displacement graph can give a disproportionate view. The velocities (inch/sec) are added to the graph in blue, and show that the majority of the velocities are reached very quickly. (Perhaps someone with more experience interpreting this type graph can shed more light.) 
Also consider, the dyno run only goes to 20 inches per sec. This is relatively slow, and the actual speeds on the vehicle could easily be double that. For perspective, jumping on the bumper could produce around 5 inch/sec. (rough estimate) 
Now back to the shims. It is the shim stack loads that control the movement of the piston. You can visualize how adding preload would square up the "knee" (9 o'clock) on the graph by stiffening the damping at the lower deflections.
Theoretically, I would like to see a stack that is Firm initially, Blows of Later (FiBoL) and then gets slightly stiffer again on high speed hits. It would look something like this.








In a rally car (or applications with long travel), the idea would be firm initial damping to hold the car up in the stroke, giving the vehicle a firm, controllable ride, but it could still blow off to absorb sharp impacts, and then stiffen again at the end in instances when the car goes airborn, and lands utilizing the full piston stroke.
So much for theories, back to reality. I will be interesting to see what you come up with to achieve your desired results.
Regards
Kevin

_Modified by kevinstillwell at 9:45 AM 3-10-2005_

_Modified by kevinstillwell at 9:50 AM 3-10-2005_


_Modified by kevinstillwell at 4:29 AM 3-26-2005_


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## 2beirish (Apr 28, 2004)

*Re: Thoughts from a Guru*

I've followed this thread for months, and found it interesting challenging my own prejudice for Bilstein dampers. I had an enlightening discussion about BMWs (just bought an 88 325iS with 34,000 miles!! in perfect shape I'm studying building up the suspension on) with Jim Rowe, Chief engineer and owner of Metric Mechanics this week. MM has been in the suspension and performance engine enhancing business for years, is a Guru in BMW tuning circles, and is a hugely respected contributor to Gateway Tech, the annual (though not this year) tech conference that the St. Louis chapter of BMWCCA generously puts on. Jim Rowe called and talked with me for more than an hour in response to an e-mail I'd sent asking for Info about building up a high performance engine. In discussion of suspension & damper performance, Rowe stated that he felt that Bilstein HDs and Sports (I'm extrapolating: we didn't get model specific) had TOO much preload, that initial hit created too much response from the heavily damped Bilsteins that overwhelmed springs unless they were quite stiff. Please note, this is MY interpretation of Rowe's statements: I have no technical expertise aside from what I've picked up in discussion forums, in study and from hands on experimentation with various cars: I don't want to misquote Jim in any way, and he was extremely generous in calling and talking to me for so long. He also stated that he has a great opinion of Boge Turbo sport shocks (stock on the 325iS for years): that the pre-load is softer, more comfortable and doesn't create a rebound effect with the springs. So does Boge make a set of dampers for MKIV chassis cars we could incorporate into this thread?


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## pyce (Nov 7, 2001)

*Inside the Rear Koni Red .....*

Hi Everybody!
Sorry for the long delay, but life had been very busy and unpredictable for the last two weeks, so there was no way for me to dedicate to this thread. As I said earlier, we had plans to get going with some interesting tests, and glad to say that the plan goes well so far, I just do not have time to post the results. It is not something that could be described with few words, so I better keep it off until my life gets easier and have time for detailed drawings, graphs, etc......
Kevin, I owe you detailed reply to your last great post, but it is not going to happen tonight, sorry! But just wanted to let you know that the info from your last post had been discussed a lot with Phil and we are even testing few of the things you suggested. Things are looking very interesting, even if not quiet as expected. There will be detailed feed back for you, but I really need time, so please be patient......
Anyway, the reason for this quick post out of the blue, is that tonight I finally found some time and took apart the Koni Red rears, so we finally now know what's inside and how did Koni get that different compression curve in the Reds vs. the Yellows......
I have no time for modeling right now, so here is the old model of the Yellow. Look at the left side, where is the "exploded" view of the washers over the foot valve:








Let's go bottom-towards-top. So, the Red Rears have the exact same foot valve. The next is the bleed-washer that in the Reds has the same diameter and thickness, but has two more cuts for total of four, that are positioned at 90 degree! The next washer is exactly the same. Now, the first small washer on top of the first two has the same diameter, but the thickness in the Reds changes from 0,4 to 0,25 mm, so it is thinner. All the rest above that is exactly the same (!) The other difference is that there is no pre-load on the stack. And that is it, folks! For the rest, the Reds are exactly the same as the Yellows......
There are several interesting things to talk about here, but perhaps will happen tomorrow. Good night!


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## Ceilidh (Jan 7, 2004)

*Re: Imaginary Foot Valve .... (kevinstillwell)*


_Quote, originally posted by *kevinstillwell* »_.......Theoretically, I would like to see a stack that is Firm initially, Blows of Later (FiBoL) and then gets slightly stiffer again on high speed hits. It would look something like this.








In a rally car (or applications with long travel), the idea would be firm initial damping to hold the car up in the stroke, giving the vehicle a firm, controllable ride, but it could still blow off to absorb sharp impacts, and then stiffen again at the end in instances when the car goes airborn, and lands utilizing the full piston stroke.
So much for theories, back to reality. I will be interesting to see what you come up with to achieve your desired results.
Regards
Kevin


Hello Peter,
I just wanted to mention that this brilliant post by Kevin Stillwell (Kevin, thanks very much for your contributions -- this has been wonderful!) includes a very succinct description of the sort of damping curve we were debating a few weeks back. To reiterate:
1) One can understand and appreciate the benefits to the smooth damping curves you're working on with Phil, but there's still some question regarding the overall shape of the curve. Whilst strong "jump/landing" compression damping seems to be desirable at the highest piston velocities, and relatively soft low-velocity damping can help roadholding and general ride serenity, it's not yet clear whether the high and low parts of the curve should be joined by a simple line.
2) In particular, a potential difference between car vs. motorcycle damping lies in the need (in a car) to control roll. If the damping rate in an automotive shock is too weakin the lowish velocity range, a car can start to feel sloppy upon corner entry or in left-right transitions; it's to prevent such sloppiness that the Bilstein curve is so initially steep (though from what you report, Bilstein has perhaps overdone it somewhat!). In contrast, a motorcycle can have shocks tuned more specifically for roadholding or ride comfort in that lowish-velocity range, as there is no "roll" that has to be controlled; hence the damping in that range can be relatively weak.
3) The caveat to the above is (as you pointed out a few weeks ago) that whilst motorcycles don't have to deal with roll, they do have to contend with pitch, and the shock velocities in motorcycle pitch are probably not hugely different from the velocities in automotive roll. In fact, it's this aspect of damping that has me really intrigued by what you and Phil are doing: if Phil's "smooth" damping curves can adequately control motorcycle pitching (in effect, by strongly snubbing the fast initial part of the pitching motion, and then relaxing the damping as the pitching motion slows down....), then perhaps we've been overdoing it in cars. (In other words, can't wait to hear how your experiments progress!)
4) That being said, however, there's a caveat to the caveat







: with cars, unless you go to active or semi-active roll control, the total amount of roll is dependent upon such "passive" parameters as vehicle speed, CG height, roll center geometry, and sprung roll rate; in contrast, with motorcycles you can cancel out all of the pitch under acceleration (via the geometry of the rear swing arm and the routing of the drive chain (if any), as well as part of it under braking (at least that part of it associated with the rear brake). Hence if you see a motorcycle resisting pitching even under wild acceleration, you might be seeing the effect of clever geometry, not of shock tuning. (Braking, however, is different -- if Phil can control brake dive with his smooth shock curves, I'm all ears!)
5) Anyway, there's a lot to be said for Kevin's damping profile: somewhat steep at lowish piston velocities for roll control; shallower at highish velocities to "blow off" the effect of sharp bumps; and then steepened up again at the rarely-encountered highest velocities, for smooth snubbing of post-bump landings.
6) To the above curve I'd add my own request: For me, I would think that just before the "Firm initially" there should be a small regime where there is almost zero initial resistance, and then a smooth concave-up (in Force-Velocity plot) ramp to the "Firm initially" section; this concave-up nose would hopefully kill some of the initial hit and small vibrations (allowing us to use smaller rubber bushings, which cause some control problems of their own in certain situations), and would ideally allow the car to "float" a little better over subtle road undulations. Making this nose too wide would of course lead to float and wallow, so it should be quite brief, but a little bit might be nice.
I guess the bottom line is that there are a number of shock profiles to potentially test out, and the results of your upcoming experiments will be quite useful in validating one philosophy or another. So please keep 'em coming!








- C


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## pyce (Nov 7, 2001)

*How much do the washers flex?*

Just got back from the shop. Decided to invest today's time in experimenting precisely the above mentioned FiBoL (Firm Initially, Blows of Later and then gets Firm again in the high speed) so to be able to put them in the car later and see how that works.......
So, the plan was to use a valving that we have dyno graphs of and I have seat time on that same valving. Decided to go with the Rear Yellow V1.3, which has basically the compression curve of the Rear Red, even if achieved in a different way (as now we know the Reds get that curve with 4 bleeds and we have 2 bleeds only in the Yellow, but softer washers do compensate some and both dampers feel pretty darn the same on the road, plus having almost identical dyno curve). Here is where we started from:
V1.3
Bleed Washer
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.1
14 x 5.5 x 0.1
8 x 5.5 x 0.6
Screw Head
Sorry, no 3D models for now, I am very busy with other stuff, but they will eventually come. For now use your imagination or draw it at home on piece of paper following the posted dimensions.
To achieve the FiBoL graph that Kevin posted in his last post, decided to simply introduce a "spacer" washer on top of the last 14 mm washer, and that "spacer" would be 8 mm outer diameter, so we maintain the initial curve exactly how it was before (this way to see more precisely where and how this second stage kicks in)....... Here would like to remind you all that when we opened the Rear Yellows for first time, we saw those "spacer-washers" for the stage two and three and they were thickness 0,4 mm and 0,7 mm. If you all remember, I mentioned that Phil saw that and made a comment that in ordinary driving, in our daily life, those "spacers"were way too thick and therefore the second and third stages would never kick-in, unless you air-born the car and smash it down, but by then perhaps we would have many other things to worry more about that simply bottoming out. Based on his observation then, I decide to go with much thinner spacer, so the new valving looks like this (in bold the spacer and the "stage two" washer):
V3.0
Bleed Washer
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.1
14 x 5.5 x 0.1
*8 x 5.5 x 0.2*
*16 x 5.5 x 0.35*
8 x 5.5 x 0.6
Screw Head
Called this V3.0 as the "3 series" will be dedicated to FiBoL and in case you are wondering what the "2-nd series" was - it is some experiments with spacers between the foot valve and the washers that not only eliminate preload, but do restrict high speed flow, but more on those in a later stage as it is still work in progress...
Well, the idea in the above valving was that at some point in the mid-speed those 14mm washers would flex more than 0,2 mm and would hit the thick 16 mm. washer on top of the spacer (the "Stage 2") and as that is one thick washer (0.35 mm) the flex would slow down dramatically, therefore we would have some "spike" at the high speed and therefore we would achieve the FiBoL dyno graph that Kevin posted.......
Guess what? ....... Even at the highest speed we tested (30,00 in/sec) the dyno curve did not change at all (!) Now, someone correct me if I am wrong, but I would conclude that those "soft" 14 mm washers in reality can not bend more that 0,2 mm, therefore the whole "2-nd stage" could not even start working at the speeds we tested. If that is correct, the much "thicker"original Koni "staging" would really never work, not a chance! 
Tomorrow will try to find 0,1 mm spacer, so will get the V3.1 and see if that is enough to at least touch the thick washer in the second stage...... At least we now know little bit more about who much those washer do (or actually "do not") flex.


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## kevinstillwell (Feb 28, 2005)

*Re: Inside the Rear Koni Red ..... (pyce)*

Peter,
To clarify your post with the Rear Koni Yellow Compression Valve diagram, could you show a couple Force-Displacement dyno graphs for the rear Koni yellow vs. rear Koni red? Two different graphs of different velocities would be nice. Then we can compare the internal differences to the forces.
Also, can you list both shim stacks for comparison, including the diameter & thickness of the bleed washers. 
Just food for thought. It was mentioned that the first separator shim is thick enough that it prevents the face shims from making contact with the shim directly above it. We know this to be true at slower velocities. We're not sure exactly what is happening at higher velocities. 
However, after looking at Peter's super cool 3D renderings, I have to wonder how the cupping action of the face shims affects the oil flow as it escapes from between the two shims in questions.


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## kevinstillwell (Feb 28, 2005)

*Re: How much do the washers flex? (pyce)*

Two things are being guessed at, and need to be nailed down (or at least come up with a close approximation).
1. Velocities - What are the actual velocities of the damper on the car for various type bumps.
2. Deflections - How much are the shims actually deflecting? It sounds like Peter's next test will help determine this.


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## kevinstillwell (Feb 28, 2005)

*Re: Imaginary Foot Valve .... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_

a potential difference between car vs. motorcycle damping lies in the need (in a car) to control roll. If the damping rate in an automotive shock is too weak in the lowish velocity range, a car can start to feel sloppy upon corner entry or in left-right transitions; it's to prevent such sloppiness that the Bilstein curve is so initially steep.
motorcycles don't have to deal with roll, they do have to contend with pitch, and the shock velocities in motorcycle pitch are probably not hugely different from the velocities in automotive roll. In fact, it's this aspect of damping that has me really intrigued by what you and Phil are doing: if Phil's "smooth" damping curves can adequately control motorcycle pitching (in effect, by strongly snubbing the fast initial part of the pitching motion, and then relaxing the damping as the pitching motion slows down....), then perhaps we've been overdoing it in cars. 


I like the comparison between car "roll" and motorcycle "pitching". But this leads to a question for my 'non-car orientated' mind. 
First, car roll is self-explanatory, and is depicted in a nice diagram on page 4 of this thread. I think of pitching (for bikes) as the initial resistance needed to keep a motorcycle level as it navigates the course (or roadway). e.g. To soft on the front, and the nose would dive to easily as you chop the throttle to enter a rounded corner. Motorycles use a couple means to control this. One being spring preload. Forks, for example, may have 10mm preload on the spring. This helps hold the front up, and provide an initial firm feel.
Now my question. Do cars utilize any form of spring preload? Also, what are the wheel travel vs. shaft travels for car dampers. A brief explaination of the front and rear design would help me gain a better understanding of exactly what's going on.

_Quote, originally posted by *Ceilidh* »_
with motorcycles you can cancel out all of the pitch under acceleration (via the geometry of the rear swing arm and the routing of the drive chain (if any), as well as part of it under braking (at least that part of it associated with the rear brake). Hence if you see a motorcycle resisting pitching even under wild acceleration, you might be seeing the effect of clever geometry, not of shock tuning.


Again, the bikes have characteristics not shared with cars. The rear of a bike will want to "rise" under acceleration, due to the torque effect of the chain. (Put the front wheel of a bike against a wall, sit and compress the rear, and slightly engage the clutch. You will feel the rear rise up). So you have counter acting forces; the weight bias has shifted back under acceleration, causing the rear to squat, and the chain torque causes the rear to become more rigid and want to rise up. I want to minimize my compairsons to motorcycle, as we are dealing with car dampers, but thought this might be worth mentioning. 

_Modified by kevinstillwell at 7:58 AM 3-27-2005_


_Modified by kevinstillwell at 8:00 AM 3-27-2005_


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## Ceilidh (Jan 7, 2004)

*In Praise of Koni Reds*

Hi Everyone,
I'll post up a full report once I finish the initial set of experiments, but here's a quick heads up (mostly because I promised Peter I'd say something right away







):
I've just installed Peter's Koni Red shocks on the rear of my 1.8T GTI (which formerly had Koni Yellows front & rear). Peter has previously stated that this is *THE* shock to employ for spirited real-world driving on bad roads (at least among the commercially-available offerings; he and Phil are also working on some custom tunings....). With the caveat that I've not tried the various Bilsteins etc. that Peter has gone through and generally found less comfortable than the Koni Yellows, at this point I'd have to concur:
With Koni Reds replacing the Yellows at the rear of my GTI, my ride comfort has gone up considerably (to almost stock-levels of comfort at the rear); and handling is quite good (better than with comfort-tuned Yellows front & rear). This is by far the best handling/comfort balance I have yet experienced on my car.
Full report forthcoming, after I play a bit with rebound settings....
- Ceilidh


_Modified by Ceilidh at 6:20 PM 3-29-2005_


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## nogo007 (Jul 17, 2004)

*Re: In Praise of Koni Reds (Ceilidh)*

Hi Winston - What setting are you using for the rebound? Are you pairing them with stock GTi springs or aftermarket?
I have the Reds (on full soft) on my Mk3 paired with HR OE Sport springs and I find that the ride is just a bit floaty at highway speeds and large bumps. 
Overall, I find the ride to be still a little jittery on uneven surfaces but is much better compared to the Neuspeed Sport + Bilstein Sport combo that I was used to.
Nice dampers otherwise and much cheaper than the yellows.
-Omar

_Quote, originally posted by *Ceilidh* »_Hi Everyone,
I'll post up a full report once I finish the initial set of experiments, but here's a quick heads up (mostly because I promised Peter I'd say something right away







):
I've just installed Peter's Koni Red shocks on the rear of my 1.8T GTI (which formerly had Koni Yellows front & rear). Peter has previously stated that this is *THE* shock to employ for spirited real-world driving on bad roads (at least among the commercially-available offerings; he and Phil are also working on some custom tunings....). With the caveat that I've not tried the various Bilsteins etc. that Peter has gone through and generally found less comfortable than the Koni Yellows, at this point I'd have to concur:
With Koni Reds replacing the Yellows at the rear of my GTI, my ride comfort has gone up considerably (to almost stock-levels of comfort at the rear); and handling is quite good (better than with comfort-tuned Yellows front & rear). This is by far the best handling/comfort balance I have yet experienced on my car.
Full report forthcoming, after I play a bit with rebound settings....
- Ceilidh

_Modified by Ceilidh at 6:20 PM 3-29-2005_


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## banjomike (Feb 1, 2005)

Finally I caught up with this thread!!!
At some point along the way I went to the Bilstein website and I looked up the part numbers for the dampers that they make for the mkIV platform. I noticed that the same part number applied to the Golf, Jetta, and NB. I got curious so I did a search for those part numbers to see ho many different cars they sell that particular damper for. I only came up with one other hit. The Audi TT. Which got me thinking. What dampers does Audi put on the TT from the factory? Does the TT have a standard and a sport suspension? I wonder if the stock shocks from a TT might not provide a decent ride and last longer than the standard fittings on a lowly Golf? Of course this also got me thinking about springs, but that is a different thread


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## Ceilidh (Jan 7, 2004)

*Brief Koni Red Report*

Hello Folks,
I was hoping to post a full report on the Koni Reds (on the rear of my 2000 GTI, with Koni Yellows in front), but unfortunately there just isn't time. Perhaps later I'll add more, but for now let's just say that:
1) With Reds in the back (and Yellow in front), the car is more comfortable than with Yellows all around.
2) In its most comfortable state (1/4 turn rear, 3/16 turn front), the Red/Yellow combo is slightly better handling than the most comfortable Full Yellow setup (same settings).
3) Not surprisingly, given Peter's favorable impressions of the Koni Red when used on his San Francisco freeways, the Red/Yellow combo is most impressive on urban Interstate highways (e.g., I-287 in White Plains, NY), where sharp expansion joints and seams are encountered at high speeds. On these roads, the Reds largely eliminate the jolt & upset experienced on Yellows.
4) The combo is somewhat less impressive on New England frost heaves (the roads here, even when unbroken, are not flat: there are invisible waves caused by the annual soak/freeze/thaw cycles). Here, the mismatched compression damping between the firm Yellow fronts and the softer Red rears makes it impossible to eliminate a subtle pitching motion that continuously jostles the car. It is because of this pitching that I am using a rear setting firmer than Peter's (Peter had his Reds set at full-soft); dialing up the rear rebound to 1/4 turn (actually, about 10 degrees beyond 1/4 turn) reduces the pitching somewhat, at the expense of increasing the jolting on sharp bumps. If I had to guess, I'd conjecture that Reds all-around would permit a softer rear setting, making the ride even more comfortable. As it is, the ride is much better than with Yellows all-round, but it's still not serene: the car "walks" around incessantly, and on some surfaces can still feel a little jittery.
5) At least subjectively, the Reds feel like they have more rebound than do the Yellows (when placed at comparable settings). With the Red rears at 1/4 turn, my car has less initial understeer and less transient roll than it did with 1/4 turn Yellows.
6) Bottom line: if Koni carries through with its rumored intention to import the Golf/Jetta IV Reds to North America, then they might be the way to go for a mild street vehicle (i.e., excellent near-OEM quality ride comfort with improved handling and longevity). This conjecture is based on experience with the Red rears only, as we did not have a front set to try out.
.
Sorry for such a (by Ceilidh-standards







brief report, but I wanted to move on to the next topic.....


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## Ceilidh (Jan 7, 2004)

*Some damping curve musings*

Hello Again (this message is primarily for Peter, and is overly technical....but if you like technical, go for it!







),
On the drive up to Beantown, I had time to think a little more systematically about damping. Basically, I think Peter & Phil might be on to something with their "linear" damping curves, at least in the velocity ranges thus far covered in this thread. Here's the reasoning:
1) Passenger car suspensions are basically designed to take the energy caused by random bumps, and transform that energy into a 1-to-1.5 hertz vertical bounce. (In techie terms, the suspension acts as a bandpass filter centered at a resonant frequency in the 1 to 1.5 hertz range....)
2) The roughly 1-to-1.5-bounces-per-second resonance is chosen because vertical bounces at that frequency are perceived to be quite comfortable. (In simplistic terms, human beings have evolved so that we don't get nauseous or feel uncomfortable every time we walk: when we walk, we bounce vertically up & down at roughly 1.5 hertz -- and yet we barely notice it....) If we can keep suspension motions in this regime, we'll be in good shape, comfort-wise.
3) Thus when a well-designed car encounters a bump, it ideally cycles up and down at ~1-1.5 hertz, with the velocity varying as a sinusoid (this is merely the property of a simple harmonic oscillator, which is remarkably well mimicked by the human bouncing-motion-when-walking). At the top and bottom of each bounce, vertical velocity equals zero; as the car body crosses equilibrium, the velocity is at a maximum.
4) The above-mentioned 1-1.5 hertz vertical bounce is what we want to damp out when we drive our cars on bumpy roads: in simplistic terms, when we hit random bumps, those bumps are transmorgified into a 1-1.5 hertz heaving motion that we castigate as "sway", "float", and "imprecision". If we damp out those motions, the car body remains relatively steady while the wheels dance crazily underneath, which maximizes handling, roadholding, and driver comfort.
5) However, we can't just apply the damping willy-nilly. If we want the vertical bounce to be comfortable, the damping must be linear over the velocity range associated with the bouncing (that is, the damping force has to vary in direct proportion to velocity; on a force-velocity curve, the trace would be a straight, sloping line). Linear damping allows the bouncing motion to remain sinusoidal. Any other damping curve causes the bouncing motion to deviate from sinusoidal, which we as human beings perceive as uncomfortable (it'd be as if, while we're walking, the ground randomly heaved up or down, thus randomly changing our vertical velocity-from-walking). So to keep things comfortable, the damping has to be zero at zero velocity (i.e., no friction or "stiction"), and then ramp up linearly to the maximum velocity experienced at full bounce.
6) (Unfortunately, a car's suspension produces more than just pure bounce: there's invariably some pitch and roll as well, both of which occur at higher frequences (and thus involve higher shock-absorber velocities) that I don't have time to calculate.







But let's ignore these for now....)
7) Ignoring rally-style jump-landings for a moment, when we get to shock piston velocities far above the "bouncing" regime, there's little reason to make the damping forces high. Above this regime, we're not trying to control the relatively slow motions of the car body, but rather that of the unsprung mass as the wheels chatter up and down over bumps. For the most part, we don't want to damp this chattering: if the wheels are free to chatter up & down, the chattering motion doesn't work its way into the body motion; if the dampers are stiff at these speeds, however, they'll transmit bangs and jolts into the chassis of the car, which will make the ride uncomfortable (in effect, the damping serves to ruin the "bandpass filtering" effect of the overall suspension design). So we have a desire to roll off the damping at piston speeds higher than those pertaining to chassis bouncing (i.e., 1-1.5 hertz).
8) One caveat to the above is that if we make the high-speed damping too floppy, we lose control of the unsprung mass and the wheels begin to bounce off the road -- which is bad for tire longevity as well as handling and ride. But in practice, if we have low unsprung mass (as we do with our VWs), the damping we use to control the sprung mass will suffice to control the unsprung mass, so we don't really worry too much about this possibility.

.
9) Ok, how about some numbers? What velocities should define the linear regime?
..a) Let's assume a 4" bounce amplitude (peak to trough) and a bounce frequency of 1.2 hertz. Peak velocity in a harmonic oscillator is omega*A, where A=2" and omega=2*pi*1.2hz, yielding a velocity of ~15 inches/second.
..b) How about a rally-style jump landing?







Hmm. That's a little harder: usually when we "yump" a car, the tires don't actually leave the ground*, and the car "lands" on the back side of the bump, which effectively "cushions" the landing. But let's use an extreme case: let's say we drive the car at high speed straight off a high curb (say, 6"), and land on the flat pavement beyond. With these assumptions, we can calculate the vertical velocity of the car when it lands (which will be the max velocity experienced by the shock pistons). This velocity is given by the kinematic equation for the velocity of a dropped object at constant acceleration:

V^2 = 2 * (acceleration due to gravity) * (distance dropped)
= 2 * (32 ft/sec/sec) * ( 6")
V = 68 inches/second
(* -- we're talking about street vehicles here, not off-road or competition cars. A real rally car will definitely jump with its wheels clear of the ground, and sometimes it'll land very hard on the "wrong" side of a bump. In those cases the velocities will be much higher....)
.
11) Ok, Peter, there you have it: according to this (admittedly simplistic) analysis, if you want to go for maximum ride comfort, you'll want a linear damping curve up to at least 15 in/sec, and possibly up to 4X that figure, if you want a smooth cushion on rally-style jumps (unless you take Kevin's suggestion of rolling off the damping in the region between 1-1.5 hz bouncing and rally-car landings)..
If the above even remotely holds true, then some of the aftermarket shocks you've tested are rolled off at too low a piston velocity: the damping is thus reduced at speeds still pertaining to body motions, and the uncomfortable "kink" is squarely placed amidst the velocities produced by normal road bumps. So if you're trying linear "Phil-style" damping curves, you have some theoretical justification: by taking out the kink in the 0-15 in/sec region, you should be improving comfort, and by leaving the damping highish at the 15 in/sec region, you'll still be controlling float, heave, pitch, and possibly roll.
Interesting, interesting..... looking forward to hearing more of your results!
- W



_Modified by Ceilidh at 5:03 PM 4-4-2005_


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## Ceilidh (Jan 7, 2004)

*Damper musings (continued)*

Ok, here's a rough illustration.








Below, I've copied one of Peter's old plots (from the first page of this thread); it's a Force vs Displacement graph of the OEM rear shock, with different-coloured lines corresponding to different maximum speeds. In this sort of plot, a linear damping curve produces a smooth ellipse; if the ellipse becomes flattened at the top or bottom, the flattening is indicating a non-linear roll off of the damping at high piston velocities. If the roll off is severe and features the previously-mentioned "kink" (i.e., a kink in the Force vs. Velocity curve), the curves here would be so flattened that they start to look more like rectangles than ellipses.
On the plot below, the line to look for is the fuschia-coloured 8.00 inch/sec curve (between the dark blue and the brown traces). This curve shows the damping force exerted by the shock on a 2" (peak to trough) oscillation, which is well within the normal range of body motion while driving on a pretty-good-but-not-perfect road (i.e., we'd expect the body to move around this much on a normal, indifferent Interstate). Take a look at the shape of this line both in compression (top part of the plot) and in rebound (bottom part):








Notice how smoothly elliptical the compression (upper) curve is, and how the rebound (lower) curve is almost a perfect ellipse as well? These curves show that the OEM shock is linear in this regime, and they're consistent with how the OEM shock feels on a smooth highway: nice and smooth!
(Before we move on, look also at the rebound curves for velocities higher than 8.00 in/sec: see how flattened they are, and how the peak damping forces essentially remain the same? These curves show that the OEM shock is strongly rolled off at velocities higher than 8.00 in/sec, and are consistent with the general observation that the stock car doesn't ride that well at high speeds: when the chassis starts moving around under the influence of high speed bumps (e.g., at a 3" trough-to-peak bounce, the piston velocities are about 12.00 in sec), the damping to too weak to control the motion, and the roll off at 8.00 in/sec wrecks the sinusoidal ride we should be aiming for. If the current theory holds, the result should be poor handling PLUS poor ride comfort at high speeds....)
Now, in contrast, take a look at the same sort of plot for what Peter has found to be a very uncomfortable shock, the Bilstein TC Sport. Once again, look for the fuschia 8.00 in/sec line:








Here, the compression line is unfortunately hard to interpret because of the compressed scale, but the squaring of the rebound line is easy to discern (the compression line is actually squared in the same fashion, but the squaring takes place at such a low velocity that it's hard to see). This is a highly non-linear, strongly kinked curve, meaning that in a normal 2" oscillation on the highway, the shock is not allowing the car body to bounce in a smooth sinusoidal fashion. The result should be a ride that feels "jittery" on a smooth road, and downright harsh when the road gets rough.
The final plot to look at is the Koni Yellow (at full soft), which according to Peter is much more comfortable than the TC, though not as comfortable as the Koni Red or OEM. Here, the colours have unfortunately changed, and you should be looking not at the fuschia line, but instead at the brown 8.00 in/sec line just outside the fuschia trace:








Here, we see a curve that's essentially in between the smoothly-elliptical OEM and the severely-squared TC -- which is consistent with the Koni Yellow ride comfort winding up between those two other shocks. But notice here how high the compression curve becomes (it's essentially double the others), and how soft is the rebound (its peak is actually softer than the OEM); there characteristics reduce both the Yellow ride comfort, and the handling at full soft.
.
Anyway, as far as I understand it, what Phil and Peter are trying out is something that looks like the OEM curve (linear / smooth ellipse at body-bouncing speeds), but which perhaps is a little stronger, and which maintains the linearity at fairly high piston speeds. The hope is that by doing so, they can use the high-velocity damping to maintain good control of the sprung mass (and the above calculations show that the sprung mass can reach pretty high velocities on rough roads and during maneuvers), while still retaining good ride comfort through the use of a linear curve (which preserves the sinusoidal ride motion). (Peter, I still think you might perhaps gain something by rolling off the damping at speeds above 15-30 in/sec, but that's a matter for experimentation....)
So that's the theory; now we wait for the results of the experiments.








Cheers, everybody
- Ceilidh

_Modified by Ceilidh at 7:36 PM 4-4-2005_


_Modified by Ceilidh at 7:44 PM 4-4-2005_


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## pyce (Nov 7, 2001)

*Bilstein HD vs. Sport - Finally!*

Sorry everyone for the long delay. Our experiments are going at very good speed, I just have absolutely no time to report here on the results. And it is going to be like this for quiet some time. I will try to find a window tonight and write few things, as it is really getting interesting, but there will be no graphs, no maps, nothing like that for the moment. I will just try to describe everything with words and later in the month some graphs and renderings will follow.......
But this one just in, and you all have been waiting for it for very long time!
*Bilstein HD vs. Bilstein Sport*
Just got the results from the dyno and have to say that the valving (or whatever else that affects the numbers that the damper makes) may not really be the same! We compared a rear HD with about 1.000 miles on it against a rear Sport with more than 100.000 miles on it and the Sport showed still considerably stronger at all speeds! And it is stronger on both compression and rebound. We are talking about 30 lb difference on some speeds...... Now, from the graphs it looks like the shape of the curves is similar, so they both would offer similar driving "feel" (character), but at the end the Sport will be less comfortable, as the difference is well visible even at very low speeds and most of all, as soon as the damper moves. Of course, the graph would show more than the words, but as I said, no graphs for now, as I simply have no time to elaborate them. 
However, for the real final answer on this, I have to find relatively new Sport and dyno it again, as we have to see how much those curves got "weaker" for the 100.000 miles, as to determine better by how much the valving makes those two dampers different. I will also open the Sport and do a complete modeling later in the month, so we can explore it better and understand more in depth how it works and what opportunities it offers for revalving.
Kevin and Winston - Please be patient with me, things are going in the right direction, I just can not find few hours free time to describe everything. In few words, I spent a lot of time last week doing tests on the "Restrictor Washer", which is something the Koni did not have. It was an attempt to quantify and understand what would restricting the high speed flow give us, and the results are very interesting, I just have to describe them later. The later part of the week I spent in trying to get that "Linear" stack (the one Phil is so good at and Winston described in his last post). The whole problem was that Phil was not in the shop most of the time (he spent lots of time on some tracks doing tests) so I had to just do what I could and if Phil was there, he could have saved me tons of time by telling me what would work and what would not, so I did not have to "waste" time to test things that did not do a squat







But as he always says: "There is no wasted test, you can learn even more from the bad results!", so at least I can now tell you what does not work. As for the "Staged" stack - I could not find thinner washer for the separator, so we had to order one and once it arrives, we will resume those tests....... The good news is that the "Linear" stack works really well on the car! There is some tweaking to be done as to smooth-en even more the very initial opening of the washers, but I love the results at the high speed - the car really stays "high" when going over bumps and the bottoming is gone (at least in the ordinary street driving). The results are so good, I am willing to even try higher levels of high speed, and at the same time making the initial opening even easier and smoother, so the line (force vs. velocity) gets absolutely straight and pretty steep....... I do understand that this is very contrary to all our talks here and it is not easy to explain why exactly this linear stack works so well in controlling roll, but it actually does control roll, at least that is the feeling. It feels like there is anti-rolling device on the rear that limits ultimate lean. The nice part is that squat is reduced some as well, which makes me think that we need to look again in more depth into how dampers exactly affect body and spring control and most of all, revise the speeds we think the damper works in different situations. Bottom line is this - having a very soft initial curve, with very low values (the softest we have seen since day one!) and ramping it up in a linear way to pretty high values for the high speed, does actually reduce roll, but it does it in a very gentle way, without sacrificing ride quality. Now, try to imagine how a "progressive spring" would work - would be very nice in straight line driving, very soft and gentle, offering great comfort, but as soon as you lean on it, it will stiffen and would gradually decrease roll the more you are leaning on it....... well, I am experiencing something very similar with the "linear" stack. But more on that later, I have to go now.


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## Ceilidh (Jan 7, 2004)

*Re: Bilstein HD vs. Sport - Finally! (pyce)*

Hi Peter,
Just a quick comment on your last post (alas, I've run out of time as well!): I did some back of the envelope calculations last night, but haven't had time to refine & post them, but in fact it does look like body roll can involve higher piston velocities than we've been assuming -- so it makes sense that your linear curves do a reasonable job controlling roll. It'll take me a while to do the calculations right, but at the moment everything you're doing looks consistent with theory. There are a few other things I've been thinking about too, but they'll have to wait for a future week. Take care, and thanks for all the experiments!
- W


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## nogo007 (Jul 17, 2004)

*Re: Bilstein HD vs. Sport - Finally! (pyce)*

I have 2 rear Sports lying in my garage from a Mk3 with ~ 60,000 km's on them - if you need those to tear apart or for tests, let me know.
-Omar

_Quote, originally posted by *pyce* »_
...
However, for the real final answer on this, I have to find relatively new Sport and dyno it again, as we have to see how much those curves got "weaker" for the 100.000 miles, as to determine better by how much the valving makes those two dampers different.
...


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## pyce (Nov 7, 2001)

*Bilstein HD vs. Sport - More info ....*

After spending some time exploring the HD vs. Sport dyno plots, it is even more obvious that these two dampers are valved differently! The big difference is in the low speeds (from 2 in/sec to about 10 in/sec) where we have:
1. Much more pronounced "knee" in the Sport.
2. Much higher value of the force after the knee in the Sport.
Just to give some idea of the difference in values here - For example, the curve that the Sport provides at 2 in/sec is almost identical to the curve that the HD provides, BUT at double the speed (4 in/sec)! And the same goes with all the speeds until 10 in/sec where the difference gets little bit less..... and as a reminder, we are talking about a damper that has 100.000 miles versus almost new one! 
There is really no way in the world these two dampers have the same valving! Or, if indeed the actual washers are exactly the same inside, then there is design changes in either the piston or somewhere else, that affect the way the washers perform. I do not know yet who exactly these are assembled inside, but from the way the curve look and from the way it acts (big difference in low speed, less difference in high speed) may as well be just different preload on the washer stack (if that is possible in these dampers). In fact, the curves of the Sport vs. HD look very similar to the comparo we had time ago when trying different pre-loads on the Konis...... I will try to get some graphs soon, but till then just have to take the words here. I would do my best to locate a brand new Sport and dyno again, so we compare apples to apples.
Omar, I will send you an IM later, so we talk in details, but I am more interested in A4 Bilstein Sport with low miles, so we can see by how much different they are.....
Winston, I am discussing your theories about the linear dampers and your calculations with Phil as we speak. I will tell you more later on his take, but my guess is that you are absolutely right on the money, as in reality this damper performs very well on my car, plus it had been Phil's way of preventing bottoming in the bikes for years. More later, but thank you very much for your (as always) very detailed explanations and for the write-up on the Reds! Hope all this work you have done will help many here to make the right choice for their application.


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## kevinstillwell (Feb 28, 2005)

*Re: Bilstein HD vs. Sport - More info .... (pyce)*

Tidbit of information found on the Roehrig Engineering forum. (Roehrig has shock dynos)
As quoted from their site, pertaining to oval track racing. "The body roll that effects handling is going to be below 10ips. (in the 2-6ips range I think)"


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## Ceilidh (Jan 7, 2004)

*Re: Bilstein HD vs. Sport - More info .... (kevinstillwell)*

Hi Kevin,
Thanks for the datum point! Would you know what's a typical roll rate for a circle track car? Or failing that, what a typical circle track roll angle is? If the roll angle (degrees per g) is roughly a third that of a stock Golf/Jetta, that'd put the Golf/Jetta peak piston velocity in roll at ~18 in/sec....... but I'm not familiar with circle track parameters.
Thanks again!


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## pyce (Nov 7, 2001)

*Shim Program Help ..... kevinstillwell*

Kevin, please help me here!
I have this stack:
14 x 5,5 x 0.1 (Bleed Washer)
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.1
14 x 5.5 x 0.1
8 x 5.5 x 0.6
Screw Head
Now, I input this in the Shim Program on top and put the 8 mm washer in the bottom where you suppose to input the screw head. The washer is so thick, so it acts like larger screw head, right? Then I "copy" the stack to the right on the screen and then change that 8 mm washer to 11 mm (1 mm thick) and guess what happens? The software gives me an increase from 575% that grows to above 600% for the bigger deflections (!) Now, those are some crazy numbers and do not fully match the results I am getting from the dyno and most of all, from the street. The stack with the 11 x 5.5 x 1.0 washer on top (instead of the 8 mm) works really well on the street, with no preload gives a very nice bump-hit feel and it has fantastic high speed, the car stays "on top of the bumps" at all time! ...... My question is: Where do I make the mistake in the input on your program, so it gives me these crazy 600% results which I am not any near in real world? Thanks a lot! 
I still owe you huge reply for the least few posts of yours, but I have very, very limited time for these experiments nowadays, and I rather use it in the shop. One day soon, thought, I will not sleep one night and will reply to you! Thanks for your help!


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## kevinstillwell (Feb 28, 2005)

*Re: Shim Program Help ..... kevinstillwell (pyce)*

Ceilidh,
I don't know about the roll rate. I got the tidbit of 2-6 ips from the Roehrig dyno forum, and they did not go into details.
Peter,
First, we need to define the base shim. If the bolt acts as the base shim, then we need the exact diameter, and if the bottom of the bolt is angled.








Second, does the first stack have preload?
Third, what is the dyno showing for differences. 
With this info, we can decipher what the program is doing.


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## pyce (Nov 7, 2001)

*Re: Shim Program Help ..... (kevinstillwell)*


_Quote, originally posted by *kevinstillwell* »_First, we need to define the base shim. If the bolt acts as the base shim, then we need the exact diameter, and if the bottom of the bolt is angled....

Kevin, the bolt has about 7 mm head, but I did not consider it as "base shim" as the washer below the head is very thick, so I figured out it would not flex at all, therefore I input those washers (the 8 mm first and 11 mm later) to be the "bolt head". Here are again both stacks for you. In bold the changes I made:
14 x 5,5 x 0.1 (Bleed Washer)
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.1
14 x 5.5 x 0.1
*8 x 5.5 x 0.6*
Screw Head (7 mm)
14 x 5,5 x 0.1 (Bleed Washer)
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.1
14 x 5.5 x 0.1
*11 x 5.5 x 1.0*
Screw Head (7 mm)
Basically, to me (but maybe here is where I am wrong) the 8 mm washer first and the 11 mm washer later, act like screw head, aka base shim, as they virtually do not flex, as does not flex the screw. To me it is like if on top of all the 14 mm washers I used once an 8 mm screw head and then 11 mm screw head...... is that correct?

_Quote, originally posted by *kevinstillwell* »_Second, does the first stack have preload?.... 

No preload in either stacks! From this page on there will be no preload in all experiments. For my tastes, the preload is enemy number one when it comes to street comfort, so there will be no more preload!









_Quote, originally posted by *kevinstillwell* »_Third, what is the dyno showing for differences.....

The graphs I can not show you now as I am unable to do anything from the place I am. But here is an old graph that shows what the first stack does (the one with 8 mm washer). Look at the curve that says "V1.3 Revalved":








Now, the second stack you have to imagine, (with the 11 mm washer) does the same low speed, but it raises gradually at the high speed, reaching let's say the 150 lb mark in the above graph, but very smoothly, very gradually.
So, what I was expecting to see in the shim program (and that is why I am convinced that I screw the input somehow) was some sort of almost 0% for the first few values of deflection, then slowly to see some 5%, then 10%, etc.... and to get some 15-25% for the highest deflections. At least that is what the dyno shows should be........ So, what do you think, why did I get some crazy 500-600% from the software? Thanks a lot!


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## pyce (Nov 7, 2001)

*Velocities .....*


_Quote, originally posted by *kevinstillwell* »_Two things are being guessed at, and need to be nailed down (or at least come up with a close approximation).
*1. Velocities - What are the actual velocities of the damper on the car for various type bumps.*
2. Deflections - How much are the shims actually deflecting? It sounds like Peter's next test will help determine this.

Winston, can't we get the velocities from the accelerations? I can put the accelerometer right on the damper, instead of the trunk like for our previous experiments, so we can get the real damper (wheel) accelerations. Then I can put it back in the trunk and do some slaloms, etc, so we can determine more or less the velocities that control roll...... what do you think?


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## pyce (Nov 7, 2001)

*Re: Thoughts from a Guru (2beirish)*


_Quote, originally posted by *2beirish* »_..... So does Boge make a set of dampers for MKIV chassis cars we could incorporate into this thread?









It was in the plans. I contacted a vendor (there is a note about this on some of the early pages here) and have been told that the Boge "Automatics" were not yet available for the A4 platform here. There were no other dampers that they could sell me for this car. 
I do fully agree with what Jim Rowe told you. The feel on the road is like with pre-loaded stack and now the dyno graphs (which you all are going to see soon) are proving it too. 

_Quote, originally posted by *banjomike* »_ ....At some point along the way I went to the Bilstein website and I looked up the part numbers for the dampers that they make for the mkIV platform. I noticed that the same part number applied to the Golf, Jetta, and NB. I got curious so I did a search for those part numbers to see ho many different cars they sell that particular damper for. I only came up with one other hit. The Audi TT. Which got me thinking. What dampers does Audi put on the TT from the factory? Does the TT have a standard and a sport suspension? I wonder if the stock shocks from a TT might not provide a decent ride and last longer than the standard fittings on a lowly Golf? 

I will try to find a TT front damper and dyno it. It may as well be a great "sporty and comfy" solution for a Golf/Jetta/NB! If nothing else, we can try to revalve a front Koni to match the TT values and see what that gives. Thanks for the insight!


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## Ceilidh (Jan 7, 2004)

*Re: Velocities ..... (pyce)*


_Quote, originally posted by *pyce* »_
.....can't we get the velocities from the accelerations? I can put the accelerometer right on the damper, instead of the trunk like for our previous experiments, so we can get the real damper (wheel) accelerations. Then I can put it back in the trunk and do some slaloms, etc, so we can determine more or less the velocities that control roll...... what do you think?









Hi Peter,
The second half of your suggestion might work (good thinking!); the first half might be more difficult:
1) Roll Velocities:
Yes, if you the sensor directly above the shock mounting point (to record the chassis vertical acceleration at one wheel as the car rolls), we can integrate the acceleration profile to determine the velocity curve.
However, we'll have problems if the vertical acceleration is small compared with the lateral g-forces: in that situation, small errors in mounting alignment (plus ensuing vehicle roll) will give us an error term that will be very hard to filter out (at least with the current equipment). But if the vertical accelerations turn out to be large, this error won't be too consequential....
2) Bump velocities
The problem here is that while the damper is accelerating upon the wheel hitting a bump, the car chassis is accelerating as well. If you had two accelerometers -- one on the chassis, and one on the wheel hub -- we could separate out the two effects. But with a single sensor, we can get reasonable readings only high-frequency bumps that don't move the chassis very much. (Though of course, that info alone might be interesting.)
In any case, don't go buying any more equipment until we've talked more about this! But do let me know if you're seriously considering doing these experiments.
Cheers!
- W


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## kevinstillwell (Feb 28, 2005)

*Re: Velocities ..... (Ceilidh)*

1. We use a ShockClock to measure velocities. It gives a good idea of the general velocities you are working with. If you are interested in measuring velocities, this would be one way to go. 
2. I need to clairfy the damper we are using. Is it the Koni Yellow, which is also = Koni Sport? And what is the tube design?


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## Ceilidh (Jan 7, 2004)

*Re: Velocities ..... (kevinstillwell)*


_Quote, originally posted by *kevinstillwell* »_1. We use a ShockClock to measure velocities. It gives a good idea of the general velocities you are working with. If you are interested in measuring velocities, this would be one way to go. 


Hi Kevin,
That's a very nice data acquisition system! But the retail price is ~$800 ; is there anyplace that might rent one out to Peter?
Peter, if the answer to the above turns out to be "No", I'll look into other (less ideal) possibilities for you.
Cheers, both of you!
- W


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## pyce (Nov 7, 2001)

*Re: Velocities ..... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_ ...Peter, if the answer to the above turns out to be "No", I'll look into other (less ideal) possibilities for you......

If could be rented, I am all ears! If I have to buy it, I rather spend 800$ in a different way. Or perhaps I can look for an used piece and then resale it? Let me talk to Phil as well. He just got this whole telemetry package (is a huge briefcase) that says "8 way acquisition data", so perhaps we can get one of those components to record speed for parts in movement. I know it has a gyroscope, so we will eventually one day get those roll angles.... let see what he thinks. Maybe we can buy together the 800$ stuff..... You said if this is "NO" then you would look into other less ideal possibilities? What would that be? I guess we do not have to be super precise with the velocities, we just need to be accurate enough so we know more or less which speeds are generated in which situations. I guess a 2-4 in/sec mistake is not a big deal in our experiments, at least not for now. Thanks Winston!


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## Ceilidh (Jan 7, 2004)

*Re: Velocities ..... (pyce)*

Hello Peter,
Well, for half the price (~$350), you could try one of these:
http://www.spaceagecontrol.com/s021g1.htm ; combined with:
http://www.dataq.com/products/startkit/di194rs.htm
but I would think that's too expensive too! I'll poke around and see if there's anything considerably cheaper.
In any case, I do think you could get some rough data via your original idea (of simply mounting the accelerometer to the shock body for motion over bumps, and of trunk mounting for motion due to handling maneuvers). That is, I didn't want to sound too discouraging earlier -- so long as you're only trying to get a rough idea of the piston velocities, there are ways around the problems mentioned earlier. Specifically:
1) On the bumps, you could look for a road that's bumpy, but which does not jostle the chassis that much (i.e., find bumps that are fairly regularly spaced, and drive at the "magic speed" that allows the chassis to seemingly float over them).
2) If the above turns out to produce unusable data, you can do some data processing on your raw accelerometer data. Unfortunately I'm not nearly as computer proficient as you are, so I wouldn't be able to implement it for you, but somebody in your company has got to be able to help out, if you give them the right key words (it's a very basic, straightforward data processing technique): just tell your resident techie jock that you want to "Apply a fast fourier transform to the accelerometer data; strip out all the components slower than 2 hertz (using a smoothing filter); and then reverse transform to get a new accelerometer curve that's missing the low-frequency information." (There are (probably free shareware) code packages that can do the preceding very easily; I just don't know what's available for a PC....) If you can do that, then you don't have to worry about the chassis motions.
3) For the roll data, you might get perfectly usable data by mounting the accelerometer on one side of the trunk and slaloming side to side on a smooth road. If alignment errors cause problems, just park your car across one of your San Francisco hills, tell me the angle of the hill and your accelerometer readings, and I'll send you a rough correction factor.
4) Finally, if you don't want to mess with data processing filters, etc., you might also consider simply buying a second accelerometer: for the bumps, mounting one accelerometer on the shock body and the other on the chassis will allow you to determine the vertical speeds of both shock & car; the piston velocity is then simply the difference between the two. You can also mount the second accelerometer sideways in the trunk for your roll experiments, which would give some interesting data for roll velocities at different lateral g, as well as for the relation between roll damping and steering response (i.e., how quickly the g-forces can build up vs. how tightly you damp the roll).
5) But of course, borrowing a nifty package from Phil would be the best.









Cheers!
- W


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## phatvw (Aug 29, 2001)

*Re: Velocities ..... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_
2) If the above turns out to produce unusable data, you can do some data processing on your raw accelerometer data. Unfortunately I'm not nearly as computer proficient as you are, so I wouldn't be able to implement it for you, but somebody in your company has got to be able to help out, if you give them the right key words (it's a very basic, straightforward data processing technique): just tell your resident techie jock that you want to "Apply a fast fourier transform to the accelerometer data; strip out all the components slower than 2 hertz (using a smoothing filter); and then reverse transform to get a new accelerometer curve that's missing the low-frequency information." (There are (probably free shareware) code packages that can do the preceding very easily; I just don't know what's available for a PC....) If you can do that, then you don't have to worry about the chassis motions.


I remember doing that stuff in MatLab. Hello 3rd year computer engineering








But even simpler, if you have acceleration, can't you just take the integral over time to get velocity? Or perhaps this impossible because, for all intents and purposes, the acceleration curve is discontinuous...


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## Ceilidh (Jan 7, 2004)

*Re: Velocities ..... (phatvw)*


_Quote, originally posted by *phatvw* »_
But even simpler, if you have acceleration, can't you just take the integral over time to get velocity? Or perhaps this impossible because, for all intents and purposes, the acceleration curve is discontinuous...


Hi Phat,
Absolutely! He'll be integrating to get velocity! The potential problem (i.e., the "unusable data" referred to above) is that the chassis might start bouncing up and down too, which will contaminate the acceleration data. Hence the suggestion to filter out the low frequency part of the signal, which (in an extremely crude way) will somewhat compensate for that.
In any case, borrowing equipment from Phil (or adding a second accelerometer) would be a better!


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## pyce (Nov 7, 2001)

*Velocities ..... and a New Base Valve!*


_Quote, originally posted by *Ceilidh* »_ ....In any case, borrowing equipment from Phil (or adding a second accelerometer) would be a better!









Winston, sorry you had to type all those nice solutions! I was unable to reply to you earlier, but met with Phil tonight and he has all the stuff we need for this! We just need to do some hardware as to attach his equipment to the car's damper and we are good to go. He has this "device" which I do not know the name of, that looks like mini-damper itself, like those we have on the trunks, even smaller in diameter. We have to attach the body to the damper and the shaft to the car and that thingie will give us directly the velocity in time! I guess this may as well be the Shock Clock that Kevin was talking about, I just did not ask Phil what is that called. So, that is to come, but it may not happen so soon. I have very limited time, but will try my best as this information is essential for our experiments....
Kevin, I gave you some information about the two stacks in an earlier post. I am afraid that you may have not seen it as there were three posts in a row I did that night (towards the last part of page 11). Let me know if you need more info from me for that answer. Thank you! ...... Oh, and by the way, yes, we are using Koni Yellow (Sport), which is a twin tube and it had been "pictured" and modeled (at least the base valve) few times on earlier pages. I can give you more data about it if you need, just let me know.
By the way, as of today, the base valve is very different. We filled up all the 10 holes that flow the oil towards the washers and made only 3 new holes, with diameter 1.45 mm each (the old holes were with diameter of 1.75 mm each). There is also no more possibility for even the slightest pre-load as we flatten the surface where the washers sit, so they sit right on top of the three holes now. I will make some pictures tomorrow, so it is easier to understand what we did. Phil said that the existing base valve was unable to help is to get good high speed with very soft low speed, so the new valve will take care of the high speed (from the experiments with the restrictor-washer we kind of guessed the optimal flow for the new valve, therefore the 3 small holes) and then with the washers we can go very "thin", as to get a very nice soft initial opening at the low speeds. Basically, he wants to separate the tasks and make the valve do the high speed, so this way to get a more "detailed" and refined low and mid speed stack only. We will see what that gives tomorrow..... Good night.


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## kevinstillwell (Feb 28, 2005)

*Re: Shim Program Help ..... (pyce)*

Hi Peter,
Sorry for the long delay. I've been busy bumping my head and smashing fingers in an attempt to get our new track-side support truck built.
This is in response to the Shim Program comparison between the following stacks. You were suprised to see a 600% increase in loads between these two stacks. (the second stack being the stiffer)
14 x 5,5 x 0.1 (Bleed Washer)
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.1
14 x 5.5 x 0.1
8 x 5.5 x 0.6
Screw Head (7 mm)
------vs---------
14 x 5,5 x 0.1 (Bleed Washer)
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.1
14 x 5.5 x 0.1
11 x 5.5 x 1.0
Screw Head (7 mm)
There are several things to consider when analyzing shims via the program. 
1. The program is calculating the stiffness of the shims. A 20% increase in shim load, for example, does not translate to a 20% increase on the dyno. If the ratio was 4-to-1, a 20% change on the program may only show a 5% change on the dyno.
2. Without knowing the exact increase for the two tests in question, I can only speculate. From your description, (I know this is approximate) the maximum force on the dyno increased from 90 lbs to 150 lbs, or about a 166% increase. Refering to #1, we know that a 500% increase in shim loads will not = a 500% increase in the dyno. (i.e. The dyno did not jump from 90 lbs to 450 lbs).
3. Since the dyno graph looked similar at the beginning, you expected the program to show close to 0% increase for the beginning deflections, and then have the % increase as the deflections increased.
With the force-displacement graphs, we must remember that both graph lines start at 0. So the initial part of the graph may look similar, due to scaling, even thought there could be a rather large %change. 
At the lower deflections on the program, the loads are very small. A 200% increase (2x) seems large, but the actual lbs change is smaller. 
e.g. At a lower deflection in the program, the load may go from 15# to 30#. A 200% increase, but an increase of only 15#, never-the-less. At the higher deflections in the program, the load may go from 200# to 400#. Also a 200% increase, but an increase of 200#. 
So, it is all a matter of intrepretation. If I am viewing the % increase from the program, I want to compare that to the % increase from the dyno. The force-displacement graphs we are viewing are not making these types of comparisons.

_Modified by kevinstillwell at 8:52 AM 4-8-2005_


_Modified by kevinstillwell at 8:55 AM 4-8-2005_


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## pyce (Nov 7, 2001)

*Important (giant) step ahead!*

.... Today had been maybe the most important day since our experiments started! We got many answers and the whole project made an incredible turn in the right direction. There is so much that needs to be said about today's discoveries, but I am unable to go in depth right now, so will give just the highlights and later on we will talk in depth......
1. Kevin, I think to have found the main reason I could not get reliable prediction from your program! Basically I always ignored the fact that the damper we are using has a bleed washer, which the program does not account for! I always thought that a bleed washer of only 0,1 mm thickness and tow very minor bleeds would do close to nothing when the whole stack gets going towards the high speed, so I completely ignore it and that was my mistake number one, because this is what we found today:
2. The small, thin, little, innocent bleed affects the whole high speed (and mid too!) in an incredible and unbelievable way! That whole concept about having a bleed has been the most misleading thing in our experiments, because I basically never took it off and never consider it as such a major player in preventing our goals (to achieve linear or even progressive curve).
3. No matter what stacks we used, there is no way to get a curve with no "knee"! Basically, I am going to shoot high here and say a big word, but I think that using a bleed can lead to only digressive valving! Sure, you can do then something to increase the high speed, but guess what happens? You get then a "knee"! So, basically:
4. If you start with soft washers to get a nice initial part of the curve (nice smooth low speed), then the high speed really goes flat - there is no high speed that is.
5. Then you start adding thicker washer (smaller diameters) on top of the initial soft washers, as that improves high speed.... and in fact the high speed comes, BUT for small improvements in the high speed you get much more pronounced "knee" in the low-to-mid speed. 
6. This is (Kevin) primarily why we got the crazy % numbers from your software, but could not see them through the dyno - because the bleed screws up the whole concept behind the shim program! Basically, those those stacks I was telling you about earlier were really 600% apart, but we could get the dyno to show it only when the bleed was removed! (Thanks for the earlier post, it is very clear that I misunderstood the way those percentages apply to the whole game! In fact, on some of the earlier pages, where I describe how your software works, with some graphs, I have been totally wrong, as I presented the percentages as variation on the dyno curve, not on the shim load! I guess some time later I have to edit those posts and correct them as the mistake is very bold. Thanks again, I think it is now clear!).
7. Basically it comes down to this - the volume of oil in this specific damper, that is tested at 2" of travel, at speeds from 2 in/sec to 30 in/sec is quiet smaller than what I was imagining, so even a super small to the human understanding bleed, would cause an incredible amount of "leak" and will basically prevent the whole stack to work as intended. You can spend a week of "designing"a stack using the shim program, and as long as it has a bleed washer in there - is never going to work even near to what you thought! 
8. The bleed was also the reason we could not achieve the FiBoL curve! The oil that goes through is so little, that the bleed holes take care of major part of it to go through, leaving very little for proper washer deflection, which deflection had never been enough to even touch the thicker washer for the 2-nd stage! 
9. In few words - you take out that bleed washer from the same stack I was talking about above and then reduce the number of the other washers too (as it now has to be very, very soft initially as to open easy and smooth, we do not want "knee") and the curve comes like a dream! Here are the two stacks:
A - old stack that was showing 600% gain in shim load, but was very disappointing on the dyno:
14 x 5,5 x 0.1 (Bleed Washer)
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.2
14 x 5.5 x 0.1
14 x 5.5 x 0.1
11 x 5.5 x 1.0
Screw Head (7 mm)
B - new stack that really got us dyno numbers we have not seen yet!
14 x 5,5 x 0.1
14 x 5.5 x 0.2
11 x 5.5 x 1.0
Screw Head (7 mm)
I do not have the possibility to show you the dyno curve from this latest "B" stack (this is Revalved V4.2 by the way), but look at the highest black line (the 30 in/sec speed) from the following diagram:








Basically with the shim "B" we got the exact same shape, but instead of peaking at about 130 lb (like on the above graph) it peaks at above 200 lb (!) so the curve looks closer to a circle than to an ellipse, which the above is. The force vs. velocity looks like a perfect straight line, it was such a beauty to look at! First time ever we managed to get no knee!








10. Phil was saying that it is bad idea to run only two thin washers with such loads, as they will flex way too much and in few thousand miles they may break, so now the next step would be to:
a - First lower little bit that 200+lb value of the high speed as it is too high (nigher even than the original Koni Yellow!), but absolutely maintaining the shape of the curve!
b - Second, to use only 0,1 mm washers, so this way many would be stack on top of each other, which Phil says will help them to survive longer. The shim program will tell us how many, but I guess we will start with at least 7-8 of them instead of the one 0,2 mm we have right now.
11. This whole thing brings a very new perspective on how exactly the original Koni Yellow and Red work, but we will talk about it in a different post later.
12. Bleed perhaps is not a super-bad thing when it comes to comfort, so after trying these no-bleed configurations on the street, we may as well come back to having bleed again, BUT this time we will make it much smaller and will try to find out where is the boundary, where it becomes "too big" and keep it just around that boundary.
13. The base valve had also been modified twice today, we got some observations there too, but that is a new post as well, as it absolutely needs renderings, otherwise I have to type till tomorrow and still may not be able to be clear.....
Ok, so much for tonight. I am not entirely sure that everything I said is truth, but the results are where we wanted to get, so I guess there must be at least some truth to what the theories are.







More later.....


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## BAMA TDI (Nov 26, 2002)

*Re: Important (giant) step ahead! (pyce)*

Peter,
I have been keeping up with this thread with great interest. What you and everyone else had done and are doing is fantastic. However comma as I e-mailed you the other day, my time ran out. I had to replace tires and suspension. You asked me to let you know how I like my set up. Well after a week I can say it's what I wanted. http://****************.com/smile/emthup.gif The car is really firmed up but not too harsh. I went with Bilstein HDs front/rear, sport springs, H&R 28mm rear sway bar, and urethane bushings. I am VERY pleased with both handling and ride. Now in certain right hand bends on the local I-state system here, the Social Director aka wife is not ending up in my lap anymore.







There is a road coming into the little town where we live that bends to the right.
Just as you come into right hand bend there is road branching off to the left. I used to take that road to the left sometimes and nail the throttle. It has a dip in it that makes you feel like you are on a roller coaster. Our car started to bottom sometimes. I took it yesterday as the final acid test for the suspension. No bottoming out whatsoever. It was great. Wife gets a kick out of it when I take this way. As for the tires I followed a friend's recommendation and went with Kumho KH11s. These tires are fantastic in the rain. We have been getting soaked here off and on the past week and no hydroplaning. Very cool.
Like I posted at the beginning you and everyone keep up the great work.







http://****************.com/smile/emthup.gif







http://****************.com/smile/emthup.gif







http://****************.com/smile/emthup.gif


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## Ceilidh (Jan 7, 2004)

*Re: Velocities ..... and a New Base Valve! (pyce)*


_Quote, originally posted by *pyce* »_
......as of today, the base valve is very different. We filled up all the 10 holes that flow the oil towards the washers and made only 3 new holes..........then with the washers we can go very "thin", as to get a very nice soft initial opening at the low speeds......

Hi Peter,
Bravo! I didn't realize you had already started on the new base valve -- it's probably a little late, but here's some of the other info I alluded to earlier, but hadn't got around to explaining. To wit:
As mentioned earlier, I had time to think more about the damping on my recent drive back to Boston, and I'm thinking that -- just possibly -- the flow patterns within the shock absorber might have a signficant impact on ride comfort. And thus, as the base valve has a big effect on these flow patterns, it's possible for you to improve or degrade the ride comfort via changes in the valve configuration.
The best way to visualize the issue is to pretend you have a shock where somehow (i.e., it's almost impossible to make a real one that does this, but let's just pretend....) the orifices that admit fluid to the compression valves are the same ones that permit fluid to exit the rebound valves -- i.e., pretend you have a valve design where fluid going through a passageway has to reverse direction when compression changes to rebound (or rebound changes to compression).
Given the above "perfectly awful" valve design, picture what happens at the end of the rebound stroke (i.e., when the car's just come off one bump and is beginning to encounter a new one): the shock fluid has been running through the rebound valve at high velocity, and that flow has set up a large scale circulation in the shock body as a whole. That circulation has inertia. When the compression begins, the flow within the passageway has to reverse. When it reverses, it begins to draw in fluid from the overlying shock body, which in turn has to reverse the circulation pattern that was set up by the rebound motion. In effect, this circulation pattern "fights" the initial opening of the compression valve: the compression valve is trying to draw in fluid that's initially flowing in the opposite direction, and thus less fluid is able to pass than would in steady state. The result is ride harshness: the inertia of the fluid acts in the same fashion as a temporary valve preload, requiring that an extra amount of piston force be exerted to overcome the inertia. Once this inertia is overcome and the fluid's flowing in the right direction, the effect disappears and the valve effectively "softens". Hence you have the worst of both worlds: the shock resists reversal, meaning that it's very harsh on high-frequency bumps and in initial bump impact, but it softens up for big, sustained shock movement such as that produced by chassis motions or by jump landings.
In contrast, imagine a shock whose rebound valve-exit sets up a large scale circulation (e.g., a vortex) in the fluid, but which has the entry port for the compression valve situated directly in the path of the circulation return flow (i.e., the rebound valve-exit pushes the fluid away in a big circular path, and the fluid flows around and sweeps back towards the compression entry port). For this hypothetical shock, no flow reversal is necessary when the shock switches from rebound to compression. During rebound, the exit flow excites the flow; during compression, the intake flow maintains it. This shock should have very smooth reversal behaviour: at the beginning of the compression stroke, as the compression valve first begins to open, fluid is actively pushed through the pre-existing return flow without any need for extra piston force.
Such a shock will not only have smooth reversals, but its ride should actually seem to "soften out" on a prolonged series of bumps. That is, the first bump encountered has to get the flow moving (i.e., it has to overcome the inertia of the initially stationary fluid), but after that, every bump kicks the circulation a little faster, which in turn makes the reversals a little more immediate, and hence the ride harshness goes down.
In any case, when you experiment with the valve bases, you might wish to (as you're probably already doing) keep track of two things:
1) The first is to ensure that the fluid has a smooth flow path, without hard corners or sharp obstructions to overcome on the way towards or away from the actual valve discs.
2) The other is to visualize what the flow upstream and downstream of the valves will look like under both compression and rebound, and to organize the geometry of the orifices/bypasses/etc. so that both compression and rebound will set up the same circulation pattern in the main fluid reservoirs (or alternatively, set up something like the Boge-Sachs captive donut-vortex described earlier). In practice, I'd imagine that that you can easily set up a flow circulation that flows vertically (upwards or downwards) along the inside wall of the shock, and then vertically back in the opposite direction (downwards or upwards) at the center of the reservoir/along the outside of the piston shaft. If you can do that (which might entail, for example, putting the rebound exits at the outside circumference of the valve and the compression intakes closer inboard), you might be able to smooth out the ride somewhat.....
Anyway, just some thoughts.










_Modified by Ceilidh at 8:16 PM 4-10-2005_


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## kevinstillwell (Feb 28, 2005)

*Re: Important (giant) step ahead! (pyce)*

Just to make sure I am following correctly, I'm assuming the comments [subject: Important (giant) step ahead!] are pertaining to your newly modified piston with 3 holes instead of the original 10. In addition, it sounds like you modified the piston in such a way that the shims sit directly on the holes. 
I am not able to visualize the exact piston changes. A photo would be most helpful.
In the late 80's, I spent hundreds of hours testing piston designs with many different combinations of orifice size and configurations. There is definitely room for change in this area.
Also, pertaining to your bleed washer. You are correct in stating that the volume of oil was very small. Without knowing the shaft diameter, here is an example. If my calculations and conversions are correct, if the shaft diameter was 5/8 inch, the volume of oil passing through the foot valve at a 2" stroke would be about 1/3 of an ounce.
Area of shaft = (.625/2)^2 x pie = .307 in2.
Volume of shaft = .307 in2 x 2" = .614 in3.
Convert .614 in3 to ounces = .614 x .5571 = .342 oz
I'd appreciate any corrections if the above calcuations are in error.



_Modified by kevinstillwell at 4:48 AM 4-12-2005_


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## pyce (Nov 7, 2001)

*Re: Important (kevinstillwell)*

Kevin, you are absolutely correct! I am more a "millimeters" guy, so the shaft is 12 mm diameter, and basically the oil displaced is the volume of that shaft for the 2" of stroke........
I am sure some of the folks are not quiet sure what you are talking about, so let me explain little bit as to be clearer. I assume some are asking themselves "Why a 28 mm piston moves down 2" displaces the amount of 12 mm cylinder?"..... Well, in this damper design, then the piston moves down, there is a large hole in the piston itself that allows the oil to flow above the piston, in what is the rebound chamber (let's call it that way as I do not know if that is correct). Basically, once the piston is done going down for the compression, it has to have full tube on top as to get good rebound stroke. So, the piston goes down, but there is free flow to fill up the top. But the top has the shaft, the bottom has nothing! Therefore, the oil that could flow in the top chamber is the same from the bottom chamber, less the volume of the shaft. That is why, in a way, the bigger the shaft, the more oil the damper displaces, the more efficient the damper could be (for the given design, valving, etc). Seeing a drawing would make it much easier, but there is no possibility for me now. Perhaps in two weeks time, lots of drawings and graphs will come...
Winston, Kevin .... as for the foot valve, Phil suggested to make the bed completely flat, so these three holes we made to act directly on the shim. But then I was afraid that we would not be able to use the shim program correctly again (as there is this "pof" in the upper left corner of the screen that if I am not mistaken takes in consideration the diameter of the lower lip, where the oil lifts the stack, right?) and if we have no "chamber" below the stack, what do I type in that "pof" area? (By the way, do you call that "point of flow" or what is it that "pof" stands for?)....... Plus, I thought (but could be wrong) that by "connecting" the three holes with some sort of a chamber, the oil will act on the whole circumference of that chamber and the washer, so the operation could be smoother, but of course I could not be sure of that.
Ok, let's go back little bit and talk about the three holes we made (instead of the 10). I do apologize, there is no picture for the moment, neither drawings, but it will come soon! For the moment, just try imagine, looking at the existing valve here:








Let's start from the very center, so it is clearer what we did. You see there the hole for the screw. Then then next thing you see around are those small ten holes, where the oil flows as to fill up the "chamber". The holes are 1.75 mm diameter each. The chamber is 12 mm diameter and 0,75 mm deep. We filled up all this, re-drilled the hole for the screw, then drilled three new holes, each has diameter of 1.45 mm and are placed as the old ten holes were, on the same virtual diameter around the screw. Now, imagine a donut, actually imagine a sliced in two bagel! That is the section of the mini "chamber" that connects the three holes. The outer lip of that bagel, where the oil flows from, is 12 mm. Decided to go with 12 mm as to see what the new valve gives if we have the same "pof" and same stack. Now, the other thing that the "bagel" did is to create a small inner platform around where the screw is, so we can screw the stack all the way down and be sure there is no preload at all, as the surface is the same inside of the "bagel" and outside. Then on the existing valve you see another "lip" next to the first one. We took that one out. Well, basically, moved it more outside, closer to the outer 18 holes that let the oil flow back in the tube after compresison. That pretty much is the "new" base valve.....
Now, let me just say that the new three holes (diameter 1.45 only!) are still super big







We did not get any high speed from there, basically just restricting the flow by this much did not do a thing! This was actually the main reason that made me stop for a second and calculate the oil that flows during those 2" of stroke, because I was amazed by how little those three holes are and still they could not restrict the flow even for a second. So, next step would be to fill those holes and leave only one of them, then perhaps slowly make a second on (or enlarge the first) as to catch what is the size that makes some controllable difference for the high speed.
The idea behind this valve is that there will be 7 to 8 thin washers (0.10 mm) as to have great low speed, smooth opening, etc. and let the holes on the base valve to take care of the high speed. This is basically what Phil calls "Old Motorcycle Design", but according to him it works great for what we are trying to get. Before that, thought, I am interested to leave the three holes for a week and see what could be achieved with just washers. We have already done some modifications to the stack, and must say that for this valve design, no bleed, no preload - the shim program works fantastic! Everyhting that the program showed to us, came out from the dyno the same! So, at this point I would like to spend some time to just input as many configurations as I can in the program and see what each of them give. Basically, Phil says that you can have 20 dampers that have 20 different valvings, but set in a way that show the same dyno curve! Now, according to him, all 20 will ride very differently when it comes to feel for the driver. My goal is to get few settings (via the shim program) that will give me the same curve I have now, then dyno those few configurations and then drive them for some time, so to put feelings on what he said.....
Winston, thanks for the suggestions on the foot valve design! I think we are not any near the stage where your refined ideas would apply. But one thing is for sure - when the time comes to refine the final design, you will be the lead! http://****************.com/smile/emthup.gif


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## Ceilidh (Jan 7, 2004)

*Re: Important (pyce)*

Hi Peter,
Nice work!








Just a quick note: depending upon the precise geometry & size of your "donut", it's possible you might find your damping to be a little firmer than predicted by the programs, particularly at higher speeds. (But I'm just going on your written description of things....) In any case, do keep us posted whenever you have time!
All best,
- W


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## pyce (Nov 7, 2001)

*Two Tea Spoons we are deling with here.......*


_Quote, originally posted by *kevinstillwell* »_ ..... Also, pertaining to your bleed washer. You are correct in stating that the volume of oil was very small. Without knowing the shaft diameter, here is an example. If my calculations and conversions are correct, if the shaft diameter was 5/8 inch, the volume of oil passing through the foot valve at a 2" stroke would be about 1/3 of an ounce.
Area of shaft = (.625/2)^2 x pie = .307 in2.
Volume of shaft = .307 in2 x 2" = .614 in3.
Convert .614 in3 to ounces = .614 x .5571 = .342 oz
I'd appreciate any corrections if the above calculations are in error.....

As said in the earlier post (you cold not know it before), the shaft we have (Koni Yellow Sport) is 12 mm, which converts in 0,472", which is quiet less than your 5/8" example, so our situation looks even worse







Using your formulas, but with the new number, we have:
Area of shaft = (0,472/2)^2 x pie = 0,175 in2
Volume of shaft = 0,175 in2 x 2" = 0,350 in3
Convert 0,350 in3 to ounces = 0,350 x 0,5571 = 0,195 oz (this is about 5.7 milliliter!)
To give an idea what volume we are talking about here, the Koni Yellow oil displacement for the 2" stroke is nothing more by precisely *two not-full to the top tea spoons*!!!


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## pyce (Nov 7, 2001)

*Re: Velocities ..... and a New Base Valve! (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_
...... The best way to visualize the issue is to pretend you have a shock where somehow (i.e., it's almost impossible to make a real one that does this, but let's just pretend....) the orifices that admit fluid to the compression valves are the same ones that permit fluid to exit the rebound valves -- i.e., pretend you have a valve design where fluid going through a passageway has to reverse direction when compression changes to rebound (or rebound changes to compression).
Given the above "perfectly awful" valve design.......

Winston, the funny thing is that I saw one damper exactly like this, just the other day!







Phil has few RC, and of course, you guessed it right, he revalves those things too, LOL! Here is what the suspension on that RC looks like:








So, I was watching him taking apart the dampers, as the RC was bottoming when landing after a big jump, so he wanted to make them stiffer. Once he opened the damper, what do you think it is there? Basically the damper you describe! There is a shaft, at the end of which there is a small round plate, which is "the piston" and on that piston there are two mini-holes and that is it. This thing goes up and down in the tube and the oil flows from one side to the other through the same holes. The "revalving" he did was nothing else but to eliminate those holes and make a new one, only 1 mm diameter, so less oil was going through, and that is it!







The result? You could lift by hand that whole RC above your head (basically as high as you can reach above your head) and drop it on the floor ....... the darn thing, believe it or not, did not tough the floor with the chassis! ..... and after that did not even bounce back! It landed as it would land a pillow from that height. Absolutely amazing!
The sad part ...... that RC almost-toy-damper displaces more oil during its normal operation than the Koni Yellow for our 3.000 lb cars when moves 2"! LOL.


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## rracerguy717 (Apr 8, 2003)

*Re: Two Tea Spoons we are deling with here....... (pyce)*


_Quote, originally posted by *pyce* »_To give an idea what volume we are talking about here, the Koni Yellow oil displacement for the 2" stroke is nothing more by precisely *two not-full to the top tea spoons*!!!








WOW thats small about . Now i know why they build in external adjustment for when the shock breaks in and performance falls off a small about







Bob.G


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## supersonico (Aug 10, 2003)

Peter, I´m almost sure you´d be surprised to know that there actually are externally-adjusted dampers in the RC world







there used to be (I think there still is) this 4wd .15-2t powered touring car made by Serpent, whose name I can´t remember, to which you could do almost the same thing as your Koni Yellows or Reds... you´d take the "plunger" and twist it a few quarters of a turn, and every time you did that you´d clear a different-sized piston hole... I´m guessing that shims for different compression/rebound damping have probably already arrived at the RC scene, I´ve actually heard and read people *complain* about that technology not yet existing... come to think about it, it wouldn´t be that hard to implement. RC cars were pretty important to me, they helped me understand the principles behind suspension implementation with live examples I just couldn´t achieve in real life, and without the aid of a specialized book.
anyway, let me say a BIG thank you to yourself and to every other poster to this topic and forum, as people have correctly pointed out these are some of the most informative threads on our cars to date on the whole forum. keep it up, I´ll be watching!!!


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## pyce (Nov 7, 2001)

*The New Base Valves ....*

Things are looking little bit better here, so I will be able to (finally!) give you all the pictures, graphs, models, etc for the last month and a half of discussions. It is all going to be very mixed, but there is no other way I can do it. We already had the talks, now it is just the visual part, so to make sure we are all on the same page.
Let’s start with the Base Valve. We went through several modifications so far, but here are the main two new directions and small write up about them….
Below is not a complete model of the Koni Yellow Base Valve. Not the entire model shown as the parts that go below (few washers that cover the return-flow holes and few other things) are not so important for now. Let’s concentrate on the part where the compression stack goes. There is also a section and with two red arrows is shown how the oil goes into the chamber. For the records, those are 10 holes, with diameter of 1.75 mm each. Here it is:








Now, here is the first modification we did to the Base Valve. As you could see from the section, the entire middle part of the valve was filled and then worked in a way that first of all, takes care fo the pre-load elimination! In the way the valve it is, we could go pretty hard on the bolt, tighten it to the end and still there was no pre-load. That part brought very good level of consistency between the dyno sessions. Second, as discussed earlier, we wanted to kind of “restrict” the high speed flow, so the 10 holes (1.75 mm diameter each) became only 3 holes, with diameter of 1.45 mm each). Huge restriction, we thought, but it came out that is absolutely not enough as it did not do anything more than what the washers were doing. Basically, the idea was to have very soft washers as to get nice smooth opening and soft low speed and then “choke” the flow with the small holes when it comes to the high speed, so the washers are no longer in the game….. but it dod not work as those three holes were way too big for the miserable amount of oil (for the given speed) that had to go through. Here is that Base Valve V1.0:








The good part is that with this V1.0 valve and some simple stack, we can achieve a very linear compression, which was what I wanted to try on the car as to get a feel of what it gives. Here are the three curves we are after:








The Blue curve (this is all Force vs. Velocity) is what the popular off-the-shelf aftermarket dampers give us. The Red curve is what this particular Base Valve 1.0 gave us, but I am fully aware it is not because the valve has something “special”, but because we eliminate the bleed washer and did several versions with different base washer and also used what Phil calls “linear stack” which is basically several washers on top of each other with the same diameter. Fact is (and I will post those dynos later), the curve is like the Red line on the above graph. I would like to go after the Orange line, which is what we have been calling a “progressive” damper, where the force will increase more and more with the increasing of the speed, as to look like the Orange line. Curves like this work very well on some bikes, at least Phil says so and I have no reason not to believe him. I am just curios what would a damper like that be on a car. Please, do look at the above three curves as “concept” curves, not as actual. I mean, do not get scandalize by the very high value of the high speed, that is not where we are going. This is just to compare shapes for the moment, so you all understand what I am trying to say.
So, Phil said that it would be impossible to get the Orange curve with the Base Valve V1.0, as we have to use even softer washers and no matter how great we could guess the thick base washer on top, it is not going to raise the curve this fast and this high with simply the stack. He said we had to restrict the high speed flow and get the fast vertical acceleration of the curve from there, leaving only the very beginning of the curve on the soft washers. Therefore a new Base Valve (V2.0) came out. This time only two holes were made, 1 mm of diameter each. This time the washers sit directly on top of the holes, which is a method Phil is very familiar with and knows how to tune well later. Having two holes instead of four (common valve for many bike dampers) is going also to give us more flex of the washers, which translates to easier flex, if everything else is equal, which will give us even softer and smoother low speed. Here is what the Base Valve V2.0 looks like:








The valve is completed and mounted, but we did not have time to dyno it. Hopefully it will happen tomorrow. Let’s see what that will give us.


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## Ceilidh (Jan 7, 2004)

*Re: The New Base Valves .... (pyce)*


_Quote, originally posted by *pyce* »_......a new Base Valve (V2.0) came out. This time only two holes were made, 1 mm of diameter each......the washers sit directly on top of the holes.....Having two holes instead of four (common valve for many bike dampers) is going also to give us more flex of the washers, which translates to easier flex, if everything else is equal, which will give us even softer and smoother low speed.....

Everything makes sense, Peter.







So you'll bend the washers in 2-D, like a potato chip, instead of in 3-D, like a cone? -- a very clever way of softening the rate!
I very much look forward to hearing how a mildly progressive damper works on the open road. Strongly progressive dampers (what you'd achieve with simple orifices without any valving at all) were abandoned long ago on passenger cars, but I've heard tales of mild progressives used on some OEM suspensions; my experience is only with digressives, however, so this'll be interesting news to me!
If I can find some time this weekend, I'll try to work out some rough estimates of wheel/shock velocities in different situations; I used to think that we had to blow off the high-speed compression to be soft on chatter bumps, but last month's calculations of impact speeds on jump-landing (plus Phil's continued insistence that progressive compression is the way to go!) have made me wonder: perhaps the "sharp road bumps" that we'd like to soften actually occur in association with relatively low piston speeds, in which case your/Phil's progressive curves would make a lot of sense(!). So I'll try to estimate some numbers, and then maybe we can use your data to refine our theoretical understanding....
Great work, Peter -- do keep it coming!
- W


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## pyce (Nov 7, 2001)

*Why the different curves give different comfort ...*

This one little bit late, but wanted to go over it, so it eventually get little bit clearer…..
I have been thinking for the last few months, how exactly to “link” those curves we see from the dyno, with some easy and simple explanation, so everyone can just look at a curve in the future and know exactly what this curve will give when it comes to ride quality and handling characteristics. Two days ago this idea came out and I want to illustrate it here, so you guys tell me whether it makes sense. Here is the sequence and below is the explanation:








Picture 1 – We have out three compression curves (Force vs. Velocity). The Blue is the digressive curve with the “knee”, common damper for our cars. Then the Red curve, which is sort of straight line, which is what we are calling now “linear” curve, which is common damper on some bikes. Then the Orange curve, which is the so called “progressive” damper, also found on some bikes. 
Especially in the beginning of this thread, we have been puzzled why the “knee” from those digressive curves give the discomfort, and why there are some dampers with higher values of high speed compression, yet they are more comfortable than some other dampers with low values, but with more pronounced “knee”. So, here is this attempt to explain it:
Picture 2 – Let’s extract these three curves from picture 1 and put them in three different scenarios. Let’s involve some sort of a heavy ball that comes from the left at speed and basically use the shapes of those three curves to build a path together with the flat surface where the ball comes from. The goal here is to slow down and stop the ball. The ball has the same weight and comes at the same speed for all three scenarios. The only difference is “the shape” that stopping path has.
So, with some imagination, it is pretty easy to predict what the ball will do on this picture #2. It will “hit” the curve and depending on the speed, it will bounce (more or less) and may even jump over the knee if the speed is too high, then land after the “knee” and then bounce again, slowing down. You can all build this kind of paths at home, with some harder paper and experiment the different angles of impact, but I am sure everyone can figure out these pictures above….
Picture 3 – Same thing, this time we have the “linear” path. The ball comes, hits the path, but as this path is more slanted in its first part (compared to the blue in its first part), the impact will be less harsh and the bounce will be less too. Then the ball has to claim steeper path, so it slows down faster too. Anyway, it is pretty visible why it is a more comfortable way to slow down the ball…
Picture 4 – This one is perhaps the best way to slow down the ball, as virtually there is no impact. The path aligns perfectly with the platform where the ball comes from, so the “claiming” up happens smoothly. This path has to be the steepest thought, with the highest value of high speed, as the ball starts the “claiming” at full speed as it has not been disturbed or slowed down by anything like in the other two scenarios. Basically, there is no initial impact to slow the ball dramatically, so if we want to stop the ball by the end of the path, that path has to be pretty steep.
I hope this makes some sense…..


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## vasillalov (Nov 5, 2003)

*Re: Why the different curves give different comfort ... (pyce)*

Damn you are good!
Makes perfect sense!


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## groftja (Jul 19, 2004)

*Re: Why the different curves give different comfort ... (pyce)*

A really good way to analyze this would be too determine the following variables for the damper/spring/vehicle mass system for different bump scenarios: 
Force (combined spring/damper forces) vs time, 
Vehicle vertical acceleration, velocity, displacement vs time 
Make it simple though by keeping it one-dimensional: one spring/damper and a mass that is 30% of the total vehicle mass (as in 1 front corner). Use the spring/damper/mass equations in physics books.
The vertical force on our butts is what makes us say certain shocks are uncomfortable, so run the equations for different dampers and different bumps. Try sudden low amplitude bumps, gradual high amplitude bumps with each damper curve type. The vehicle's vertical acceleration is what determines the force on our butts so that is why vehicle mass is important to include in the analysis.
There could be some tough issues to decide in this analysis that I have not considered.


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## pyce (Nov 7, 2001)

*Re: The New Base Valves .... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_ …. So you'll bend the washers in 2-D, like a potato chip, instead of in 3-D, like a cone? -- a very clever way of softening the rate! 

Yes, exactly! Very good way of explaining it – potato chip! Fantastic







We are after the smoothest transition of the oil, with the quickest (as well) control, so Phil thinks this is the way to go for our somehow “little” damper. Basically, the whole scenario changed when the oil quantity numbers came out. Phil was thinking to go “four ways” like many bike dampers, but we could not make a hole smaller than 1 mm. with the tools he has, and four holes could not work anything on the high speed. He actually thinks that even those two holes could be “too much” of a diameter, but we have to try it first and see…….

_Quote, originally posted by *Ceilidh* »_ …. Strongly progressive dampers (what you'd achieve with simple orifices without any valving at all) were abandoned long ago on passenger cars, but I've heard tales of mild progressives used on some OEM suspensions …. 

Would be interesting to hear the tales, I am curious!







Anyway, I actually had this idea a week ago, to try to run the damper with no washers, just leave the small holes on the base valve to do the “choke” as to see what that would give me. Basically to do some sort of “basic damper”, very progressive, as you described above. Well, the thing is, these Konis can not be run this way. There is a need of at least one washer, even if it has to be the thinnest thing ever. If you run with no washers at all, the oil at low speeds flows through so easy, there is no enough pressure as to bring some oil above the piston, in the rebound chamber. So, what happens is, the rebound chamber gets empty after few cycles and oy-la-la, there is no more damper, LOL!







Basically, the idea behind this was to see what just the holes do, so to guess the right size and number of holes for the high speed without being confused from the curves that the washers give. Then, combining some soft washers with the right size high speed holes, could have given us actually the FiBoL, but of course, it was not meant to happen. But we will see how these experiments go with the base valve V2.0 and perhaps we will be capable to get that curve Kevin was talking about. I guess it will feel very different from achieving it via 2-stage stack, but if it works, who cares how do you get it…..

_Quote, originally posted by *Ceilidh* »_ …..If I can find some time this weekend, I'll try to work out some rough estimates of wheel/shock velocities in different situations; I used to think that we had to blow off the high-speed compression to be soft on chatter bumps, but last month's calculations of impact speeds on jump-landing (plus Phil's continued insistence that progressive compression is the way to go!) have made me wonder: perhaps the "sharp road bumps" that we'd like to soften actually occur in association with relatively low piston speeds, in which case your/Phil's progressive curves would make a lot of sense(!). So I'll try to estimate some numbers, and then maybe we can use your data to refine our theoretical understanding....

Groftja and you can do a great team for these things. See his post above. I will try to work on some schematics of what actually happens when we hit a bump and try to do a graph (a curve) that shows where exactly the damper’s curve goes through while goes over the bump on the road. We do dyno at specific speeds and analyze the curves at each speed, but when we hit a bump, the piston goes through several “speeds” for its stroke and the curve at that point must be very different than those we are analyzing. Perhaps I am wrong, but I want to dig more into all this.


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## pyce (Nov 7, 2001)

*Another New Base Valve - V3.0*

The last Base Valve 2.0 did not quiet give us what we wanted..... The two holes are too close to the center (they are on imaginary circle with diameter of 9 mm) and then using the bolt head of 7 mm, this makes the oil jets acting way too close to the bending point, so the low speed was not weak at all







It works well otherwise, the curve shapes are there, but the values are too strong, especially at low speeds….
So, new Base Valve is coming and here is how we are going to "move" the holes far from the center while maintaining the original body of the valve:








The orangish part is a separate piece that will go on top of the modified valve. This way we can quickly move the holes around if needed, without filling and re-machining the valve again and again. The only part I do not like is the sort of a "tank" that we have to have between the two parts, so the oil flows from the inner base holes to the outer top holes. Would have been better if the holes go directly from the compression main chamber to the washers, but it is not possible to do so with the existing valve without major modifications, so we will use this V3.0 just to see what the new hole position will give us and if it works, then we can eliminate the "tank" and go one piece everything.


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## pyce (Nov 7, 2001)

*Re: Inside the Rear Koni Red ..... (kevinstillwell)*


_Quote, originally posted by *kevinstillwell* »_ .....I have to wonder how the cupping action of the face shims affects the oil flow as it escapes from between the two shims in questions. 









Kevin, I am only now able to slowly answer your questions one by one. So, let's start here....
What you are talking about must be some very important issue, because the Boge-Sachs OE dampers do address it and perhaps the whole foot valve is designed in a different way (and those fancy washers must be more expansive too!) with the only scoop to address this oil-in-between-the-stages issue. I am doing a complete model of the whole rebound mechanism and only now could see how they have addressed it! Allow me to finish it by tomorrow and I will post some sections and exploded views, so it will be easier to visualize. But my point is - if they have gone to a more complex foot valve (and now rebound valve too!) just for this issue, it perhaps must be a serious issue.


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## John A (Feb 19, 2001)

*Re: Inside the Rear Koni Red ..... (pyce)*

thought you'd get a kick out of this, from tokico:








http://****************.com/smile/emthup.gif


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## pyce (Nov 7, 2001)

*Re: Inside the Rear Koni Red ..... (John A)*

Great, John! We now have a "dyno" from a Tokico...... finally! 
Ok, I did quick check with the data we have so far from our OE dampers. Amazingly enough, the curve the their graph provides for "OE" is incredibly close to the curve we have! The only thing that is not quiet like on their graph is the very sharp knee on the OE rebound. However, the OE rebound on our dyno graphs looks exactly the same, just that sharp knee is much softer, but the main two lines of the rebound (before and after the knee) and the compression line look absolutely spot on! Now, the even more interesting part is that if you convert their units into in/sec for the speed and lb. for the force, the highest values for the compression and rebound they give on their graph come to about 100 lb (compression) and 220 lb (rebound) and that is on a speed of 0,6 m/sec which is about 23.6 in/sec. If you look at our OE graphs (for example the one at 30 in/sec on page 5), those two numbers (100 and 220) are spot on!!! So, they do not specify which damper is their "OE", but beside the sharpens of that knee, their graph is spot on with ours from the rear TDI OEM Boge-Sachs damper, so perhaps this graph is not some smoke and mirrors marketing painting.......
Now, if the Tokico graph is as close to the real as the "OE" is, we can predict that this is going to be some sort of "TC Double-Sport"









The rebound value is so freaking high, it is actually significantly higher than the highest we have seen so far, which is the full stiff on Koni Yellow! We are talking here 500 lb of force at speed of only 23.6 in/sec.







All this, provided that we are looking at a graph that represents the Rear OE and Tokico dampers (and again, I am assuming that as their "OE" curve is incredibly close to our OEM Rear curve!).
If their rears are like shown on that graph, this will be the firmest/harshest damper from all we tested so far! This damper may also start jacking-down pretty badly. It will be a great auto-cross damper thought. For street use, with this rebound, the body will roll together with the wheels, LOL! So, if someone has this damper and the graphs are real - please do never complain about body roll, you should have none!








John, do we know more about which model is this, which setting (if adjustable), etc? Thanks for posting it here. Perhaps one day I will find someone who will let me dyno his Tokico and then we will know more.


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## John A (Feb 19, 2001)

*Re: Inside the Rear Koni Red ..... (pyce)*

I believe it's an HP -- the graph came from this page:
http://www.tokicogasshocks.com....html
No idea on front / rear, or even application -- though it says 'golf' on the graph and they show an A3 golf on the page. 
They also have graphs for their new 'd-spec' adjustables, but there aren't any VW applications yet. 
i'm more shocked than anyone that it was that close to real life!







i'll try to find out tomorrow what specific application it is. http://****************.com/smile/emthup.gif


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## pyce (Nov 7, 2001)

*Inside the OE Boge-Sachc Rebound Valve.....*

Here is the model (part of it, as we do not need to make it more complex for the purpose of this post) of the Rebound Valve and related stack from the OE Boge-Sachs Damper:










Now, let's take a close look at the highlighted area, which is basically the "bottom" of the Stack even if it is on top. (This is Rebound, so when it works it will be inverted, but for simplicity is presented here upside-down):










The section and the red-line flow may not make sense as the shape of the washers is not easy to see from the above section, so here we have those same washers "exploded":









So, the oil flows as indicated with the big red arrow. It goes through the three cuts that the #1 bleed Washer has at the very low speed. When the speed gets higher, the bleed is not enough and it starts pressing on the Washer #2, which is the main (and only, in this case) washer from the so called Stage One. As to have a "staged" stack, we need then a "separator", which in this case is the Washer #3....... Till here is pretty basic. Then later we have to have the other (blue) washers that are basically the Stage Two and so on........ But in between that Separator (#3) and the rest of the Stage Two, there is the Washer #4, which I could not figure out why the hack it is there!? ........ Until Kevin's point above about what happens with the "trapped" oil in between the stages. Now, I may still be wrong here, but at this point, looking at the design of the #4 and where it sits, it makes a lot of sense (at least to me) that such washer is there for only one reason - to prevent that the oil between the stages gets "trapped". If this is correct, then perhaps that is a serious enough issue, so Boge-Sachs had to make the valve more complex, the washers more complex (and expansive!) as to solve it. Perhaps also it has to do something with the fact that the "separator" is extremely thin (0,15 mm) and having those "escape" holes on washer #4 is a must for other purposes that have something to do with oil viscosity, flow, etc..... 
What do you think?


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## catalytic (Jul 31, 2001)

*Re: Inside the OE Boge-Sachc Rebound Valve..... (pyce)*

Wow. This is an amazing thread. I haven't been in the Suspension forum for years and look what greets me upon my return: 12 pages of hard core technical goodness. ... Actually, it's too much! 
I don't know if you recall, but I was fairly serious about this stuff for a couple years as I was researching and reviewing my Eibach ProSystem. My review thread (see link in my sig) generated hundreds of replies and tens of thousands of views. Almost as much as this one. But nowhere near the amount of empirial technical data as this thread... Bravo!
I do have a couple suggestions, though... there are a lot of F-d curves, and a lot of them measured at very high piston velocities (velocities not always representative of real-world measures of handling characteristics... you want to focus on the 3-12 in/s range). If you only want to publish a couple graphs on each shock, I would strongly recommend going with a single cleaned-up common-origin F-V curve instead. You can get almost the full story of a shock's ride and handling characteristics in a single, easy-to-read graph, whereas with the F-d curves, you need F-d measurements at at least 3-4 different piston velocities (say 2, 6, 10 and 18 in/s) to get the story, but then you have to put together your own puzzle by tracking what each shock does at each velocity on compression and rebound and draw the F-V curve in your mind. 
It's all about the shape of the F-V curve... and to a lesser extent, the critical first quarter-inch of piston travel at the beginning of compression and rebound. But given a single choice, F-V all the way. You can infer the initial F-d behaviour by the very slow speed damping.
Please keep in mind that I do appreciate the amazing amount of hard work that you have done and don't want to come in and criticize... just want to offer this suggestion as I feel it will save everyone time -- so you don't have to create as many graphs, and we don't have to read as many or spend as much time interpreting.
As for the Eibach ProDamper... somebody asked the question what would its dyno curve look like? It is actually quite similar to the Koni Sport. It is a progressive shock and is soft on compression at low piston velocities, but quickly builds compression to match other sport shocks at medium-high piston velocities. Rebound is also much like the Koni at full soft. A little firmer than stock at low velocities, but flattens out a bit at higher velocities.
The design philosophy behind the progressive compression curve is likely so that a softer spring can be used to maximize comfort (reduces g-forces and lowers the resonant frequency of the chassis/suspension system) without bottoming out. With a big bump, the shock plays a big role in helping out the spring, effectively adding spring rate at crucial moments, but keeping it smoother where possible. This is also why the ProSystem can be made to bottom on slower speed bumps/potholes (can happen to me coming out of driveways) but it rarely happens at higher speeds with sharper impacts.
It is interesting how the ProDampers can be relatively similar to the Koni Sport, even though the ProDampers are custom made by Sachs-Boge to Eibach's specifications. Maybe Eibach said "we like how the Koni rides and handles... make us something similar"










_Modified by catalytic at 3:47 AM 4-30-2005_


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## catalytic (Jul 31, 2001)

*Re: Inside the OE Boge-Sachc Rebound Valve..... (catalytic)*

I do want to comment on the Bilstein TC. I thought the Tokico HP was bad. We have another contender for the ridiculously high rebound damping award... although from your measurements, it seems that nobody can match the lunacy of Tokico. I'm surprised at Bilstein. The TC was marketed as a touring shock that was supposed to be used as an OE or OE-plus upgrade -- not really for use with lowering springs (and certainly not fairly aggressive ones at that, which the rebound damping would suggest).
It's almost irresponsible to sell shocks like the TC and the Tokico knowing that unless the customer has very aggressive springs (we're talking 300-400 lb/in here), the rebound damping is simply too firm. It is inevitabe that jacking-down of the suspension will occur with OE or even mild sport springs like the Eibach ProKit... perhaps even regular sport springs like H&R and Neuspeed Sport.
There is simply not enough attention paid to matching rebound damping to the spring rate. Too often, adjustable rebound damping is used as a device to tune the ride comfort or handling sportiness or the car (when it should really be used to match the rebound damping to the springs you're running). ... Too often, aftermarket shocks are selected without any regard to the springs that will be used with them. 
pyce, your empirical data gives people a valuable resource that enables them to do just that. For once, one can make an informed spring-shock match... or be able to tune adjustable shocks effectively. And that, my friend, is priceless.











_Modified by catalytic at 3:55 AM 4-30-2005_


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## catalytic (Jul 31, 2001)

*Re: Inside the OE Boge-Sachc Rebound Valve..... (catalytic)*

Seems to me that the Koni Revalved v1.3 has the right level of compression damping at higher piston velocities, but it does look like it is a little soft at low piston velocities. Might need to change the stack to maintain the low piston velocity damping while flattening out the progressivity at higher velocities.


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## tdigearhead (Mar 8, 2004)

*Re: Inside the OE Boge-Sachc Rebound Valve..... (catalytic)*

Are the Koni Specials (Red) available for sale in the US?


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## Ceilidh (Jan 7, 2004)

*Re: Why the different curves give different comfort ... (pyce)*


_Quote, originally posted by *pyce* »_










Hi Everyone








Peter's asked me to comment on his "rolling ball" analogy, and I'll do so anon (hopefully in a matter of days, though this is another busy week). But to set the stage for that, and also because this thread's become long enough to obscure what the basic goals are, we'll first "resynch" on some of the basics.
I. Shock Damping Curves: Types and Definitions
There are four basic shock damping curves (which one can combine in various ways to achieve an infinite variety of compound curves). These are:
A) Constant Force.
This curve is not shown in the above Force-Velocity plot, but would appear as a flat, horizontal line some distance above the X- (velocity) axis. This is a force that resists shock motion by a constant amount, irrespective of how fast the shock is extending or compressing. It is the damping that a 1930's vintage friction shock absorber gives you (though most friction shocks add an additional spike at zero-velocity, because static friction is typically greater than sliding friction), and it provides the less-than-ideal combination of an extremely, harsh noisy ride coupled to extremely poor chassis control.
Modern cars typically do not employ this curve, save in two situations:
1) When your shocks are mechanically blown (not just worn out, but with burst seals, hydraulic fluid leaking everywhere, and heavy scoring/rust on the piston rods), the absolutely awful ride & handling that ensue are because you have shifted to the constant-force/friction shock curve.
2) If you install certain types of aftermarket bushings (a topic of other threads), you will similarly introduce the 1930's ride.
.
B) Linear Damping / Velocity-Proportional Force
Herein is the RED line on the topmost graph, in which the damping force is directly proportional to the shock piston velocity. This curve has the property of minimizing the acceleration felt by the chassis as it bounces on the springs, and it causes the minimal degree of "jerk" (rate of change of acceleration) during chassis bounce.
The Linear Curve is difficult to produce at all but the lowest piston velocities (at low velocities, one can set up a linear curve using a bleed valve at laminar flow); linearity at moderate and high piston speeds requires extremely careful valve design and setup.
Linearity provides the most comfortable ride in the "normal" regime of chassis bounce/oscillation.
.
C) Progressive Damping
The opposite of what many people think it is (because the technical terminology clashes somewhat with normal English usage), this is the ORANGE curve, not the blue, in the topmost graph. This curve markedly increases damping force with velocity, so that rapid piston motions are damped far more strongly than are slow movements.
A strongly progressive curve is extremely easy to produce: any open orifice (without any valve at all) with a rough wall will produce a curve where damping increases with the square of velocity. (With a smooth-wall orifice, the damping is initially linear (laminar flow), then switches to progressive when turbulence sets in.) A weakly progressive curve such as the ORANGE line requires careful valving design.
Strongly progressive damping was a feature of cars in the 1940s (replacing the friction damping of the 1930s), and whilst not as awful as the friction damping in ride and handling, nonetheless was pretty bad. The rolling, heaving, swaying, and bobbing seen in 1940s and 1950s movie car chases show what happens when you don't strongly control the low-velocity chassis movements, and the stiff high-velocity damping can telegraph sharp jolts straight into the cabin.
Weakly progressive damping of the sort Peter is trying out is more of an unknown quantity, and Peter/Phil's intuition is that it might work out well for our cars....
.
D) Digressive Damping
The BLUE curve in the topmost diagram, the Digressive Damping curve rolls off the high velocity damping to reduce the jolting effects of high-speed bumps. Here, the philosophy is one of firmly controlling chassis motions with stiff low-speed damping while blowing off the high-speed impact from sharp bumps.
The Digressive Curve is the basic damping curve employed in most shocks. Despite marketing claims to the contrary, it does not always yield good ride comfort or roadholding, as the stiff low-velocity damping lleads to a nervous, jitter ride, and a poorly-handled low speed/ high speed transition will produce strong "jerking" motions. Thus the comfort & performance of a digressive curve strongly depend on the details of the curve -- not all digressives work well.








II. A Very Bad Curve
Above is the Tokico damping curve kindly posted by John A. Peter's OE measurements suggest the curves might not be exactly shaped as shown, which is a very good thing(!): the RED rebound curve as shown is that of an extremely poorly done shock. The initial steep (low-speed) section is progressive, followed by an extremely sharp kink and an abrupt linear section. The linearity occurs primarily in a velocity regime above that of chassis bounce, so the the linearity does no good for chassis ride (remember, the linear curve yields the most comfortable chassis bounce -- but only if it's linear at the velocities in which the chassis bounces). On the largest bounces and on moderate bumps, the shock will transition across the sharp kink: here, the abrupt change in damping force leads to an abrupt change in acceleration, which will be experienced by passengers as a sudden upwards or downwards jerking motion.
Fortunately for Tokico, the true damping curve is probably (hopefully) much smoother than plotted; because the marketing literature from a number of shock manufacturers have conditioned people to equate strongly digressive = good handling + comfortable ride, presumably Tokico has doctored this graph to make the digressive elements glaringly apparent.
.
III. What Peter & Phil Are Trying Out
Alas, this section will have to wait for a later installment -- in basic terms, Peter is trying out a Linear Shock (max comfort in chassis bounce) with a mildly progressive low-velocity "nose" (to reduce chassis nervousness on small road undulations and road camber changes), and he'll be playing with a smooth digressive roll off on high-speed bumps, and/or perhaps a final progressive round-up to accommodate high speed jump landings/ bottoming. In more general terms, he and Phil are exploring whether the basic aftermarket Digressive Curve (which gives a racy "feel" at the expense of a frequently poor ride) can be tweaked to produce something both faster and more comfortable.
More later, when I get unswamped with work!
- C


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## alexb75 (Dec 29, 2002)

*Re: Inside the OE Boge-Sachc Rebound Valve..... (tdigearhead)*

Hi everyone...
Jeez, amazing work guys... incredible!!!
Sorry I have been away from the forums... life's taking over, finishing school, looking for a job, new GF







etc...
At the same time, I am quite tired of trying to re-invent the wheel on our cars. Too much energy, time and money spent already. These discussions are GREAT for education but at the end of the day it has been done by engineers at major car manufacturers. 
VW MK4 was never built to handle a race track and has a base suspension that is designed to RIDE well while handling better than most stock cars. Not sure why we all got this idea that this car has to handle like a Porsche! It was never meant to do that... 
The other issue was that I never got to try a good handling MK4 that was riding fine... the design doesn't allow that... for handling properly you NEED to stiffen the rear and as soon as you do that, you lose ride quality dramatically. So, it's very hard to do a suspension upgrade that does ok around a track and still rides fine around the streets. The obvious solution was an adjustable suspension that can be softened for street, but the fact that in almost all adjustable shocks, the rears have to come off the car, then it's almost just as un-adjustable. The idea of adding rings to the rear (by Peter) is great alternative...
So, for me, after all the trial and errors, 4 different suspensions and trying almost ALL combinations of Koni settings on my car, I have decided that the best way to achieve what I'm looking for is to get into another car! For people who don't know, I race occasionally while I value ride comfort.
In my search, I have tried a few cars and I am quite amazed by the new Audi A3, as well as the MK5. They both handle very well while ride is great too. A3 specially had the best balance of firm ride and great handling. I tried the same corner with my car (Koni/sticky tires) and then stock A3 with all-season tires... I was only 5Km/h slower on A3 and that was my first time trying out the car with the salesperson sitting next to me... So, I am pretty sure I can take that corner faster if I get to know the car better and if I choose a better line.
So, not to spoil anything here... but some other cars are designed differently that meets the need of handling enthusiasts without all the aftermarket suspension trial and error... 
I am still following the thread to learn more, but I am really tired of changing stuff on my car to achieve what I want, while it is already engineered out there...


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## Ceilidh (Jan 7, 2004)

*Re: Inside the OE Boge-Sachc Rebound Valve..... (alexb75)*


_Quote, originally posted by *alexb75* »_......
VW MK4 was never built to handle a race track and has a base suspension that is designed to RIDE well while handling better than most stock cars. Not sure why we all got this idea that this car has to handle like a Porsche! It was never meant to do that... ........I have decided that the best way to achieve what I'm looking for is to get into another car! .......
In my search, I have tried a few cars and I am quite amazed by the new Audi A3, as well as the MK5. They both handle very well while ride is great too....

Hello Alex!
Welcome back!
I've got my eye on the 4-door MINI that was spotted testing last month; it's supposedly an '07, which would time out very well for me!
-C
P.S. -- Don't worry Peter, I'll stick with my GTI for at least another 2-3 years, so the suspension collaboration will continue!


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## alexb75 (Dec 29, 2002)

*Re: Inside the OE Boge-Sachc Rebound Valve..... (Ceilidh)*


_Quote, originally posted by *Ceilidh* »_
Hello Alex!
Welcome back!
I've got my eye on the 4-door MINI that was spotted testing last month; it's supposedly an '07, which would time out very well for me!
-C
P.S. -- Don't worry Peter, I'll stick with my GTI for at least another 2-3 years, so the suspension collaboration will continue!









We all need to support Peter there! Eventhough he told me he might get into a Passat soon


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## placenta (Jun 3, 2003)

no updates in a while!!


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## pyce (Nov 7, 2001)

*Updates....*

No updates because if I start writing about what we do almost every day, this thread will go to 30 pages and as mentioned above, it is already too long. I will write a more detailed description to what was done and how was done when we have some results. In few words, here is what is going on:
1. We have managed to achieve the three different curves, described very well by Winston in the post above. 
2. I got tired to put in and pull out the dampers every time as to try the “curves” on the car.
3. Because of #2, we are finalizing a model of a home-made damper that could be incorporated in the existing Koni Yellow body. The damper then will become a 4-way adjustable, both front and rear, and all of that will be external, so quick adjustments could be done on the spot. This is the only way we can reproduce almost any curve from the dyno to the street in few seconds, so then we will have the final database of what settings work on what springs, what roads, speeds, etc. 
4. Final goal is to use this fully adjustable damper to work with a set of Shine springs (Dick kindly sent me a set last week!) and have, finally, the sweet spot between decent handling and decent comfort. The optimal settings (curves) could be then duplicated on ordinary Bilsteins or Konis or anything else that offers the possibility to be revalved.
That’s pretty much it.


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## catalytic (Jul 31, 2001)

*Re: Updates.... (pyce)*

4 way adjustable? Can you elaborate? You mean compression and rebound and progressivity/digressivity as well?


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## John A (Feb 19, 2001)

*Re: Updates.... (pyce)*

peter,
just to keep everyone on their toes, here's a decent internal view of a penske 8100 series adjustable.








just as a view of how other parts are getting the job done.
http://****************.com/smile/emthup.gif


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## John A (Feb 19, 2001)

*Re: Updates.... (catalytic)*


_Quote, originally posted by *catalytic* »_4 way adjustable? Can you elaborate? You mean compression and rebound and progressivity/digressivity as well? 

i'm guessing compression: high speed / low speed, and rebound: high speed / low speed.


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## pyce (Nov 7, 2001)

*Re: Updates.... (John A)*


_Quote, originally posted by *John A* »_
i'm guessing compression: high speed / low speed, and rebound: high speed / low speed.


Yes, that is what it would be. Initially we are going to use the Yellows, so to take advantage of the rebound external existing adjuster (front) and will concentrate on the compression only. The range the Koni Yellow gives is just enough for these experiments, it does not matter much (for now) that it does not give separate low/high speed adjustments. So, the first piece is going to be sort of 3+1 way adjustable. 3 is rebound, low speed compression, high speed compression and "plus 1" is because there will be a bleed adjuster as well. The idea is that the damper could be set to work from full leak with no force at all, to a complete hydro lock where there is no movement at all







It will be a small machined piece that goes through the very bottom of the front damper, basically the place Koni uses to make their Yellows externally adjustable in compression. Three knobs in there, so it could be reached with fingers. The place is not ideal for quick adjustments, but still better than taking out the whole damper. For the rears, there will be a piece sticking out just above the bottom bushing, facing the rear, so one can reach from behind the rear wheel and adjust. I will post the models later, and if anyone is interested, I can send you the CAD data, so you can machine it for yourself. Trying to build the piece in a way that only commercially available parts are used (like the springs, O-rings, balls, etc) so everyone can but them from where I get them and be able to duplicate the results. The very final goal in all this exercise is to fabricate parts that could transform the existing OE dampers into 4-way externally adjustable pieces, so people can use their existing dampers (cheap!) and have some fun with them.


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## John A (Feb 19, 2001)

*Re: Updates.... (pyce)*

4-way adjustable OEM's! you're insane, and i dig it!
i need to pay you to help me develop my racecar shocks.


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## Dae_bro. (Jul 27, 2004)

*Re: Dampers (Shocks) .... little bit more about them (pyce)*


_Quote, originally posted by *pyce* »_Re: Dampers (Shocks) .... little bit more about them (pyce)

a little? gawd, "i think ive gone, crosseyed" 
great resource, but to me its greek.
im just a little overwhelmed, thats all. http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif


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## catalytic (Jul 31, 2001)

*Re: Updates.... (pyce)*

Oh no... I have been such a good boy, staying away from every tempting mod to add to my car for the past 2 years. But 4 way externally adjustable shocks? Evil. You're the devil in disguise!


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## John A (Feb 19, 2001)

*Re: Updates.... (catalytic)*


_Quote, originally posted by *catalytic* »_Oh no... I have been such a good boy, staying away from every tempting mod to add to my car for the past 2 years. But 4 way externally adjustable shocks? Evil. You're the devil in disguise!

which is funny, because i'd totally run 4 way adjustable shocks -- and then i'd adjust them furiously until i liked how they drove, and then i'd stop. 
i SPECIFICALLY built my autox car without adjustable shocks -- i wanted this car to be about learning to drive, so if the car won't do something, i need to change my driving or change tire pressures -- i see sooo many people spend the time between runs messing with konis / penskes / etc.... me, i check tire pressures and visualize the next run. 
i'm very curious to see how they're adding external adjustment, though i've been reading some stuff about how other companies do it, so i'm getting ideas...


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## Girlsound (Apr 27, 2002)

*Re: Updates.... (catalytic)*


_Quote, originally posted by *catalytic* »_Oh no... I have been such a good boy, staying away from every tempting mod to add to my car for the past 2 years. But 4 way externally adjustable shocks? _Evil. You're the devil in disguise!_

I agree...and I'll gladly sell my soul.


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## pyce (Nov 7, 2001)

*The 3-Way ....*

I would completely agree that adjustability could be something so wrong, as it will distract too much, the user will keep going all day long and at the end may turn counterproductive! The whole reason we decide to do it is because with the current way we conduct the experiments, it takes a lot of time and we will never explore certain “curves” as taking out the dampers all the time is simply discouraging. Plus, I am very interested to make some sort of database for how damper curves work with different spring rates. Basically, there is this popular term here, “matched shocks and springs” and my desire is to explore this matching and try to establish a pattern between damper curves and spring rates, mainly for comfort and then for improved traction (grip). The only way this could happen fast and efficiently, is if we use some sort of externally adjustable damper which will allows us to adjust more that one parameter. So, the idea of this damper came out. Otherwise, we have to take the front damper let’s say 100 times as to get to some serious conclusions and you all understand that the task is almost impossible, at least for me. Plus, by the time I get to the “version 50” I will forget what was the feel of “version 5”. With this new damper, we can do all 100 in one dedicated Sunday, on various road surfaces, etc. 
Anyway, here is the basic concept of the compression adjustment for the front damper. This is only the general idea as the actual model has a lot more cuts and parts, etc so it looks more difficult to comprehend. This picture here is missing the whole “reverse flow” system, the one that allows the oil to go back into the tube during rebound, etc. Just take it as conceptual model:








With the lower two knob we can adjust separately the low speed (which is the spring load) and the high speed (which is the max amount the ball can move). Then we have on the left the green “needle” that controls the bypass oil, which is essentially our bleed. Again, this is just the principle. However, the actual dimensions and the position of the controls will not change much. Before someone makes the comment that it is hard to adjust down there, I would like to say that this is still better than taking out the damper. The whole thing could be done in a much more elegant way, but then we need to start changing the damper’s body and I absolutely do not want to do so, as I have no idea how much the strength is going to be affected, etc. That is pretty much it for now.


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## ewongkaizen (Apr 19, 2002)

*Re: The 3-Way .... (pyce)*

and then there are BYPASS shocks.... POSITION sensitive as well....
(i.e. the compression rate can INCREASE at closer to bottoming....)


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## supersonico (Aug 10, 2003)

I have a question, and don´t know if it belongs here, but I´ll ask anyway. (I am known as a thread hijacker in my home country´s forums, anyway).
Is strut noise a reliable way of telling whether it´s worn out? I have no other MkIV´s I can drive nearby to check whether mine are rolling their little eyes up and calling for MAMA while praying for forgiveness, but I have been noticing increased PFFFFSSSHHHs by my front wheels whenever I hit bumps. My car´s going on 40K miles (it´s now at 63K km), but I´ve done about 70-80 percent highway driving in it, and it appreciates the circumstance, for my dad´s Vectra was having its second suspension major overhaul by that mileage (100% city driving on a 3rd world city, which equals your good old Dakar rally with all the bumps and dips and whatever).
Both fronts and rears are by MONROE, by the way, and belong to what ETKA says to be the "heavy duty" 4-door Golf suspension. The rears, believe it or not, are quite, um, quiet.


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## JasonC SBB (Jun 3, 2005)

*Re: Dampers (Shocks) .... little bit more about them (pyce)*

<jumping in very late>
Did anyone do an FFT on the accelerometer data? If not, send me the raw data, I'll do it.


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## IndigoBlueWagon (Aug 9, 2004)

*Re: Dampers (JasonC SBB)*

I just wanted to post that Koni Reds are now installed in my Wagon, replacing the Bilstein HDs. I have the original OE springs and a Shine rear bar in the car. 
All I can say is WHAT A DIFFERENCE! I think saying these dampers have an OE-like ride sells them short; it is incredibly smooth, but in so many ways better than OE! Much more controlled, better turn-in, but still very smooth. I didn't realize how much I was aware of the expansion joints and bumps on my commute with the HDs, but now that the Reds are in it's like the bumps are gone. 
I put the Reds on full soft as Peter recommended, even though I was concerned that they'd be too soft. I shouldn't have worried. 
Now that I've gone from stock to Shine and back to reds and a rear bar, I think this is the best setup for me. I don't drive very hard but I like a car that corners well, and this now fits the bill. 
Thanks, guys for all your work on this thread. Without this info I probably wouldn't have tried the Konis. Your thoughtful work made the difference. Thanks.


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## Occams_Razor (Jun 28, 2003)

*Re: Dampers (IndigoBlueWagon)*

Bump!


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## pyce (Nov 7, 2001)

*Updates....*

I guess the “bump” is for some updates, and if that is the case, here is what we are doing these days:
(I am trying to keep it off-line and will eventually put everything together once it is all done, so we do not make the thread 20 pages as it is already too long and no one reads it)
1. I have been riding the liner dampers (Koni V4.X) for quiet some time and they do respond very well on increasing spring rates.
2. The above mentioned spring rates increase is a small experiment we are doing with the stock springs, eliminating coils (or portion of coils) as to get variable (increasing) spring rate, trying to maintain the same ride height. So far I have been to up to 20% spring rate increase and the car is still very comfortable. Meanwhile bottoming had been noticeably reduced.
3. To split the above experiment in parts, we did first the fronts, then the rears, then both at the same time (and variety of combinations in between, using rubber spacers and metal spacers and combinations of both). The car with 20% spring increment all around feels the best from all combinations (so far). On a spring tester we are replicating the experiment as to find out how much we gain by using each spacer, etc.
4. Next steps are to make a device (I am working on it as we speak) that will allow a pretty quick and accurate coil eliminations, so the spring rate could be increased at will in less than 2-3 minutes. I would like to explore the best frequencies front-to-rear and see if the formulas that talk about springs rates are accurate, etc. (It is basically a modified metal clamp that is inverted, so it spreads the coils instead of compressing them).
5. At the same time, we have finally put together the “progressive” damper. It goes with name V5.0. It is a valving that makes the damper work as the linear one, but as the speed gets higher (the shaft speed that is) it ramps up the values, so we have a very comfortable ride, yet pretty strong damper that prevents bottoming on the sharp and deep bangs. This damper provides the very extreme comfort and made me believe that we can use much higher spring rates with great success, even on bad roads, as long as the damping is very carefully put together.
6. Next step is to get coilovers, so standard spring diameters could be used, and start with what they come from the factory (about 400F and 300R) and go up (or down) and see how the valving needs to change for every 50 lb added spring rate. 
7. Went with the H&R DB, this way to perhaps conduct some more scientific tests and finally put behind this whole lowering vs. handling contest. So, there will be some sort of tests with front ride heights, I am just working on the logistics, so we do something more objective, this way there will be no objections after that and we can finally close that chapter and move to something more productive. (I am fully aware that to some folks all the data in the world is not going to make a difference, but these tests are not aiming at them anyway).
8. Needless to say that the H&R DB dampers are going on the dyno as well, so we will see how exactly have the “matched” them, so perhaps we will know more about all this.
That is pretty much (in a very short form) what we have been doing and what is the plan.
P.S: JasonC - you have no e-mail listed in your profile and I tried to contact you via the administrators, but it is not possible, so I have no idea how to send you the data you want....


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## IndigoBlueWagon (Aug 9, 2004)

*Re: Updates.... (pyce)*

I don't think the lowering versus handling debate will ever die. And bear in mind that Dick Shine believes that rear ride height is an important component of handling stability on these cars. So it's not as easy as adjusting the front--both ends matter.


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## Ceilidh (Jan 7, 2004)

*Re: Updates.... (pyce)*


_Quote, originally posted by *pyce* »_....here is what we are doing these days:
1. I have been riding the liner dampers (Koni V4.X) for quiet some time and they do respond very well on increasing spring rates.
2. The above mentioned spring rates increase is a small experiment we are doing with the stock springs, eliminating coils (or portion of coils) as to get variable (increasing) spring rate, trying to maintain the same ride height. So far I have been to up to 20% spring rate increase and the car is still very comfortable. Meanwhile bottoming had been noticeably reduced.
.........


Just to set some of Peter's experiments in context:
1) Most of the experiments are (as one would expect) to explore and quantify the effects that differing ride heights, spring rates, and damper profiles have on real world handling & performance, with the goal of maximizing street performance while maintaining comfort...
2) But some of the experiments (in particular the ones alluded to above) are a little different: they're to investigate how a car can be made more "characterful" while remaining comfortable in normal street use, irrespective of outright performance.
The backdrop to the above is that Peter finally (via his shock/damper tuning) came up with a car that was supremely comfortable and very fast (as measured on the stopwatch) over his long daily commutes on horrible Bay Area concrete freeways -- but then his commute changed, and he found himself bored to tears on a much shorter daily drive.








From his damper experience, Peter's found that the damper profile has an inordinate effect on ride & handling character: with a "Germanic" strongly-digressive shock (one that's very stiff at low piston velocities, but which blows off pressure at high velocities), the ride is very stiff-legged and uncomfortable on bad roads, but the chassis is very responsive to the steering wheel and the handling feels "sporty"; conversely, with a more linear profile (damping forces rise continuously with piston velocity), the handling is much softer, but the ride is much, much more comfortable.
Given the above, Peter's looking at two issues:
A) He's checking the feel of stiffened springs + linear shocks (the idea there is that perhaps the stiff springs can contribute better handling, while the linear shocks keep ride comfort within reason). This approach is actually a fairly classical one (it's the way we used to tune sports cars in the '60s), and if successful it might produce a car that's not particularly fast when measured against the stopwatch (though it should still be much faster than OEM stock), but which will be very "fun" in the way it responds to driver inputs.
B) The other thing he's checking (and this is probably more of interest to most of you) is how handling in general varies if we systematically alter the damping curve from progressive to linear to digressive.
Anyway, Peter's working on several more things too (amazing how much he can get done in his spare time!), but the above is of interest to damping aficionadoes.









Cheers!
- Ceilidh


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## groftja (Jul 19, 2004)

*Re: Updates.... (Ceilidh)*

This is exciting sounding stuff. So the damping you guys are aiming for compared to the digressive damping of "Germanic" damper will be less damping at low speeds and higher higher damping at high speeds? If so, it seems like this will improve comfort (relative to digressive) at low speed driving/less abrupt bumps but maybe be less comfortable during high speed driving/abrupt bumps. I also wonder if you guys have figured out the damper speeds that occur in typical cornering manuevers, since this speed is critical for controlling body roll.


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## pyce (Nov 7, 2001)

*Digressive to Progressive ...*

Here are some of the results mentioned above…
In the first picture we have the Force vs. Velocity graph (at 18.00 in/sec) that shows the linear-initially-to-progressive-later curve. 








The next image is the same curve, but shown in Force vs. Displacement mode and against the rest of the dampers we had. Note, this is a “zoom-in” for the upper left corner, which is basically only the first half of the compression stroke! You can see clearly the difference when compared to the rest of the dampers.








Now, the V5.0 (the progressive damper) is basically a total opposite to almost everything one would experience with the popular dampers (the modern digressive dampers). The car rides like an absolute Camry on 14” wheels! There is almost no feel to what is going on below the rear seat. It is little bit like a train, you hear the track, but you feel nothing much. So, what happens here is, I think we hit the other end of the spectrum with this damper – total comfort, yet very controlled ride, but boring to death, especially on good roads. If we were to get dampers like this on all four corners, I suspect the driver may fall asleep…. And keep in mind, this is with about 20% stiffer springs all around. I have no idea what is going to be if the pure OE springs were used.
Anyway, now we finally got the three curves we wanted to, and we tried them on the car as well (Well, just on the rears, but it gives a very good idea of what the feeling is like). The graph below was one of the main goals in the beginning of this thread, to get all three curves and compare them. I think managed to complete at least this task…








Now, the task is to tweak the valving in a way that going to one end of the adjusting mechanism, we get the progressive curve, for extreme comfort for long trips, etc (folks with stiff springs and 18” wheels will simply love this setting!)…. And going to the other end of the adjustors we get the Bilstein digressive curve for when we feel the need for speed, or just want to dart around on a sunny Sunday morning and feel the road beneath us, having greater steering responses, etc. So, next step is to set the parameters for the adjusting mechanism, so we can navigate between the above described curves.
And by the way, the following is an experiment everyone should do at home! Take out the rear left damper (completely out) and go for a drive. While driving, concentrate on what happens on that particular wheel, trying to ignore the other three. Go first at low speeds over bumps and feel how you actually do not feel much. The even better way (and safer!) to go over those mini-curbs on the drive ways, but under angle, so you can hit the spot with the damper-less wheel alone and compare that feeling to the usual feel you get when you driver over there. It is an outstanding way to understand how much the damper affects the spring’s compression – it is A LOT! Once you do this, you will get new appreciation even for the OE damper and will realize how “stiff” it actually is! After this experiment, it is pretty clear that comfort could be achieved with even much stiffer spring, if only the damper is carefully valved to work with the spring, not against it.
*Important Note:* If you try the above, do take it easy first, increase speed slowly, do not go crazy over huge bumps at very high speed. The reason is, I have no idea what springs you all have, so if it is a short spring that comes out under full extension, then be careful, you do not want this to happen! With the stock springs is ok….. Also, one damper is absolutely enough o keep both sides from bouncing up and down, but if you want to try taking off both dampers – it is totally different story! It is 20 times worse, basically it can’t be driven too fast (if you do not get sea-sick before even leaving the parking lot).


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## groftja (Jul 19, 2004)

*Re: Digressive to Progressive ... (pyce)*

Very nice! To clarify, the 3rd graph shows what you achieved on the V5.0 damper by adjusting its settings...you can have either digressive, linear, or slightly progressive? If so, that is awesome. And will you or someone be selling these dampers or the valving to put in Koni yellows?


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## corrado94 (Sep 22, 2003)

*Re: Digressive to Progressive ... (pyce)*

Great work guys http://****************.com/smile/emthup.gif This will deff work well on the rear of the mkiv for better comfort which is where most of the discomfort comes from and still be able to get the high speed performance . My HR coilover kits ( with high spring rates ) performance is awsome , espec at high speeds , but the comfort at low speeds and espec in the rear is bad. This maybe a way to tweak it a bit .







Bob.G


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## pyce (Nov 7, 2001)

*Re: Digressive to Progressive ... (corrado94)*

No, these curves were obtained with modifying (step by step) the base valve of the Koni Yellow (and the stack on top of it). Not utilizing the remote unit valve. Along the way we realized something important – the remote unit allows too “wide” range of adjustments and that may not be the best idea when it goes to the end user. It may happen that someone turns all the given knobs in ways that throw him/her all the way out of any useable range and that is going to bring lots of trouble. With these simple experiments, we are basically narrowing down the range that will be provided, before the remote unit is cut, so in a way the user can not screw up even with the greatest wish. Basically it may come down to two knobs, one that converts the curve from extreme digressive (for feel) to very progressive (for comfort) and the other knob will give just high speed, basically it will amplify the chosen curve, but without changing its shape. 
Bob, you may be interested in the next few steps of our tweaking, as I also got an H&R coilover kit and planning seriously to make it work well (read: comfortable) on the effed concrete here. I will try to dyno those H&R dampers tonight and see what they give. Anyway, it seems one mo-fo freaking strong damper.


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## corrado94 (Sep 22, 2003)

*Re: Digressive to Progressive ... (pyce)*


_Quote, originally posted by *pyce* »_. 
Bob, you may be interested in the next few steps of our tweaking, as I also got an H&R coilover kit and planning seriously to make it work well (read: comfortable) on the effed concrete here. I will try to dyno those H&R dampers tonight and see what they give. Anyway, it seems one mo-fo freaking strong damper.

 Cool Peter im all ear,s







, That dampner is crazy strong ( atleast the one i have from the RSS club sport kit ) The harder you drive the car the better it handles . I know Mike Potter had this dampner with a 800 lb spring on his front of a mkiv vr6 and he felt it still could have handled even more spring . He tested .95 on the skid pad i believe with this setup







Bob.G


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## pyce (Nov 7, 2001)

*Putting the things together - Part I*

….. 12 pages of theories and dyno curves is kind of enough, isn’t it? So, time to apply some of those theories and see whether we are wrong or right, whether we have learnt something for the last year!







Hang in tight and read this post. It is going to be pretty long, but it is a giant leap ahead and will bring a lot of food for thoughts……
As mentioned in one of the previous posts, one of the main goals with all this revalving was to get a stiff spring to work on the crappy roads, have good comfort level, yet to reduce dramatically body roll in an attempt to keep that geometry in a better shape and therefore to have overall a better handling feel and better road holding. For those who do not have the patience to read the entire post, let me say in a word: We succeeded! The following are just the details about it. (I will put numbers in front, so it will be easier to refer later to specific points for conversation):
1. For years we hear people saying that coilovers (the good ones!) are the way to go, because they were designed to work together (the spring with the damper) and therefore the word “matched” was used more than often. As I had to get some sort of stiff springs for our final experiments, and at the same time wanted to stay at stock ride height – decided to get a set of H&R Dune Buggy coilover kit, as beside fulfilling the request, it is also pretty well known in the community as “one of the best” when it comes to handling vs. comfort. It had been tested before and it was declared that the ride is great, handling too! It is known to have 400 lb/in front springs and about 295 lb/in rear springs, which w will find out later whether is true. So, in an attempt to better understand how all the different components from this system work, decided to install the rear H&R dampers first, in an otherwise stock sprung car, with Koni Yellow revalved to Red spex front dampers. Drove it for few days and must say that the H&R rear damper could actually be almost everything that a mild car enthusiast wants for a daily driven car! It was the best mono-tube damper I ever had on my rear. If you have smooth roads (with no freeway hop and no concrete crap!), these dampers are really a great step ahead of the off-the-shelf Bilstein Sport and HD! The thing is, where are you going to get them from? I have read before they are manufactured by Bilstein, but it is proprietary design by H&R. Fact is, the damper is yellow, but the outside similarity to a Bilstein Sport or HD ends right there. The H&R damper is bigger in diameter as a whole, has bigger shaft (13 mm vs. 12mm Koni and 11 mm Bilsteins and OEM Sachs) and the bottom and top are designed and assembled in a different way. Later on will post a picture, if anyone cares to see what it looks like….
2. Few days later installed the rear H&R springs and set the car at about stock ride height in the rear. Remember, we are still with stock front and Koni. It was very interesting to note that the comfort did not get worse by much (moving from about 120 lb/in spring to about 300 lb/in spring!), so it was already a major step ahead in realizing that indeed we may have success with making this spring work with comfort in mind later on with a different damper. Needless to say that the car is very interesting to drive with front 150 lb/in spring and 300 lb/in rear spring







Understeer is significantly reduced and the inner front tire has some newfound wonderful grip on corner exists that I never had before, but all this was expected and it is not really the point of this experiment. The important parts was the comfort with 300 pound spring could be had with a different damper!
3. Needless to say, the dampers went on the dyno, so to see what is all this matching everybody is talking about, and how exactly they did the valving as to get this damper ride better than your ordinary Bilstein. Well, few pages ago we started experimenting with Linear damping curves and if you all remember, the results were really excellent, to the point that the car got boring to drive on the stock springs. So, I have been wondering since then – Why none of the common dampers does not come with Linear damping, as it gives such great results? Guess what – there are actually manufacturers that do the Linear damping, but you have to unleash the big bucks to get one of those! So, when it comes to make a kit to actually work properly, they do know what to do – Linear damping curves, that is a beauty to watch







Here are two graphs from the H&R DB Rear Damper (Force vs Velocity and Force vs. Displacement):
















Look at the linear rebound curve! These are ALL speeds plotted on top of each other and all you see is one straight line. The compression has slight digression when it goes towards the high speed, but it is still the most linear damper we have ever dynoed (from the purchased in a box dampers)…
Here we have the Force vs. Displacement in several speeds, from 4 to 6 to 18 in/sec in comparison to our old friend, the Bilstein Sport and HD:

























Note how the compression in the H&R is much stronger, yet the rebound is quiet weak (but very smooth!) on low speeds. You would think that a strong spring needs a lot more rebound than what the cheap dampers offer, but looks like it is not the case. At low speeds (2 to 6 in/sec) and even at higher speeds up to 14-16 in/sec, the H&R damper is consistently “below” the values that Sport and HD offer (in rebound), yet, the 300 lb rear spring is not under dampened at all! Only at very high speeds (due to its linearity) the H&R damper shows more and more rebound in comparison to the other two. This is going into a much deeper discussion later in the week, as those values and curves become part of the secrets of how to make a stiff spring ride in comfort and control it as well. The important part here is that the H&R Coilover Kit does come with dampers that are more carefully valved to achieve better results with the stiffer springs that it offers. I just hope that other expansive kits do offer the same or similar work….
Later today will come the rest …..


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## pyce (Nov 7, 2001)

*Putting the things together - Part II*

Continue from above ….
5. Now here is the fun part! Making a valving for the Koni that will make this 300 lb/in rear spring ride nice! It is hard to believe that a strong spring cane be made to ride nice, because the perception had been forever that springs to contribute a lot to the ride harshness in a car, but comes out it is not quiet the case. Yes, a stiffer spring will always ride harder than a softer one, but the difference is not any near as much as one would think. As posted few posts ago, everyone can try on an A4 to disconnect one of the rear dampers and go for a spin, concentrating on what that damper-less wheel is doing. The whole feel that there is actually a wheel and tire and contact with the surface disappears. I tried it with the stock 120 lb/in spring and then with the 300 lb/in H&R spring and the difference is not big – the feeling is that you are actually on 3 wheels, as the fourth one follows the surface without transferring anything to the chassis. So we put the Koni V5.0, which is the progressive damper we talked about just before on this page, the one that has very low and quite linear initially and then slowly becomes progressive compression curve. Looking at where the rebound from the H&R Damper is, it also came pretty clear that you do not need mega-rebound to control that spring, so from comparing the graphs it comes that the Koni rebound should take care of the 300 lb. spring at about 20% to 25% from full soft. We set it at half turn, which should be about there and the dampers went in….
6. The results is, as no one is going to believe it, OE ride quality! Bingo! Yes, it sounds nuts, but hey, I am in the Bay Area and everyone is free to come for a ride. There is little pitch at very high speeds on some surfaces, but that should be result of the twice as stiff rear-to-front spring rates, and anyway it is on speeds that the car is not normally driven. Things will settle once stronger springs go in the front too. I also feel that the rebound we put (25%) is little bit on the low side for fun drive, so perhaps will bring it up to about 30-35% this weekend and see what happens. But those are small details that are of no worries. The important part is that this rear is actually very smooth on the concrete, which is where I usually got the issues with other suspension setups. The only real issue so far is that the car rides like a real Cadillac; there is almost no feel for what is going on the surface below the tires and I am absolutely sure many will dislike it because of that. Basically, I think we hit the sweet spot for absolute comfort (can’t really imagine a 300 lb spring to be comfier than this!) and now have to start backing it off and start trading some comfort for feel, so the car actually feels sporty instead of lust flying into the corners in a boring and character-less way. The road holding is outstanding, but the lack of feel makes you think: “this can not be true!”. Just try to picture a bone-stock Jetta that stays flatter in corners and has significantly less under steer – that’s the car now….
*Bottoming*
7. This one is kind of not directly related to the valving stories, but it is part of the experiments and as the results are worse that what you all would think, I have to share it. It is (again) about the bottoming and the lack of suspension travel our cars have. The tests were conducted with the 300 rear spring, set at stock ride height and with the H&R Damper, which absolutely does not lack compression force! So, we have a pretty serious combo for street use, that should not bottom at all…… I would wish! Check this out: With such a tall and stiff combo, the rear suspension still needs between 1 to 1,5 inches of compression and this is ONLY highway travel we are talking about! No results from rolling in the curves was taken into this. This is basically set the measuring device on the rear right damper, take a right on-ramp (so, no right roll because of the ramp), drive 5 miles straight with no lane change, then take another off-ramp to the right (again, no roll on the right wheel because of the slight curve), stop and check – bam! So, the point I am trying to bring is that unless you have maybe 500-600 lb rear springs, set at stock ride height, no one has even a slight chance of not bottoming their suspension, even when driving on the freeway in a straight line! Later on I will try to measure how much travel we need in a curve, when the car rolls on its side, but I do expect some very big numbers……. Bottom line is, we all bottom, (even if not everyone notices it) unless again, someone has some very stiff springs and set them at stock ride height, which is what I am thinking of trying next, to go up with spring rate and adjust the valving as we go, so to see if it is even possible to get the car not to bottom, while maintaining some decent ride quality. But first we are planning on trying some strong “high speed” valving, as to see how much this can help us in getting there with the existing springs. Some even more interesting weeks are coming…..


----------



## tdigearhead (Mar 8, 2004)

*Re: Putting the things together - Part II (pyce)*

Regarding the stock bump stops, is that why they are so long, especially in the non-sports suspensioned cars so as to become part of the suspension travel? Possibly their length contributes to the feel, or lack of, when the suspension bottoms?


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## groftja (Jul 19, 2004)

*Re: Putting the things together - Part II (pyce)*

Great work! I wonder if the Dunebuggy REAR springs/dampers in combination with the much less stiff FRONT springs/dampers that you had on above offers more performance than you'll get when you put in the Dunebuggy front springs/dampers. It might just add understeer and slightly decrease comfort. I'm excited to find out what you find. http://****************.com/smile/emthup.gif


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## nscirocco (Oct 4, 2000)

*Re: Putting the things together - Part II (groftja)*

how do these compare?
bilstein PSS9









KW V3


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## pyce (Nov 7, 2001)

*Re: Putting the things together - Part II (nscirocco)*

O-ho! These are beautiful! No wonder people are so happy with KW V3. Now it all comes together. On theory website they say that the compression adjustment does change only the low speed, as they have decided not to give the user the freedom to screw-up the high speed..... It is pretty clear from the graphs how the high speed in compression does not change and all the user can do it go from progressive to digressive (through linear) low speed compression, which is really what is all needed for feel. Basically, they do not allow you to play with the parameters that would determine some important suspension behavior, but do let you safely play with the "feel", so you actually notice that things change, and most of all, you can actually really set the car for different scenarios within the given range. The rebound, on the other hand, lets you modify the low and high speed at the same time, and again you have from mild progressive to digressive character, but it is all linked in a way that if you want let's say linear behavior, then you have to crank it to certain levels of high speed, so perhaps it will be easier to screw up with the rebound. I mean, if you tune to reach specific behavior in rebound, you have to live with the given shape of the curve that it is offered at those levels. It looks like the system to have! Too bad they do not offer stock ride height....
As for the PSS9 - that graphs smells little bit of marketing







The lines look like drawn by a child using the windows bitmap package. What strikes is that first initial flat part of the lines, that is so-not-typical Bilstein. The rest is in line with their stuff - digressive curves and the more you crank, the more digressive it gets, the knee gets more and more pronounced. If we assume (but can we?) that the curves are really correct, it looks like all you adjust is the values, but not the shape of the curves. You will basically have always more or less the same digressive damper, and all you do with the clicks is increase the pressure, but not the character (behavior) of the damper. It will be great setup for super-smooth track use.


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## eggroller (May 25, 2000)

*Re: Putting the things together - Part II (pyce)*

Pyce...do you need an Eibach Pro Dampner to test? I have mine out of my car after 35K+ miles. I have replaced them with my Bilstein PSS9. Please let me know how I can contribute. Thank you!


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## pyce (Nov 7, 2001)

*Re: Putting the things together - Part II (eggroller)*

Ray, absolutely! That damper had been so famous for the great ride and sophisticated feel - we have to put it on the dyno and see what it looks like! You pay the shipment to me, I pay the return and will cover the dyno. Send me IM and we exchange addresses. http://****************.com/smile/emthup.gif


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## eggroller (May 25, 2000)

*Re: Putting the things together - Part II (pyce)*

Subjectively, they felt as they ran out of spring and used the secondary springs (bumpstops) quite quickly. I liked them a lot since they were quite controlled for the street. 
I am a different place in my driving life (lots of trackdays) and want something with more control as well as consistency. So, now I have the PSS9 coilovers. If they are anything like the H&R dampners then they probably have a linear response. 
I will ship the entire side (front and rear springs/dampners) to you. Too bad I didn't think to send you the PSS9 setup before I installed them.


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## alexb75 (Dec 29, 2002)

*Re: Putting the things together - Part II (pyce)*


_Quote, originally posted by *pyce* »_Continue from above ….
5. Now here is the fun part! Making a valving for the Koni that will make this 300 lb/in rear spring ride nice! It is hard to believe that a strong spring cane be made to ride nice, because the perception had been forever that springs to contribute a lot to the ride harshness in a car, but comes out it is not quiet the case. Yes, a stiffer spring will always ride harder than a softer one, but the difference is not any near as much as one would think. As posted few posts ago, everyone can try on an A4 to disconnect one of the rear dampers and go for a spin, concentrating on what that damper-less wheel is doing. The whole feel that there is actually a wheel and tire and contact with the surface disappears. I tried it with the stock 120 lb/in spring and then with the 300 lb/in H&R spring and the difference is not big – the feeling is that you are actually on 3 wheels, as the fourth one follows the surface without transferring anything to the chassis. So we put the Koni V5.0, which is the progressive damper we talked about just before on this page, the one that has very low and quite linear initially and then slowly becomes progressive compression curve. Looking at where the rebound from the H&R Damper is, it also came pretty clear that you do not need mega-rebound to control that spring, so from comparing the graphs it comes that the Koni rebound should take care of the 300 lb. spring at about 20% to 25% from full soft. We set it at half turn, which should be about there and the dampers went in….
6. The results is, as no one is going to believe it, OE ride quality! Bingo! Yes, it sounds nuts, but hey, I am in the Bay Area and everyone is free to come for a ride. There is little pitch at very high speeds on some surfaces, but that should be result of the twice as stiff rear-to-front spring rates, and anyway it is on speeds that the car is not normally driven. Things will settle once stronger springs go in the front too. I also feel that the rebound we put (25%) is little bit on the low side for fun drive, so perhaps will bring it up to about 30-35% this weekend and see what happens. But those are small details that are of no worries. The important part is that this rear is actually very smooth on the concrete, which is where I usually got the issues with other suspension setups. The only real issue so far is that the car rides like a real Cadillac; there is almost no feel for what is going on the surface below the tires and I am absolutely sure many will dislike it because of that. Basically, I think we hit the sweet spot for absolute comfort (can’t really imagine a 300 lb spring to be comfier than this!) and now have to start backing it off and start trading some comfort for feel, so the car actually feels sporty instead of lust flying into the corners in a boring and character-less way. The road holding is outstanding, but the lack of feel makes you think: “this can not be true!”. Just try to picture a bone-stock Jetta that stays flatter in corners and has significantly less under steer – that’s the car now….


Quite simply amazing! But Peter, could you please tell me then why you were always complaining about stiffer rear springs in the past? Rememeber the different shine ones that were no bearable comfort-wise? Was it the unmatched shock setting that made it ride that bad? These seem to be stiffer than shine and you are getting good results... interesting to know the difference.


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## pyce (Nov 7, 2001)

*Re: Putting the things together - Part II (alexb75)*

Because in the past I never took dampers as serious contributor to comfort. And you can actually get some decent comfort even with the "wrong" damper, but you have to reduce the spring rate so dramatically, so the damper gets a lot more load and the ride quality improves some. But it is really not about the springs, not at least about the relatively small variation in rate we make. You can talk to ex-Shine owners who take out the springs and keep the Bilsteins - they will tell you how surprised they were that the whole thing did not change as much as they thought (comfort wise). Springs are not as stiff as we perceive them when paired with a damper that works against the spring. You make that damper work with the spring - you get decent comfort even with double and triple the rates. I have taken ride in tour car, you were at 50% rebound back then, if I remember correctly, with SofSport. I am at the same 50% rebound right now, but very modified compression curve, and 300 lb rear springs, and my ride is very different than yours. None of my usual passenger recognized I did something to the rear (as per going from OE spring to 2.5 times stiffer!). In the past they notice if I change a damper, so that says some of the story. The full story is to take a ride. Come visit me, I am one day drive from you, come on


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## alexb75 (Dec 29, 2002)

*Re: Putting the things together - Part II (pyce)*


_Quote, originally posted by *pyce* »_I have taken ride in tour car, you were at 50% rebound back then, if I remember correctly, with SofSport. I am at the same 50% rebound right now, but very modified compression curve, and 300 lb rear springs, and my ride is very different than yours. None of my usual passenger recognized I did something to the rear (as per going from OE spring to 2.5 times stiffer!). In the past they notice if I change a damper, so that says some of the story. The full story is to take a ride. Come visit me, I am one day drive from you, come on









I might take you up on that offer







Might visit CA end of Aug.


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## silverbox (Jul 21, 2005)

*Re: Dampers (Occams_Razor)*

Indigo
Thanks for the post. I han thinking of reds for my 2003 tdi wagon.
are the part #s 87-2571 front......80-2815 Rear ?
Can you tell me more about the shine rear bar with OEM springs.
Thanks John


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## IndigoBlueWagon (Aug 9, 2004)

*Re: Dampers (silverbox)*

I am using the same parts as the sedan--don't know the numbers offhand. The wagon does have its own part number for rear reds, but they aren't imported to the US. It appears the difference is minor--slightly longer travel. I decided to go ahead and try the sedan ones--no apparent problems.
I had heard that Dick Shine recommended against using his sway bar with OE springs because the additional body roll (especially in the front with softer springs) would put too much stress on the bar and cause it to break. I know the bar has been modified somewhat and this may no longer be an issue. I'd call Shine and ask. Calling is quicker than email.


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## phatvw (Aug 29, 2001)

*Re: Dampers (IndigoBlueWagon)*

Wow just caught up on this thread. Good stuff Peter et all!
This is really interesting stuff. Peter where do you get all the time to work on this stuff? Just outstanding. You really ought to hook up with a marketting type and make some money from all your hard work. Pyce-brand dampers or whatnot...


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## pyce (Nov 7, 2001)

*Koni V5.0 and 250 lb/in rear spring .......*

Spent some time doing spring experiments this weekend (more on that in another thread later) and the accelerometer was already in the car, so decided to run the car and see what graphs we get with this new 250 lb/in rear spring and the latest Koni V5.0. Have been telling people that comfort is OE-like, but of course who’s going to believe, so perhaps the graphs below can be of help








This is the run with the 250 lb/in spring, same rear tire, same pressure, same car:









To note is that the rebound is set to 50%, which is around where the spring works best for comfort. Also to note that the car is now pitching quite noticeably, so I do not know how much of these lower amplitude lines are due to just pitch that should disappear when we later get the front to rear spring rates right. (front is stock 150 lb/in spring for now).

And here we have an oldie – the same car, but with stock 120 lb/in springs and Bilstein TC Sport:


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## pdcm (Mar 29, 2000)

*Re: Koni V5.0 and 250 lb/in rear spring ....... (pyce)*

The graph of the V5 valving looks nice with the 250 lb/in spring. I'm curious though, did you end up trying the H&R 'Dune Buggy' set with the fronts as well... or were you working to get the Koni valving to perform similarly, then try the fronts. I guess I should go back and re-read the last few entries. Thanks pyce for all your hard work!


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## pyce (Nov 7, 2001)

*Re: Koni V5.0 and 250 lb/in rear spring ....... (pdcm)*

The H&R Dune Buggy showed very disappointing rear spring rate results, and therefore I removed them and got something else, so I really know what the spring rate is. I was raving about the great comfort with H&R DB rear springs and there was reason for that - we tested them on a spring tester and the rate when compressed to installed height came to be a screaming 130 lb/in for the first inch of travel after installed height! It is a non-linear spring, so by compressing it more and more it slowly ramps on the coil, making it stronger as it goes down, but the second inch of compression showed 170 lb/in rate. At this point, with already two inches of travel, I decided to go no further. Perhaps the advertised 285 lb/in was meant with the bump stops (as they will give another 100 lb/in. at specific height), I have no idea. Perhaps, like many other things, those numbers were always pure rumors and you know a rumor becomes truth when said more than few times. Fact is, Dick was right, these springs are soft, so I have no interest in them anymore. Therefore the 250 lb/in (real rate!) spring came and now that is what I have in the car, which also works great (as seen from the graph above) but it could be done even better.


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## pyce (Nov 7, 2001)

*The OEM damper - not really as bad as you think!*

Time ago John A. got himself a set of Koni Yellow and sent me his used OE Sachs dampers (rears only) to dyno them and see how incredibly blown they are, taking into consideration that he has driven them (hard) for about 84.000 miles, and even worse, the last 73.000 miles of them were with lowering Eibach springs….. He has a Jetta WE (Wolfsburg Edition).
Here is the dyno of his rear dampers, in comparison to a pretty fresh (10.000 miles) Jetta TDI rear damper:









As you could all see, the difference is close to none, with the slightly higher values that belong to the older and “beaten” WE dampers! Especially as the velocity goes up….. Now of course, we have to find a pretty brand new WE damper as to see if there was some difference in the valving to begin with (meaning: the WE may have slightly higher values being considered a sportier trim). But who knows, the dampers may be valved the same as the rear springs from both cars are the same…. We will see, but definitely not bad for the OE damper with lowering springs








Stay tuned for the Eibach Pro Damper, coming next!


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## 2beirish (Apr 28, 2004)

*Re: The OEM damper - not really as bad as you think! (pyce)*

I've been away from this thread for a couple months because I sold my Jetta wagon (part of the terrible dealership problems the Len Hunt thread talks about) and figured the thread was VW specific. Now in a mint 88 BMW 325iS that had 34,600 miles in it when I bought it. Began suspension mods immediately. Please note that this 17 year old car was inherently more balanced and had better turn in (how do I quantify this?) and transition feel than the 2003 Jetta with Neuspeed softsports and Bilstein Sports I sold, even with a blown front shock on the BMW. I installed Ireland Engineering Stage 3 springs and Bilstein Sports on the 325iS quickly, as well as poly bushings and a host of other suspension mods. I wanted a car that was very stable in quick transition (like fast freeway ramp entry) and comfortable: both for my wife, who gets nervous in very quick reacting cars and likes cush. The IE springs (lots stiffer than stock: don't have the figures here-basically SCCA ITS class spring rate) and Bilsteins are much more comfortable than the stock springs except in first hit on big frost heaves. This car is stable and predictable on the track and comfortable on the street. I DO prefer RWD. I DID have to fuss with front and rear sway bar
stiffness (full stiff front, full soft rear) to get the rear stable (archaic E30 trailing arm independent rear suspension). This discussion has helped me with tuning both my FWD Jetta wagon AND the RWD E30 BMW, and challenged some of my beliefs about the way to set up cars. I AM in northern California, frequently in the Bay Area visiting my aged Dad-in-Law, so if someone wishes to drive an RWD modded car to compare to the results of the testing on the VWs, please IM me and we can meet. Thanks much for all the very sound thinking and learned experimentation here, as well as keeping it somewhat layperson friendly technically. I've read every page of this thread and understood a high percentage.


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## Occams_Razor (Jun 28, 2003)

*Re: The OEM damper - not really as bad as you think! (pyce)*

Bump to get this thread back in my watched items!


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## John A (Feb 19, 2001)

*Re: The OEM damper - not really as bad as you think! (pyce)*


_Quote, originally posted by *pyce* »_










I'm stunned!








I thought they'd be much, much worse.... damn. 
THANKS Peter!


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## pyce (Nov 7, 2001)

*Re: The OEM damper - not really as bad as you think! (John A)*

John, looking at how they are not bad at all - would you like them back?







I was thinking to cut them and see if the valving is any different than the TDI dampers, but they look so good, I feel bad cutting them now, LOL!
Edited to add: 2beirish, let me know when you are in the SFBA next time and I can show you the dyno shop, etc. We can also test drive some cars, etc.


_Modified by pyce at 11:28 AM 8-31-2005_


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## silverbox (Jul 21, 2005)

*Re: The OEM damper - not really as bad as you think! (pyce)*

I spoke with Kenny in tech support at Sachs NA yesterday, asking him wether Sachs made a damper for the A4 platform with higher damping forces. He said that later this year they will be making dampers for the NB sport. he said this damper is about 20% stiffer. Given the high quality design and build thats been discovered about OE sachs units, this might be an option for street performance.


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## pyce (Nov 7, 2001)

*The Mighty Eibach Pro Damper ....*

As promised, here is the dyno from the Mighty Eibach Pro Damper! Mighty, because it had been said by almost all owners to be the real reason for the amazing feel of the Pro Kit, for the great control and great comfort. There is even huge thread in the FAQ, dedicated entirely on this Kit. The damper had been described as progressive, specifically tuned for the Kit, etc. Here we go:








As we can see from the Force vs. Displacement graph, the damper is actually quiet linear at low speeds and becomes digressive at higher speeds. It is also interesting to note that the compression-rebound ratio is not as disproportioned as on other popular dampers. Especially on the low speeds, we have almost identical values for compression and rebound, or if not really identical - very close at least. Comparing it to the other contenders from the popular aftermarket sector, it is pretty clear that this damper was designed with one goal in mind - comfort for a Kit that would use well defined soft springs. How is that, you would ask? Well, the high compression (in comparison the rebound) is there to help the softer spring and make the car ride "higher" over bumps. Higher compression help the spring (when driven over a surface that makes the damper move up and down a lot) to extend little bit more as the damper "jacks" the spring up (or at least does not allow the spring to compress too much down due to the series of bumps). Basically, you drive on smooth road and the car is low, sitting nicely on the buffers, smooth and enjoyable, great feel and response..... then you go over series of bumps and the high compression (relative to rebound) makes it that the car get "jacked" up little bit, so it does not bottom so badly while crossing those bumps and once the bumps are over, the car sits back low where it was for the next smooth stretch. No wonder Eibach Pro Kit owners talk about Audi and BMW feeling, superb comfort, etc. Yes, the comfort that also comes from the very little rebound, designed in this damper. It really is "specifically designed to work with this spring". It is really a Kit, something well calculated and tested to achieve specific goals. This is perhaps the first damper that we can say is "matched" to the spring it has to work with. Now, some may argue that it is too soft, so there is no performance, etc. but those are personal things that everyone should decide for himself. Fact is, the Kit was put very well together with the goal to transform the VW A4 into a comfortable, lowered, with more in-control feel car and from the graphs and the spring test I am pretty sure it does the trick very well.
Here is a small comparison between the Pro Damper and John's used OE rear damper from the Jetta WE:








It is pretty clear (and it is the same on all other speeds, I just did not include them as to make it easier to read the lines) how the WE always has stronger rebound and the Pro Damper always has stronger compression (and by quiet a lot!) especially at the higher speeds.
For the records, here are the results from the spring tester:
Eibach Pro Kit Front spring - 110 lb/in (very linear)
Eibach Pro Kit Rear spring - 110 lb/in (very linear)
We all should thank Ray eggroller for shipping the Kit for the test!


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## ruking (Apr 4, 2003)

*Re: The OEM damper - not really as bad as you think! (pyce)*

Dear Pyce,
Thanks for the experimental and testing work on the stock oem Sachs with 10k and 84k miles! Your objective testing confirms my SOTP experiences and guestimates that the oem SACHS dampers did not deviate from NEW as much as most people either had perceived or thought. I had made the decision to keep the oem Sachs shocks to at least 100k and your testing in effect indicated that it is very do able. I do still have the unused Bilstein TC's (for 2003 VW Jetta TDI) if anybody might be interested.


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## eggroller (May 25, 2000)

*Re: The Mighty Eibach Pro Damper .... (pyce)*

Well, yes the Eibach Pro System is a comfortable kit. The kit I sent you has about 40k+ miles on them. I liked it until I was racing more. I didn't feel as the car was in control. Now I have the PSS9. I should have sent the PSS9 kit to you before I installed them. 
Pyce, Thank you for all of your contributions to the Vortex community!


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## missmy8716v (Apr 8, 2005)

*Re: The Mighty Eibach Pro Damper .... (eggroller)*

Excellent work here! I ran the Pro system in my 2002 Jetta wagon & liked it & I'm now thinking about using it in my 2005 Passat wagon. Is this a good choice or should i wait for the ner Koni FRS dampers? IF I go Koni, what springs should I use? The car seems quite high stock & I don't believe a drop of 1.2 in. or so would affect the gemetry too much nor hinder ground cleareance for driveways & such. What do you think Pyce?


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## missmy8716v (Apr 8, 2005)

*Re: The Mighty Eibach Pro Damper .... (missmy8716v)*

Sorry for the spelling! It's late & I need to go to bed!


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## pyce (Nov 7, 2001)

*Re: The Mighty Eibach Pro Damper .... (missmy8716v)*

You have a better chance if talking to Passat owners with such system. Start a topic in the Passat Forums and I am sure someone will tell you more about it. It really isn't about what I or anyone else thinks when it comes to "which suspension to run". It is a personal choice, you get what you like, so you are happy about it. Spring rates are used to tune the suspension, but it really does not mean that if someone has softer springs is less of a man. I am pretty sure sooner or later someone will say: "I loved my Eibach Kit for years, but now that I know the springs are softer than stock, I do not like it anymore!" But it really should not be like this. If you like what you got, then just enjoy it and who really cares about the number.


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## missmy8716v (Apr 8, 2005)

*Re: The Mighty Eibach Pro Damper .... (pyce)*

Thanks Pyce. I was just looking for some suggestions because you've tested some many set-ups. Thanks again as I could never afford to try all those on my car & now I don't have to. I just want to make sure I don't go too low as to be on the bumpstops all the time & I know the Passat suspension is different than the A4 stuff you're testing but the products all come from the same manufacturers & I bet the results would be similar. I think I'll wait for the Koni FSD's & try to find some suitable springs for them as the stock ride height is killing me visually! Looks like a Passat Allroad!


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## Max Rebo (Apr 11, 1999)

Here's something recent:
http://forums.vwvortex.com/zerothread?id=2011200
US-OE Monroe--- (hopefully the pic owner won't mind)








I won't post the other graphs, as they are in the linked topic. I found the above graph interesting... and a bit disturbing.







In the topic above, the OE Monroes, Euro OE Bilsteins, Bilstein Sports, and Konis (full hard, full soft) are compared.
Take a look at the shock dyno for the US-OE Monroe damper. Anyone who has an R32 is probably familiar with the mushy-floaty feeling of the stock suspension, especially once they have accumulated 10-20k miles. It's okay while driving on smooth roads, but once you start turning, hit some bumps or dips in the road, the suspension feels unstable. Based on the high-speed compression/rebound curves, I can see why it feels like the car "crashes" over abrupt bumps in the road.
I recently upgraded to an Euro-OEM suspension. As you can see from the link above, the Euro-Bilsteins are valved a bit stiffer than the normal Bilstein Sports. Regardless, with the new Euro-OE H&R springs and Bilstein dampers, the suspension feels much smoother, better balanced, and much more stable.


_Modified by Max Rebo at 12:08 PM 9-5-2005_


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## pyce (Nov 7, 2001)

*Re: (Max Rebo)*

They had to do the rebound that way. Strong digressive rebound brings a lot of discomfort and the car after all is for all sorts of people. Plus, look at the roads where some drive, pure disasters. Put on top of that stiff springs and big wheels - the damper had to be set for comfort first. Then those like you who need more, go for the aftermarket stuff. 
I would love to put my hands on a rear damper from R32, to cut it and find out how they have done the "dual stage" rebound. If anyone really hates his rear dampers and plans on throwing them away, please IM me and I will get them. Thanks.


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## Max Rebo (Apr 11, 1999)

It's not labeled, but the bottom rebound line is (I assume) 30 in/sec. Based on that graph above, is that why it feels like my car "crashes" over abrupt bumps in the road? It was really uncomfortable. The US-spec suspension felt very floaty and somewhat unstable going through twisty roads.


_Modified by Max Rebo at 1:11 PM 9-6-2005_


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## pyce (Nov 7, 2001)

*Re: (Max Rebo)*

Describe the "crashing", please! It is very important to differentiate impact crash from "landing" crash. Too much rebound is some times a lot worse than too much compression, but it is not so intuitive, so people "over-rebound" their cars and get so crappy ride, thinking that is their springs that are too hard, etc. Reducing rebound makes miracles with ride quality, but then you get the exact feeling you were talking about in the second part of the post - "floaty" on twisty roads.
Looking at the compression of the R32 dampers, the higher the speed (shaft speed that is), the more digressive it gets and the "knee" is quite pronounced. That definitely does not help with impact harshness either. But at the same time, it is performance car and people would have hated to have more dive and squat that would have come with more comfortable compression curve.


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## Max Rebo (Apr 11, 1999)

*Re: (pyce)*

To me, it seems the "crash" sensation is from the initial impact. The landing (from rebound?) is okay.
I now have the full Euro-OEM suspension (Bilstein, H&R), and the impact harshness is significantly reduced. It actually feels more comfortable than the US-spec OEM setup, although I know that it is subjective.


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## Max Rebo (Apr 11, 1999)

*Re: (pyce)*


_Quote, originally posted by *pyce* »_
I would love to put my hands on a rear damper from R32, to cut it and find out how they have done the "dual stage" rebound. If anyone really hates his rear dampers and plans on throwing them away, please IM me and I will get them. Thanks.

Not sure if you saw my IM yet, so I'll reply here as well.
I'll gladly donate one of my US-spec R32 rear dampers. I hate these things with a passion.


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## eggroller (May 25, 2000)

Pyce, I am thinking about shipping you 1 of my rear PSS9 dampners to dyno. In the meantime, I could shove the eibach dampners on the car. Wadda ya think?
The dyno is not going to wear them out are they?


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## pyce (Nov 7, 2001)

*Re: (eggroller)*

Sure, send it. You can use any dampers meanwhile. OE VW would be better than the Eibach as it will have slightly more rebound and less compression, which is what you would need with stiffer spring.


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## eggroller (May 25, 2000)

*Re: (pyce)*

Peter, you have an IM from me concerning the address to ship a rear PSS9 dampener (again). 
Paul (Traffic) and I did a swap-fest of rear dampeners tonight. I put the Bilstein HD dampeners in the rear of my car from his. He put the Bilstein TC dampeners in his car. We left the '03 OEM dampeners on the garage floor for now.
*My car*
Front has Bilstein PSS9 front dampeners with the spec springs (~400 ft-lbs springs). Rear has Bilstein HD dampeners with the PSS9 spec springs (supposed to be 250 ft-lbs or so)
<driving it more to provide a more through review)
*Paul's car (Traffic)*
Front has Bilstein HD front dampeners with the Neuspeed Softsport springs. Rear has Bilstein TC dampeners with the Neuspeed Softsport springs.
*(this review is just from initial impressions.) *For compression it felt like #8 on the PSS9. Takes the initial hit and then falls of a bit. For Rebound it felt like there is better rebound control than the Bilstein HD. It just was not enough for the spring rates his car has. Felt quite smooth. The dampners did not help much with the roll of his car on the turns. 


_Modified by eggroller at 11:38 PM 9-24-2005_


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## traffic (Sep 23, 2003)

*Re: (eggroller)*


_Quote, originally posted by *eggroller* »_
For compression it felt like #8 on the PSS9. Takes the initial hit and then falls of a bit. For Rebound it felt like there is better rebound control than the Bilstein HD. It just was not enough for the spring rates his car has. Felt quite smooth. The dampners did not help much with the roll of his car on the turns. 

Don't you mean less rebound with the TC than the HD? I like the softer initial hit on bumps with the TC. But felt the bounce back more with the TC. Not a bad setup for a DD. Better than my HD I think. But there was a lot more movement with the TCs when the pace was turned up in the corners. Took just a fraction of a second longer to take a set when transitioning as well.


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## traffic (Sep 23, 2003)

*Re: (traffic)*

BTW, I can't tell you how fascinated I am by the small differences in the various setups and combinations. There's no way to compare them unless you literally go back to back with it. But the little differences become big the longer you drive.


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## pyce (Nov 7, 2001)

*Re: (traffic)*

I hope you two will drive the cars like this for at least three days! An evening for a test is really not enough. Three days later, when life gets back to routine, the difference between what you two are so used to will be huge. Since this thread started and every damper when into the car, my first night impressions have been always somehow skewed compare to the final verdict days later. Traffic said it very well: The little differences become big the longer you drive. Please, keep the setups this way and drive it for even a week. Drive it until you are so certain of the things you hate about them


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## pyce (Nov 7, 2001)

*Calling the PNW guys!*

Just got back from the dyno. We had Ray's rear PSS9 damper. It is very late, so we tested it only on #1 (full stiff) and #9 (full soft), as the rest is a range in between. Anyway, Phil will do the rest tomorrow and will ship the damper back, so, Ray, you should have it in 5 working days. I would like to thank you very much from providing the damper for this very important test!








Phat, Traffic, Ray ..... Let's try to do it differently this time! Instead of posting the dyno, I would very much appreciate if you three of you can come out with pretty detailed description on the PSS9 ride quality in comparison to the rest of the dampers your are trying. It is not going to be easy, as you did not try all springs with all dampers on all three cars, but let's try to have some sort of at least subjective description, or sort of ranking, among everything you guys have tried so far. Ideally, you three would even try to predict the damping curves that the PSS9 would provide, compared to the other dynos we had so far, based on the feel you got from the rides. I know maybe I am asking too much, but try, please! It is very important, because the PSS9 curves and values are something that proves many points discussed in the past, but that time was just theories - now it is reality, so we need your real life experience to boost the dyno curves you are going to see later







Thanks a lot!


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## eggroller (May 25, 2000)

*Re: Calling the PNW guys! (pyce)*

Thanks to you & the crew, Peter!!! Looks like we have some homework, guys!!!


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## traffic (Sep 23, 2003)

*Re: Calling the PNW guys! (eggroller)*

All in the name of science!!








Peter, Ray and I were just discussing something like that. Our next test was going to install the rear PSS9 in my car wtih Neuspeed softsport springs and play around with the different settings. We wanted to dial in the best setting given a much softer spring and see how it compares to the off the shelf shocks, like the Bilstein HD. I'm not sure how it would do in performance, but my guess is that the comfort would go up a bit since it doesn't have that kink in the curver like the HDs.
IDK if there is a way to contact another local dubber to borrow a set of KONI yellows.








Hey Dan, did ya hear that? It's my turn to run Pyce's Shine springs!!



_Modified by traffic at 7:31 AM 10-3-2005_


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## phatvw (Aug 29, 2001)

*Re: Calling the PNW guys! (traffic)*


_Quote, originally posted by *traffic* »_All in the name of science!!








Peter, Ray and I were just discussing something like that. Our next test was going to install the rear PSS9 in my car wtih Neuspeed softsport springs and play around with the different settings. We wanted to dial in the best setting given a much softer spring and see how it compares to the off the shelf shocks, like the Bilstein HD. I'm not sure how it would do in performance, but my guess is that the comfort would go up a bit since it doesn't have that kink in the curver like the HDs.
IDK if there is a way to contact another local dubber to borrow a set of KONI yellows.








Hey Dan, did ya hear that? It's my turn to run Pyce's Shine springs!!
_Modified by traffic at 7:31 AM 10-3-2005_

Hey I'm keeping those shine fronts, mang! Can't keep going in for alignments all the time







But I'll swap whatever rear stuff we need to! We really should invest in a camber gauge and those big toe alignment plates...
Whats the plan for tech day this weekend with _3-crubs racing_?


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## eggroller (May 25, 2000)

*Re: Calling the PNW guys! (phatvw)*

Just found out that a fellow Vortexer locally has the Camber gauge and Toe plates!



_Modified by eggroller at 11:50 PM 10-4-2005_


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## mitsui14sun (Mar 26, 2005)

*Re: Calling the PNW guys! (eggroller)*

Moe has those, silly


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## jasonTDI1 (Jan 24, 2004)

*Re: Calling the PNW guys! (mitsui14sun)*

I have had the Pro Eibach kit for 94K miles. The first 50 were great. then it's been steadily downhill. They are about to come out. Chicago and WI roads just KILLED them. They are positivly SCARY, WAY over sprung now. the car bounds all over the place. 
One question. Anyone know if the TDI wagon rears are higher range? I hauls a LOT of tools to work ion TDI's (250-300lbs) all the time and want to keep the rear from dragging. Any suggestions would be helpful. I'm going back to stock on the front probably. Looking for those too. 
TIA


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## robnitro (Feb 13, 2004)

*Re: Calling the PNW guys! (jasonTDI1)*

Hi Jason
I run the tdi wagon rears in my car. They are taller so it was like a 1 inch rear lift. But not too much harder. They will prevent sagging... 
I stiffened up the rear and made it a bit shorter by clamping 2 coils together using autozone clamps and that did a great service. Now I have very neutral handling, none of that understeer push. 
I have a lift kit almost 2 inches all around and wagon springs all around... with TC sport all around. The NYC potholes are a bit harsh but I don't lose control like I did with the stiffer Sports and autotech lowering springs I had (from LAST OWNER- Doh.. horrible understeer btw). It was amazing how the autotech springs seemed softer than even these wagon springs. I guess its somewhat progressive. 
Maybe the extra suspension travel from the lift kit and rear shock extenders makes it a bit gentler?


_Modified by robnitro at 7:53 PM 11-1-2005_


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## eggroller (May 25, 2000)

*Homework Assignment - Subjective dampner assesments*

It has been a while. We (Crub Racing - PhatVW, Traffic and myself) have been testing different dampers in our respective cars for extended periods of time. The folllowing items are what we will/have tested:
Bilstein PSS9
Bilstein HD
Bilstein Sport
Bilstein TC
Koni Red
We are not finished testing yet but I would like to get the ball rolling by posting my impressions of the 1st two items. 
*Bilstein PSS9*
<-1------------9->
<-stiff------soft->
Very linear response for both compression and rebound.
Initial impact is not harsh however the ramp up to stiff is consistent for compression. These are a part of my PSS9 suspension. Of course I love them. The adjustability allows for my 'comfortable' daily drive on all sorts of pavement/situations. For daily driving the front dampers are at 6 and the rear at 8. When I test other dampers I leave the front at 6.
*Bilstein HD*
Non-linear in compression response. Prettly linear rebound response.
For compression, these 'feel' very stiff initially. Small bumps are felt, a lot. Then when you hit a large bump the compression damping 'dies off'. Initial feel is about equivilent to a 5 or 4 on my PSS9. Then it falls off to a 9 or worse.
The rebound is a different story. They feel as they are stiff than the PSS9 initially then they 'die off'. Overall, the rebound feel is similar to the 8 setting on my PSS9.
------------------
More to come soon....I will get the Bilstein Sport from a friend, soon. He has petitioned to be a part of Crub Racing. We are allowing him to be an honorary member. However, he needs some training on the track before I consider him a member....hear that Gaki?















Traffic, please re-post your data about the Koni Reds. Get those PSS9 installed!!! PhatVW...time for some Konis!
EDIT: Added Bilstein TC to the list. 
EDIT2: Fixed some spell'n errors. LOL.


_Modified by eggroller at 7:20 PM 11-7-2005_


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## Mikes72sb (Oct 27, 2001)

*Re: Homework Assignment - Subjective dampner assesments (eggroller)*

First off, what a great thread http://****************.com/smile/emthup.gif It's nice to see an exchange of REAL information.
I figured that I would post my suspension experiences so others can read it and maybe it'll help out a little bit.
I ran Eibach Pro-Kit springs with Bilstein TC sport shocks for almost a year/5000 miles, give or take. At first I thought it was a good setup, but after a while (when I started to commute to NJ) I started to realise and dislike the harsh initial compression of the TC. I decided to save for some better shocks, and recently purchased and installed Bilstein Sports with my Pro-Kits. I've driven it a fair bit in the 4 days I've had them installed (highway and city) and I find that this setup is much smoother and more comfortable then my old setup. They're smoother over bumps and much more controlled over series of bumps. Also, I noticed a definite increase in handling and steering response.
Of course, time will tell, but so far so good http://****************.com/smile/emthup.gif


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## traffic (Sep 23, 2003)

*Re: Homework Assignment - Subjective dampner assesments (Mikes72sb)*

Ok, so I've been working with Ray, Pyce, NS01GTI, (Dan needs to get going on this too!) on experimenting with different shocks on my car. I'm running softsport springs all around and Bilstein HDs in the front on a vr6 gti.
First I want to say that it's amazing how just changing the rear shocks on my car can have such an impact. It's the difference between hating the drive to finding it quite pleasurable as a daily driver.
*Bilstein HD*
So these are the first aftermarket shocks I installed with the springs. They are great for handling and is livable for commuting. Full bumpstops on the softsport springs rides stiffer than with cut bumpstops.
The fast reacting damping makes the small bumps irritating. But when you hit a larger bump, it actually feels better than OEM.
*PSS9*
I am currently running the PSS9 rears set to 8. I have to agree that compared with the HDs, the initial stiffness is not as harsh, but it progressively gets stronger as the bump or dip becomes larger. On small bumps, I prefer the PSS9, on larger bumps, I prefer the HD.
In terms of handling, too short a time to tell. But some quick turns tells me that I don't think I'm losing much if any in terms of handling. Again, my focus is more on comfort versus handling.
*Bilstein TC (sport)*
Pyce sent these to me to try out. I found the initial impact to be a bit softer than the HDs. But the rebound was too soft; it was not controlled enough. I felt like I was bouncing back from larger bumps. Still, the softness of the initial impact had me feeling I'd rather run the TCs instead of the HDs for comfort. It's definitely an OEM replacement shock.
The TCs had quite a bit of movement in the handling department. I always had to allow a bit longer to take a set. I had to be extra smooth as well as small changes really disrupted the chassis.
*KONI reds*
NS01GTI decided he'd like a set, but sent them to me first to get my impressions and try tweaking the various settings and compare with other setups.
The compression damping seems to be very good for my springs. The more linear response felt much better than the HDs. But what opened my eyes was the small adjustments in rebound.
I had been an advocate for strong rebound damping. But I didn't realize how close to "too much" I was. I original started at 90 degrees from full soft (out of 720) Initial impacts felt better than HDs (I'm starting to think that anything has softer initial impact than the HDs) and the rebound was well controlled. No bounce back whatsoever.
What I didn't realize was how much the suspension was being packed down by having the rebound set too high (thanks to pyce for pointing that out) So by packing the suspension, I was compressed down to the bumpstops before I'd hit the next bump, then I would immediately ride on 700lb bumpstops. No wonder it felt like I was almost bottoming out. I probably was.
Since then I've tried 0, 30, 45, 60, and 135.
0 - Too much movement for me. It wasn't as bad as OEM. Probably closer to the TCs. Maybe just a hair more movement than the TCs. But I like the compression damping better than TCs. Just felt smoother as the damping increased.
30 - My last setting. I would say this is the softest I'd go. The rebound was right on the border of controlling the movement. I felt like at this setting, the suspension was 'free' to move up and down the most without feeling like I was pogo-ing back from bumps.
45- I like this setting the best. It's a hair more controlled than 30. It's a really good balance. I feel like the suspension can move as much as it can, but still keep things in control. The handling is not bad either. It's not as good as the HDs for sure. But for most people, I think they would be very happy.
60 - Now we're starting to get a little too much rebound. Especially with a stiff RSB like the Shine, slow speed over irregular pavement had me bouncing left and right more than I'd like. I felt the suspension packing down. The control was a touch tighter. But I never felt like it was HD levels.
90 - I don't remember. This was the first setting I tried almost a month ago. Obviously I felt the packing down sensation.
135 - Don't know if there is THAT much difference. I'm already packing the suspension down. It's secured on the bumpstops. Yet I'm not letting the suspension rebound (much.) Incidentily, I still didn't feel like it handled as well as the HDs. Even with going to such a stiff setting. My guess is that the damping isn't mated correctly so it's just stiff, not necessarily better.
Comparing the KONI reds and the PSS9s, I'd have to say that 60 degrees on the reds feel like setting 8 on the Pss9s. Although for some strange reason, I just like how the PSS9s go about damping. It feels like it's stiff but I have more suspension travel. I will try the PSS9s on 9 on the drive home.
Stay tuned.


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## NS01GTI (Jan 31, 2005)

*Re: Homework Assignment - Subjective dampner assesments (traffic)*

Good write up Paul. Sounds like the reds are nice upgrade for a daily driver providing a nice blend of upgraded controlled damping and comfort, while the PSS9s maintain pretty good comfort while acheiving higher level of handling control.


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## traffic (Sep 23, 2003)

*Re: Calling the PNW guys! (phatvw)*

Ok, I set the PSS9 to 9 (full soft.)
I'm a bit confused. I expected the damping to less, but I seem to feel a bouncy ride. What's confusing is that it feels like I have higher spring rates with this shock than with the KONIs.
It's a bit of an underdamped feeling. There is quick movement of the suspesion when I go over bumps. Nothing harsh. But I feel like there's a lot of velocity involved. It's not the same as the KONI reds on full soft. The bumps were soaked up well, but then I would feel, not a pogo-ing affect, but just the chassi would not settle. It was constently moving just a little bit. I almost felt a tad sea-sick.
The PSS9s would bounce me back quickly. But it's not like it's oscillating. I don't feel sea sick, but it is uncomfortable that I'd be bounced back so quickly.
When turning into a corner, I still felt more in control with the PSS9s than with the KONI reds set to 30-45. Now I really didn't have mid corner bumps in my short drives, so no telling how bumps would impact things in a corner. But on relatively smooth corners, it seem to settle quickly and stay planted. Turn-ins were still very sharp.
For a daily driver, I think I might click back to the 8 setting. But I'll try 7 tonight on the way home.
here's one of Peter's graphs for reference.


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## mitsui14sun (Mar 26, 2005)

*Re: Calling the PNW guys! (traffic)*

My car is a bit different with Pss9, but I will play too


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## traffic (Sep 23, 2003)

*Re: Calling the PNW guys! (mitsui14sun)*

Ok, so I've had an opportunity to drive around on setting 7 and much more time on setting 8 of the *PSS9*s.
*On 7*, the ride feels very stiff. Motion of the springs is definitely impacted. I get more bouncing from my "street" inflation settings on my tires.
But, boy can I corner now. I would take a corner similar to my HD setup and feel like I have a little more grip.
It's definitely different than just cranking up the rebound on the KONIs. I can feel both compression and rebound are controlled. Whereas the KONIs would be packing the suspension down to the point the spring rates are increased.
But I couldn't stand too much of this setting for normal street driving.
*Backed it down to 8*. Seems to be a good balance of damping.
HOWEVER, this weekend, I was in downtown Seattle with lots of old concrete sections as well as rippled asphalt where the busses hit their brakes. oye!!! Too much spring rate and damping with not enough travel. I think the PSS9s definitely has higher rate bumpstops than OEM. The HDs with the cut bumpstops did much better with these big bumps.
I don't think I could run this setup if I had to deal with these types of roads all the time. My wife finally asked why my suspension is so uncomfortable.








Ray, good thing you and I live near mostly good roads. I don't think I could sacrifice this much comfort for even the amazing amount of control you get with the PSS9s. Well,...maybe if I did more track days, I might be able to do it.
Ah...but that's where the KONI reds might come into play.


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## phatvw (Aug 29, 2001)

*Re: Calling the PNW guys! (traffic)*

Hehe Paul. Now you see the roads I have to deal with every day. Whenever I drive somewhere with the woman, we take her stock Jetta GL 2.0.
BTW what bumpstops are on those rear PSS9's? I don't think I've ever seem em up close. I thought they were just the regular oem bumpstops just like any other damper.Is it actually a special piece from Bilstein?



_Modified by phatvw at 12:56 PM 11-14-2005_


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## eggroller (May 25, 2000)

*Re: Calling the PNW guys! (phatvw)*

The bumpstops are internal. The rear shocks....well...looks like shocks. They mount directly to the aluminum piece to the body. Think of it as inverted Bilstein HD with a blue shock boot at the bottom.
Paul, I know the feeling of the shocks reaching the bumpstops. However, don't forget Pyce's dyno. The curve continues to ramp up! I am willing to live with such shortcomings because we don't have so many bad roads around where we travel.


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## traffic (Sep 23, 2003)

*Re: Calling the PNW guys! (eggroller)*

Ray,
When do we grab Gaki's Bilstein sports?


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## GTIMOLA (Mar 19, 2004)

*Re: Calling the PNW guys! (traffic)*

Hey, when you guys decide on what is the "best" please IM me. I'm not going to spend any money until then














.
Bump for a great thread.


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## eggroller (May 25, 2000)

*Re: Calling the PNW guys! (GTIMOLA)*

Well, depends on what you are willing to endure and what your goals are. I spent the money on the PSS9 because I like to track the car and willing to compromise on street comfort. Funny thing is, I believe big bumps are soaked up better on the PSS9 suspension than the Eibach Pro System. More suspension travel and better compression damping!


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## silverbox (Jul 21, 2005)

I think it was this thread, quite a while back, people were talking of a real grand touring suspension.
So I wanted to let people know I've installed Koni FSD shocks on my otherwise stock Jetta wagon. I've only had them on for 2 days, but wow! It's hard to believe a ride this smooth could be so controled. We have lots of bad roads in Nova Scotia and i can say these shocks are smooth.
As for control, last night winds were gusting to about 100KM per hr and it was raining hard on the highway the car felt like it was on tracks.
My first impressions are good. Tomorrow and friday I may be going on a few short road trips, I'll report back again.


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## AMR Engineering (Jun 7, 2006)

*Re: (silverbox)*

Not sure how old this thread is, but I found it in google search. Great info, but I am curious to why you guys did not dyno a full coilover system rather than these oem replacement shocks. I guess I can't really call them OEM, but u know what I mean.


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## briang (Mar 10, 1999)

*Re: (AMR Engineering)*


_Quote, originally posted by *AMR Engineering* »_Not sure how old this thread is, but I found it in google search. Great info, but I am curious to why you guys did not dyno a full coilover system rather than these oem replacement shocks. I guess I can't really call them OEM, but u know what I mean. 

The goal of the OP was to find stock ride and killer handling...thus he tested items that might meet his goals...


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## Ripdubski (Aug 12, 2004)

Wow! Just found this thread and after reading for several hours, WOW. This is what forums are all about. This thread has helped me decide on Koni Reds for my 98 VW Cabrio with Neuspeed SofSports.
Great work!


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## GoFaster (Jun 18, 1999)

*Re: (AMR Engineering)*


_Quote, originally posted by *AMR Engineering* »_Not sure how old this thread is, but I found it in google search. Great info, but I am curious to why you guys did not dyno a full coilover system rather than these oem replacement shocks. I guess I can't really call them OEM, but u know what I mean. 

Most "coil-overs" that are supposedly meant for these cars don't allow the car to operate near stock ride height, and that has other adverse effects which have been extensively discussed in other threads. In any case, "coil-over" simply means that the coil spring is installed around the shock body, THAT'S ALL. There is nothing inherently magic about doing that. The magic is inside the shock's valving, and for that, it doesn't matter one iota whether the coil spring is wound around the outside of the shock or installed separately.


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## abawp (Nov 30, 2005)

Has a set of KW adjustable shocks been on the shock dyno yet?


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## TeoIntegrale (Mar 18, 2007)

*Re: Homework Assignment - Subjective dampner assesments (traffic)*

So, the reds seems to work bad..?!?!?
they have the same rebound as the yellows...with the oem compression:seems to be a daily setup...with comfort and control....but you say that they have too much rebound?
I was thinking to buy a set of reds..but after your test i'm thinking is better to wait a set of yellows, in combination with my H&Rs....


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## eggroller (May 25, 2000)

abawp said:


> Has a set of KW adjustable shocks been on the shock dyno yet?


Old question but just revisiting this thread...

KW uses Koni dampers
Stasis uses Motorsport and Challenge series use Ohlins dampers. Their Touring series uses Koni.

Correct me if I am wrong. Thanks.


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