# Let's talk TT suspension



## madmax199 (Oct 28, 2009)

I am relatively new to the community and I see a lot of frequently asked questions when it comes to the TT’s suspension and not a lot of info available and compiled in one solid thread. I will describe the basics and try to keep it simple in the first couple of posts so most can benefit from it. After that, it can get more technical for those interested.


*Part 1*

The TT comes with MacPherson strut design in the front with a 3 point lower control arm and a directly coupled stabilizer (swaybar or anti roll bar are commonly used when referring to stabilizers so I‘ll use swaybar to make things easy).
Another thing maybe worth mentioning is that the front geometry has negative steering roll radius (NSRR).

NSRR can be understood by drawing an imaginary line down through the ball joints when looking at the car from the front. The point where that imaginary line hits the ground is said to be negative if it lands outside the tire’s centerline (like in the TT). The effect of all that is to offset sudden steering pull from various situations (flat tires, torque steer etc.)

In the rear the TT come with: torsion beam axle and trailing arms for the FWD; while
the AWD cars are blessed with fully independent parallelogram multi-links.
Most of my modeling and modifications have been done on an AWD TT so I will concentrate more on that setup.

All of the above is only a description of what the TT comes with and probably would means nothing to most if there was not a more in depth explanation of the advantages and negatives of the design, so I will try my best to break it down and explain.

*Front:*



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MacPherson is popular with car manufacturers because of the lower cost of design and easy packaging but performance is also limited for various reasons.
In the TT (like most cars with MacPherson) the camber curve goes positive after a few degrees of body roll, mostly because of the arc the control arm is following. What that does to handling is that it places the loaded tire in bad spot, where only a portion of the available contact patch is actually making contact with the road thus reducing the available grip. 

The second most noticeable drawback is that this design introduces a lot of toe changes throughout the range of motion. Toe changes causes thing to be unpredictable and also mess with other design parameters like Ackerman angles or scrub radius etc (more on that 
later)

*Rear:*


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"Multi Links" is a nicer suspension design that allows full independence. One parameter can potentially be altered without having an effect on the rest. For example, dynamic camber changes does not significantly affect toe like it does in the front. There is still some degree of bump steer but more on that later also.

Since we can not go around the design, the only thing left to do is to model the suspension and work with what is available to help it perform better.

We have established that body roll causes camber and toe changes and most TT owners invest in stiffer springs, coilovers and swaybars in an attempt to reduce the amount of body roll and its negative effects (I am aware that some also spend money just for looks and we will leave that aside). 

What is body roll and how does coilovers, upgraded swaybars, stiffer bushings affect it? 

Simply put, body roll is the lean that the car have when it's taking a turn. It is a result of longitudinal and lateral load and weight transfer and the associated shift in the center of gravity. 

Coilovers and swaybars both increase the wheel rate (stiffness in lbs when measured at the wheels and not the springs). When the wheel rate increases, the resulting body roll(in degrees) present when taking a turn (at a set G load) is reduced. Reducing the body roll, help keep the tire in a more favorable spot in the camber curve and handling is improved.

Lowering the car, and the center of mass with it, has a positive effect on load transfer relative to the car’s wheelbase. However, lowering also have effect on roll center and that effect is detrimental to handling, when not done properly in relation to the available geometry.

*In general:*
Making the TT stiffer=Good
Lowering the TT= OK up to a point and BAD pass that point.

The following schematic is borrowed from forum member pyce that did some great modeling and simulation on the Mk1 front suspension a long time ago. It’ll illustrate what lowering does to camber, when the suspension is loaded in a turn with some steering angle (10 degrees). Stock is red, pink is lowered 30mm and the yellow curve is with a lowering of 60mm. You can see that lowered 60mm is better than stock up to 4 degree of roll and pass that; a stock height car would actually have an advantage with its camber curve. 




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I’m sure that this will make you wonder how much your TT really rolls when you make an aggressive turn. I would say a lot, another borrowed picture from a fellow autocrosser shows how much roll can be generated, even with a car with really stiff springs and relatively low steering angle. The TT is a front heavy car that rolls a lot and does not have the best front geometry, so lowering should be kept to a minimum or handling is seriously going to suffer, street or track.





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## madmax199 (Oct 28, 2009)

*Part 2*

In part 1, we talked about the TT’s suspension design and the effect of lowering on the camber curve.

Then, how come lowering the car and the static center of gravity with stiffer springs/coilovers is not helping weight transfer and handling? 
It is in reality, but lowering in a car with MacPherson design has a bigger, more detrimental impact on the roll center and ultimately the roll couple.

Roll center: 

It is the point that the car rotates around when cornering loads are introduced. It is a virtual point that dynamically changes but it can be measured statically.

In a MacPherson design like the TT’s front, to find the roll center you must first calculate your instant center (point in space that the suspension link rotate around). To do that, you simply need to draw a 90 degree angle at the upper mounting point of your strut axis, the point in space where that 90 degree angle meet with a straight line drawn from your lower control arm is the instant center. 

After that, finding the roll center is easy. 
First, draw a line from the center of the tire’s contact patch to the instant center, the point where that line intersect the car’s center line is your roll center (for that axle). Although it may seem complicated, it’s really easy to calculate (if I can do it, anyone can).



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It is to be noted that there is a front and rear roll center and they are fully independent of each other and determined by their respective axle geometry. I only focused on the front roll center for now, because lowering is more problematic on that end in the TT because of the geometry. 



*Roll couple*: 
It’s the distance between the roll center and the center of gravity. It is the lever arm that centrifugal forces, working on the center of gravity, uses to make the car roll in a turn. To keep things simple, the greater that distance is, the higher the car’s tendency to roll will be (keeping this distance short will make the car handle better and more responsive to steering inputs because less weight is transferred to the outside wheel during cornering). 

Look at the strut suspension schematic(top) to see the difference in roll couple between stock and lowered


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When you lower your car, you lower both the center of gravity (good) and the roll center (bad). With the TT’s front geometry the roll center drop a lot more than the center of gravity for the same drop. The result is a higher roll couple and a tendency to roll more than before even with stiffer springs and bars.

In the following schematic, you can see that having a control arm parallel to the ground bring the roll center above ground, closer to the center of gravity (creating a smaller roll couple); a slightly angled control arm(outer pivot point higher than inner one) put the roll center at the ground level. In some extreme cases static roll center can even go subterranean.



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Now that we looked into the roll center and roll couple. We can add that the roll center is mainly a dynamic point that migrates when the car is in motion. The car stiffness or ability to fight roll is highly impacted by the wheel rate (wheel rate =spring rate *(motion ratio^2)
To fully understand the wheel rate we need to have an understanding of the motion ratio.

*Motion ration*: in layman’s terms is the leverage the springs/swaybar are exerting at the wheel in regards to its respective geometry. In the TT for example the motion ratio in the front is 0.97 that is because the spring/shock is mounted almost above the ball joint.


The rear of the TT however has a motion ration 0.63 because the spring is mounted inboard of the outer pivot point on the control arm. Any spring in the back of the TT would have their effective rate at the wheel cut by that percentage. Running 1000 lbs springs in the back has the same effect as running 1000lbs X 0.63 = 630lbs springs.

All of this, only means that springs and swaybar selection, as well as ride height should be a balancing act that needs to be done in respect to the goals and purpose of the car. 

Before I make an attempt to tie everything together dynamically, there are a few things that need to be looked into (Natural frequency, Ackerman angles, bump steer and alignment) but that’s for part 3 :beer:.


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## madmax199 (Oct 28, 2009)

*Part 3*
We have looked at several basic concepts in part I and II. In long overdue part III I’m going to attack Natural Frequency, Ackerman angles, bump steer and alignment.

The TT, like most modern automobiles, has their sprung mass carried by 4 springs (see below).



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I said sprung mass because the rest of the suspension bits, braking components and wheel/tire combo below the springs are not supported by them. They are called unsprung weight, unsprung weight although seemingly insignificant plays an important role on how a car handle. To keep it simple, the lower the total unsprung weight is, the better the car will react to imperfections and follow bumps on the road, and the better it will handle (think of it as weight reduction for suspension). 

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Now that we know what the springs are carrying and not carrying, we can explore the term Natural Frequency that I’ve been mentioning. However before we get into it, I need to quickly say that the sprung weight in the TT is not evenly distributed over each axle or each spring (the TT roughly have a static overall weight distribution of 60/40 front to rear).

The *Natural Frequency* (NF) is the number of time the springs on a specific axle move up and down after a bump is encountered. Natural frequency is calculated over a period of time (1 second) and that’s why it’s expressed in Hertz (Hz). So, say you’re going down the road to see your girl and hit an expansion joint, your front axle springs will oscillate X times in a second and the rear axle ones Y times. You may be asking yourself why Natural Frequency is important then. Well, simply because it is the main factor in spring selection (not the weight of the car or the distribution of that weight. The human body feels comfortable with a Natural Frequency of 1 Hz or 1 up/down cycle per second. When choosing spring rates for whatever the purpose of the car, you need to decide what NF it will operate best. Regular commuter cars usually come sprung in the 1-1.5 Hz range and it’s perfect for comfort. Sportier cars, depending on the manufacturer, can have a NF of 1.5-2 Hz (I never cared to calculate the NF of the TT on OEM springs so I don’t know what it is). It is not uncommon for racecars to have over 3 Hz of Natural Frequency. In my TT that’s built for autocross but still driven daily, the NF is 2.8 HZ/3 Hz front to back. The next question, if anyone is still following, is why the higher NF in the back if the weight distribution is 60/40? The answer is balance. Ideally when taking a turn, you want the car to settle as quickly as possible so you can have maximum grip and be able to apply maximum throttle. If the NF is offset with the rear reacting faster than the front, you could actually optimize for a certain speed and have both front and rear settle at the same time even if the front went into motion before the back.

The *Ackerman angles* are part of the suspension geometry and determined by the steering linkages in relation to the axles. The reason for such angles is to allow the wheels on the steering axle to follow the same path when turning without any scrub. Let’s say the car is making a left hand turn, the passenger side wheel has to follow a greater radius and the result without some Ackerman angle designed in the geometry is scrubbing. All cars now have some Ackerman angles helping them but you could have “More Ackerman” “True Ackerman” and “Less Ackerman”. 

Scrub free radius followed by the weels with some Ackerman Angle

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The TT/R32 comes with “True Ackerman” angle, meaning that two lines drawn from the spindles steering arms intersect in the center of the rear axle. That’s OK but some real sports cars comes with “Less Ackerman angle” and that gives the car a very sharp response to steering inputs (get a ride in a Miata and you’ll understand what Less Ackerman does to a car’s behavior). The Ackerman angles are not adjustable in the TT but I discussed the subject because it is often ignored when talking suspension. In my car, I have made changes with my custom ball joint plates that altered the Ackerman angles in my car so it's not a theoretical concept that's never modified in real life.

"True Ackerman" geometry

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Before we get into the alignment, the last thing we need to look at is *Bump Steer*. Bump steer is when your wheel/tire steers as result bump or compression without any steering input. This “self steering” condition is not desirable as it upsets the car while cornering. As far as geometry is concerned, in the steering axle of a car with a single control arm like the TT, the goal is to keep the outer control arm ball joint mounting point and tie rod end outer mounting point traveling the same arc. The engineers did a good job in the TT’s front suspension; the arc followed by the tie rods and control arms are congruent, so they stay parallel with motion and there is very limited bump steer at stock height. However, when lowered more than 1”, the arcs of the control arms and tie rods diverge, creating bump steer.

This is what tie rod/control arm look like fully compressed in the TT(parallel still at the top of their arc)

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We are blessed with bolt on ball joints in this platform, which means that custom longer ball joints can be easily made to bolt up and fix the geometry even if lowered heavily. The catch though is that the tie rod ends would need to be modified as well so heavy bump steer would not be introduced. I don’t understand why there isn’t a roll center correction kit available for the platform because it’s darn easy to make and allow the car to be lowered a lot without messing out the handling (I haven’t done one for my car because my racing class restrict tie rod modification. I don’t want to deal with bump steer so I just don’t go too low in the front.)


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## madmax199 (Oct 28, 2009)

Part 4 (reserved)


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## 20v master (May 7, 2009)

Some wording semantics I could argue in there but then I'd be more like an annoying engineering professor.  I always found Ackerman angles interesting. You know your wheel rates since I've seen you post them in another thread, and you know your weight distribution, since I've asked you that before. So come out and give us your understeer gradient as well (hopefully we'll see that in a reserved post). I'd like to see that compared to the US gradient of a stock car. Thanks and staying tuned.


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## madmax199 (Oct 28, 2009)

20v master said:


> Some wording semantics I could argue in there but then I'd be more like an annoying engineering professor.  I always found Ackerman angles interesting. You know your wheel rates since I've seen you post them in another thread, and you know your weight distribution, since I've asked you that before. So come out and give us your understeer gradient as well (hopefully we'll see that in a reserved post). I'd like to see that compared to the US gradient of a stock car. Thanks and staying tuned.


I knew you would've picked up on wording semantics, 
I am reading the part1 again and I can see some problems with specifics like load transfer vs weight transfer and center of gravity vs center of mass as they are not the same. However it is hard to give basic definitions that make sense to everyone without kind of blending together some things. I was hoping that you would give me a chance to get everyone up to speed before we get to the fun stuff.

I assure you that part 3 and 4 is gonna tackle what you are looking for and we will have a nice discussion going.


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## DCMS371 (Jul 24, 2008)

This is an awesome thread. I can't wait to see what your final recommendations are going to be ...


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## Vdub 2.0 (Jan 8, 2008)

:thumbup:


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## omerkm1 (Feb 23, 2010)

another great post Max. thanks. :thumbup:


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## l88m22vette (Mar 2, 2006)

Excellent, linked to FAQ


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## omerkm1 (Feb 23, 2010)

l88m22vette said:


> Excellent, linked to FAQ



:beer:


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## Doooglasss (Aug 28, 2009)

I'm all ears opcorn: & :beer:


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## madmax199 (Oct 28, 2009)

part2 posted:beer:


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## 20v master (May 7, 2009)

Now you're going to start losing people. :laugh:


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## Late__Apex (Dec 2, 2007)

Anyone with access to suspension geometry software care to calculate the roll centers of the TT?


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## madmax199 (Oct 28, 2009)

20v master said:


> Now you're going to start losing people. :laugh:


Hopefully not until part 4, when we look at the whole picture for the TT dynamically.


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## madmax199 (Oct 28, 2009)

Late__Apex said:


> Anyone with access to suspension geometry software care to calculate the roll centers of the TT?


I did and do so every time I make changes to the ride height. The problem with posting roll center height and center of gravity height is that it varies from car to car depending on the height. 

You should just calculate yours and if you don't have access to your center of gravity(use crankshaft height as an estimation) so you can get your roll couple(more important)

I don't mind posting my roll center and ride height but I don't want someone to think that theirs is gonna be the same.


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## omerkm1 (Feb 23, 2010)

madmax199 said:


> I did and do so every time I make changes to the ride height. The problem with posting roll center height and center of gravity height is that it varies from car to car depending on the height.
> 
> You should just calculate yours and if you don't have access to your center of gravity(use crankshaft height as an estimation) so you can get your roll couple(more important)
> 
> I don't mind posting my roll center and ride height but I don't want someone to think that theirs is gonna be the same.



Max - What height are you running your RSS coilovers at? I am blown away with how stiff they are and its great having everything pre set, nothing for me to screw up. Also, you are running different springs but who revalved the struts?


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## madmax199 (Oct 28, 2009)

omerkm1 said:


> Max - What height are you running your RSS coilovers at? I am blown away with how stiff they are and its great having everything pre set, nothing for me to screw up. Also, you are running different springs but who revalved the struts?


Yes the rss are very stiffly sprung and valved. I was shocked by how much compression H&R put in them. when we had them on the dyno, they looked like they could've been raced without doing anything to them but the compression curve had me worried that they would only work really well on silky smooth surfaces. 

The revalve and dyno was done by a friend of mine that is the shock engineer for a big race team. Bilstein California can rebuild and revalve them also(if you ever revalve them, remove a little compression and add about 15-20% rebound and you will be in business)

As far as ride height, measuring at the fender, the fronts are a little under 26" and the rear measure at about 24.5"

The measurement is a little different at each fender because the car is corner balanced and my tire size is 225/45 X 17 so you can have a rough idea.


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## omerkm1 (Feb 23, 2010)

madmax199 said:


> Yes the rss are very stiffly sprung and valved. I was shocked by how much compression H&R put in them. when we had them on the dyno, they looked like they could've been raced without doing anything to them but the compression curve had me worried that they would only work really well on silky smooth surfaces.
> 
> The revalve and dyno was done by a friend of mine that is the shock engineer for a big race team. Bilstein California can rebuild and revalve them also(if you ever revalve them, remove a little compression and add about 15-20% rebound and you will be in business)
> 
> ...



:beer:


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## taverncustoms (Feb 18, 2011)

nice thread..... so what do you sugest.opcorn:


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## madmax199 (Oct 28, 2009)

taverncustoms said:


> nice thread..... so what do you sugest.opcorn:


In terms of what (ride height, coilovers, swaybars, alignment) ?


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## mbaron (Aug 21, 2008)

taverncustoms said:


> nice thread..... so what do you sugest.opcorn:


You have to be a lot more specific than that. 

What are your goals with the car? 

Do you care about handling or do you just want low? 

How firm a ride can you handle? 

Do you need adjust-ability?


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## taverncustoms (Feb 18, 2011)

mbaron said:


> You have to be a lot more specific than that.
> 
> What are your goals with the car?
> 
> ...


BEST HANDLING IF YOU PLEASE. IF I WANTED COMFORT I WOULD HAVE A CADILIAC
not making a lowrider. but a lower stance should help with roll

I read somewhere that stiffer rear and softer front springs help eliminate understeer. and that you want the softest spring possible with the biggest sway bar possible for best handiling
handling. is that just BS?


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## omerkm1 (Feb 23, 2010)

taverncustoms said:


> BEST HANDLING IF YOU PLEASE. IF I WANTED COMFORT I WOULD HAVE A CADILIAC
> not making a lowrider. but a lower stance should help with roll
> 
> I read somewhere that stiffer rear and softer front springs help eliminate understeer. and that you want the softest spring possible with the biggest sway bar possible for best handiling
> handling. is that just BS?



There are hundreds of threads about this suspension setup and that suspension setup. Best thing to do is figure out what you want the car to do and how much you have to spend. If you figure out those 2 things then it will make choosing parts much easier. :thumbup:


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## madmax199 (Oct 28, 2009)

taverncustoms said:


> BEST HANDLING IF YOU PLEASE. IF I WANTED COMFORT I WOULD HAVE A CADILIAC
> not making a lowrider. *but a lower stance should help with roll*


Lower stance hurts body roll badly (in the front) if lowered too much. 
You have two choices:
1) keep the lowering to a minimum(an inch or so). 
2) Correct the geometry by raising the roll center back up, to account for the lowering. 

The second option can be achieved by adapting taller ball joints to the front control arm(pretty easy to do since we are lucky to have bolt on ball joints). I haven't done that to my personal car because taller balljoints are illegal in SCCA street prepared. If anyone were to adapt taller BJ you'd also need to lower the tie rod ends the same amount for some other reason I don't want to get into now but it's needed.



taverncustoms said:


> I read somewhere that stiffer rear and softer front springs help eliminate understeer. and that you want the softest spring possible with the biggest sway bar possible for best handiling
> handling. is that just BS?


Mostly BS, yes the TT need stiffer springs in the back to handle correctly because of the motion ratio(0.98 front/0.63 rear, so beware of any coilovers in the market designed with stiffer front springs because they can't physically work right).

Anyone telling you that you want the stiffest bar and softest spring for handling does not know what they are talking about. You want your spring to be your main way of controlling body roll, the bars should be be for trimming/fine tuning the balance of the car. 
*The less bar the better*, because amongst other things, you remove grip and independance in the set up. The reason most well set up cars, including me, still use swaybars is because they offer a quick and easy way to adjust balance. Without them you'd need uber stiff springs that can become problematic on bumpy surfaces because of the high natural frequencies that comes with it.

I personally run a modified "softer" stock front bar with a stock rear swaybar. I ran sans swaybar in the back for a while but brought it back to the equation because I wanted a little more rear wheel rate. Altough I have 1150Lbs rear springs, the motion ratio in the back bring my wheeel rate down quite a bit. I am not a fan of the rear swaybar at all because it promotes tripod but there is not much I can do until I run a true Coilover set up in the back(in the works).


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## taverncustoms (Feb 18, 2011)

I found this on a F1 site has some good info.


•Springs: A spring that’s not stiff enough under cornering doesn’t properly counteract the car’s tendency to roll, moving its centre of gravity outwards and quickly overwhelming the outer tyre’s ability to keep a grip on the road. A spring that’s too stiff slows the transfer of load from the inner to the outer tyre too much; as a result, the outer tyre isn’t being loaded enough to achieve its potential before the corner is over. However, the spring rate that’s just right for one corner on the track may be wrong for the next one, because of the corners different shape and speed. To further complicate matters, the difference front to rear must be considered as well. If the spring rate at the rear is just right, both toostiff or too-soft at the front produces understeer. If the front rate was just right, both too-stiff or too-soft at the rear produces oversteer. The driver and his engineer need to find a compromise over the many and varied corners of the track; this compromise may involve surrendering some grip from one end of the car to get the desired balance. At circuits with a wide variation of corners, variable rate springing may be used to give a relatively soft spring at low speeds but a stiffer one at high speeds.

•Dampers: Dampers don’t determine a car’s grip as much as they determine how much of the grip the driver can access. The dampers offer a very effective way for drivers to fine-tune the car’s handling in the limited time of a practice session. The damper is adjustable in the bump phase of its progression (as it absorbs the initial bump) and in the rebound phase. These adjustments can be made in two ranges – low speed and high – to give four-way adjustment. The damper is also adjustable within the overall range of frequencies in which it works, although this involves fitting different internal valves – not normally something done during practice. A driver might soften the bump rate if the car’s trajectory is being affected by bumps in the braking or cornering zones or if he wants to use more kerb without being thrown off line. Softening the damper’s bump rate allows the spring to smother more of the bump’s effect. A driver may increase the damper’s rebound setting in order to keep the nose of the car down after he has finished braking to help him get the car turned into the corner. In addition dampers include “blow-off valves”. These valves enable the damper to ignore any out-of-range inputs so that, for example, a severe kerb can go undamped beyond a certain range and so not compromise the settings needed on the rest of the track.
•Arms: The linkage formed by the suspension arms and how they interact front to rear have a direct bearing on the overall handling characteristics of the car. The geometry of the wishbone linkages determine the roll centre of the car. The roll centre is an imaginary, but accurately defined, point on the centre-line of the car around which the car rolls on its suspension. The roll centre can be high off the ground, low, or even underneath the ground (it’s only imaginary, remember). A line connecting the rear suspension roll centre with that of the front is called the roll axis. If the axis runs nose-down, the car tends to oversteer. If the axis runs nose-up, the car tends to understeer. These linkages are intrinsic to the car’s design and can’t be changed during a race weekend, but some adjustment can be made to the car’s ride height (the height above the ground of the car’s underside) via the suspension’s pushrod. The closer to the ground, the more grip but the less the car can tolerate bumps and kerbs. The camber of the wheels can be altered by adjusting the wishbones so that the highly-loaded outer wheel becomes upright under cornering and uses more of the tyre’s width rather than just the outer edge. (Here, camber refers to when the wheels aren’t perfectly upright, but run at an angle to the road surface, usually with the bottom pointing in slightly.) The downside of altering the camber is that it makes the car less good under braking.
•Roll bars: Roll bars have a big effect on the car’s handling, particularly in the first part of a corner as the driver turns in. The bar’s primary function is to keep roll under control, but the way it does this also results in cornering load being transferred from the inner tyre to the alreadyloaded outer tyre. If the spring rates aren’t too stiff, this detracts from ultimate grip. Taking grip away from the front or the rear by increasing the stiffness of the roll bar gives the driver another tool in adjusting the car’s handling balance.


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## madmax199 (Oct 28, 2009)

taverncustoms said:


> The bar’s primary function is to keep roll under control, but the way it does this also results in cornering load being transferred from the inner tyre to the already loaded outer tyre. If the spring rates aren’t too stiff, this detracts from ultimate grip. Taking grip away from the front or the rear by increasing the stiffness of the roll bar gives the driver another tool in adjusting the car’s handling balance.


We can not honestly be using F1 machines as references for mass production utility cars. The physics remain the same but the designs are so different that we may as well be comparing freight trains to bicycles.

The section I quoted, is to me the only relevant part to our our discussion. It reinforces my view about the role and effects of swaybars to any car's handling. They really are, on performance oriented cars, bandaids masking a lack of spring rate. Used in moderation, since they ultimately remove grip, can be used as a tool to fine tune the balance.


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## taverncustoms (Feb 18, 2011)

madmax199 said:


> We can not honestly be using F1 machines as references for mass production utility cars. The physics remain the same but the designs are so different that we may as well be comparing freight trains to bicycles.
> 
> The section I quoted, is to me the only relevant part to our our discussion. It reinforces my view about the role and effects of swaybars to any car's handling. They really are, on performance oriented cars, bandaids masking a lack of spring rate. Used in moderation, since they ultimately remove grip, can be used as a tool to fine tune the balance.


as far as i can tell its saying the same thing


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## taverncustoms (Feb 18, 2011)

*1) keep the lowering to a minimum(an inch or so). *
im thinking 5. to 1 in drop

*2) Correct the geometry by raising the roll center back up, to account for the lowering. *

will this be nedded for a .5-1" drop

*Mostly BS, yes the TT need stiffer springs in the back to handle correctly because of the motion ratio(0.98 front/0.63 rear, so beware of any coilovers in the market designed with stiffer front springs because they can't physically work right).*

so for best handling your recomend _________ springs? "i dislike coil overs"

*I personally run a modified "softer" stock front bar with a stock rear swaybar.*

could the same dynamic be achived by using a heaver rear swaybar and stock front?


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## 20v master (May 7, 2009)

Geometry isn't horrible with a 1/2" to 1" drop, but the dynamic camber does suffer slightly at the limits compared to stock height. No off the shelf springs (H&R, Neuspeed, etc) will give "the best handling." This means you'd need custom spring rates, not hard to do, just beyond what most people are going to do. Weight of the swaybar has nothing to do with it, it's the length of the bar "arms" that he is referring to. He's already explained why he uses stock bars and what he uses them for, if you didn't understand his comments I suggest you read them again. Big bars limit roll greatly but remove some of the independence of the suspension sides, so if you raise a wheel, you've lost 1/4 of your grip. As he already said, springs should control most of the roll, not the bars.


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## madmax199 (Oct 28, 2009)

Yup, 20V said it all...

This is what a stiff rear bar does to a car from corner entry to mid corner(in my old evo in first pic and a TT in the second pic)
There is two big problems:

1) Once that rear wheel is off the ground all the weight carried on that corner get instantly tranfered to the already strugling opposite front(creating understeer)

2) On an AWD car, like the TT, you have to wait for that wheel to get back on the ground before you can get apply any decent throttle( if you do so before the wheel is down the car plows out of line)



Uploaded with ImageShack.us



Uploaded with ImageShack.us


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## omerkm1 (Feb 23, 2010)

taverncustoms said:


> *1) keep the lowering to a minimum(an inch or so). *
> im thinking 5. to 1 in drop
> 
> *2) Correct the geometry by raising the roll center back up, to account for the lowering. *
> ...



You might like the H&R RSS Coils, very little drop and probably the stiffest springs you can buy. Also I found that the HPA coils have very little drop but the springs arent what you are looking for. 

In saying that you dont like coilovers, is it because you dont want to mess with settings? The RSS coils are great for that because they are pretty much a full on track set up with zero adjustment. I run mine basically as high as they will go with a slight front to back rake. This is so much better than the H&R springs that were on the car. 

Another idea that stays away from coilovers is a set of heavy duty bilstein shocks paired with GC r32(r32 and TT are the same) springs with whatever spring rate you want. Bilstein can re-valve the shocks to the spring rates of the spring. Max can verify if I am full of crap or not. :laugh:


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## Doooglasss (Aug 28, 2009)

My first set of coilovers was a pair of HPA SHS's and they are a great comfort coilover but not performance oriented at all. They are repackaged KWv1's but softer IIRC.

Just an FYI/shamless plug: I might have my set of RSS's up for sale soon- as well as many other parts.


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## 20v master (May 7, 2009)

omerkm1 said:


> Another idea that stays away from coilovers is a set of heavy duty bilstein shocks paired with GC r32(r32 and TT are the same) springs with whatever spring rate you want.


Ground Controls only work with Koni or stock style shocks, not Bilstein's. And I know they make them, but they don't even list TT/R32's on their site.


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## omerkm1 (Feb 23, 2010)

20v master said:


> Ground Controls only work with Koni or stock style shocks, not Bilstein's. And I know they make them, but they don't even list TT/R32's on their site.


:thumbup: You are correct. 

Max is running GC springs on the RSS coilover bodies if I remember reading correctly. But he also seems to have a machine shop at his disposal. :laugh:


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## rburt (Oct 25, 2007)

*thanx*

i need to keep my front end on ground, spirited acceleration in 1st and especially 2nd, is raising my front end to where the wheels slip, as my tires get more worn it happens even more... suggestions welcome


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## omerkm1 (Feb 23, 2010)

rburt said:


> i need to keep my front end on ground, spirited acceleration in 1st and especially 2nd, is raising my front end to where the wheels slip, as my tires get more worn it happens even more... suggestions welcome



are you fwd or quattro? 

if quattro, haldex controller shifts the power to the rear sooner. if fwd, then you can go with some lowering springs or HPA also makes a SHS coilover set with optional drag shocks.


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## 20v master (May 7, 2009)

rburt said:


> i need to keep my front end on ground, spirited acceleration in 1st and especially 2nd, is raising my front end to where the wheels slip, as my tires get more worn it happens even more... suggestions welcome


In what type of driving? Power level? Tire brand/model and size?


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## rburt (Oct 25, 2007)

*thanx km1*

my setup is blue haldex, new koni FSDs, Eibach springs, all season 18" tires new at Christmas. 

i think the stage1 motor and trany mounts really lift it. GIAC chip with K/N filter only. 

wish it would stay on the ground


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## l88m22vette (Mar 2, 2006)

Can anyone guide me to a smaller front sway? Car source, part number?


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## madmax199 (Oct 28, 2009)

rburt said:


> i need to keep my front end on ground, spirited acceleration in 1st and especially 2nd, is raising my front end to where the wheels slip, as my tires get more worn it happens even more... suggestions welcome


Amount of squat is determined by your rear wheel rate and to a certain degree your front shock rebound. 

To reduce that squat you'd need to increase your rear spring rate considerably but the shock yould need to be valved accordingly .


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## madmax199 (Oct 28, 2009)

l88m22vette said:


> Can anyone guide me to a smaller front sway? Car source, part number?


I don't think another swaybar is going to fit in the front of the TT. 

I have modified a stock bar to make it softer in rate in my car. It should be pretty easy to replicate and the link on the bottom of my sig should have pictures of the modifications.


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## 20v master (May 7, 2009)

rburt said:


> my setup is blue haldex, new koni FSDs, Eibach springs, all season 18" tires new at Christmas.
> 
> i think the stage1 motor and trany mounts really lift it. GIAC chip with K/N filter only.
> 
> wish it would stay on the ground


Are you sure the Haldex is working? You're getting tire spin in a straight line with just a stock turbo and no exhuast work?



l88m22vette said:


> Can anyone guide me to a smaller front sway? Car source, part number?


I don't think anyone makes one, you'd have to go the max route and move the mounting point of the end link towards the rotational axis (where the bushings are) to give the bar less leverage. This is easily done by welding tabs with bolt holes to the end of the bar (and perhaps drilling through the bar to allow the bolt to pass through, meaning you'd need a U bracket of sorts to weld to the bar).


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## rastta (Feb 22, 1999)

l88m22vette said:


> Can anyone guide me to a smaller front sway? Car source, part number?


If you can find a MK1 pre-recall - the front bar was 19mm instead of 20mm. Good luck with that!


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## l88m22vette (Mar 2, 2006)

20v master said:


> I don't think anyone makes one, you'd have to go the max route and move the mounting point of the end link towards the rotational axis (where the bushings are) to give the bar less leverage. This is easily done by welding tabs with bolt holes to the end of the bar (and perhaps drilling through the bar to allow the bolt to pass through, meaning you'd need a U bracket of sorts to weld to the bar).


How about using VW's part bin? The front is 95% mk4 so I bet another a4 chassis front sway would work...anyone know of a size listing?


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## 20v master (May 7, 2009)

l88m22vette said:


> How about using VW's part bin? The front is 95% mk4 so I bet another a4 chassis front sway would work...anyone know of a size listing?


# Golf: 21mm/18mm (front/rear)
# Jetta: 23mm/18mm (front/rear)
# GTI and most factory sport suspensions: 23mm/21mm (front/rear)


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## taverncustoms (Feb 18, 2011)

ok so i guess the only remaining questions would be: what spring rates are you running, and would you change the rate if you were to order a new set? 

after watching your video i realy like what you have done and would like to see your car in a high speed turn 80mph + i dont AutoX "yet" but i do a lot of "private" road mountan driving and i find most of the time i do about 55-70mph "limited by understear" in the turns. i have been abble to step the rear out but thats sketchy


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## taverncustoms (Feb 18, 2011)

to bad the bose suspenchion is still a dream.
http://www.youtube.com/watch?v=eSi6J-QK1lw&feature=related


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## madmax199 (Oct 28, 2009)

taverncustoms said:


> ok so i guess the only remaining questions would be: what spring rates are you running, and would you change the rate if you were to order a new set?
> 
> after watching your video i realy like what you have done and would like to see your car in a high speed turn 80mph + i dont AutoX "yet" but i do a lot of "private" road mountan driving and i find most of the time i do about 55-70mph "limited by understear" in the turns. i have been abble to step the rear out but that's sketchy


Right now, I run 685lbs springs in the front and 1150lbs springs in the back. The coilovers are re-valved H&R RSS.

I have a set of 1250lbs springs that is ready to go in the back for next racing season and they will allow me to reduce the rate of the rear stock swaybar(I drilled extra holes in it to make it adjustable) while increasing the wheel rate .

Ideally, for the weight of the TT and the motion ratios, I would run 750/1300 springs front to back but the high natural frequency wouldn't be too appropriate for street duties.

I have been toying with the idea of a true coil over setup in the back with twin springs on the shock and the stock location. That way such high rear spring rates could be avoided because the motion ratio would be much closer to the magic 1(because of springs over the shocks).


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## taverncustoms (Feb 18, 2011)

madmax199 said:


> Right now, I run 685lbs springs in the front and 1150lbs springs in the back. The coilovers are re-valved H&R RSS.
> 
> I have a set of 1250lbs springs that is ready to go in the back for next racing season and they will allow me to reduce the rate of the rear stock swaybar(I drilled extra holes in it to make it adjustable) while increasing the wheel rate .
> 
> ...


cool so you think 750/1300 would cause the car to bounce on common road conditions or be uncofortable? and what about that vid of high speed, any chance you could get one up??


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## Doooglasss (Aug 28, 2009)

I was running H&R RSS's w/ H&R sways set to stiff at the time. This setup uses the same 685/1150 that max's does. While driving on I-95 north out of NY at about 90mph I hit a patch of rolling bumps in the road and it was the scariest feeling I've ever had on a highway. Slowed me down A LOT. After loosening up the bars & raising the car up I was able to maintain a safe street ride, however, I never got a chance to go over that patch of road again.

I might be wrong, but from that experience I would say that any high spring rate is going to sacrifice ride quality and potentially safety on any road surface that isn't smooth. The suspension simply stops absorbing the difference in road quality and the tire feels as if it's skipping over the ground.

I've also driven Max's car and I felt much safer in it. I believe he pointed out that he re-valved the dampers to handle less than optimal road conditions.


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## madmax199 (Oct 28, 2009)

taverncustoms said:


> cool so you think 750/1300 would cause the car to bounce on common road conditions or be uncofortable? and what about that vid of high speed, any chance you could get one up??


Like I said, it would be my ideal spring rate for the TT's weight. However, I would only use something like that on a dedicated track car that see limited street use. It would not be bouncy per say, if the shock are valved properly, but would be unbearable on real life pot holes and road junctions.

I don't think a video of the car taking an 80+ mph turn is going to happen for me or anyone responsible. The speed limit, around me in NY, is 55 mph on the highway. I don't know of many "real turns" that are taken at that speed even on most tracks beside sweepers(not real turns). Tight slow turns are always more problematic and the real test of handling.

This a crappy video of the car on a full run so you can see the overall behavior, it is to be noted that this was taken with no rear swaybar on the car. There is still plenty of rotation with a nice on throttle slide at the 0:27 mark. I hope this is enough. :wave:

http://www.youtube.com/watch?v=uv-wdB460VY


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## rastta (Feb 22, 1999)

l88m22vette said:


> How about using VW's part bin? The front is 95% mk4 so I bet another a4 chassis front sway would work...anyone know of a size listing?


With the exception of the R32 (and maybe some SEAT's etc) all other MKIV's use a different style sway bar which has U shaped ends that connect with links directly to the LCA's and not to the front struts like the TT. They aren't going to work.


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## 20v master (May 7, 2009)

[email protected] said:


> With the exception of the R32 (and maybe some SEAT's etc) all other MKIV's use a different style sway bar which has U shaped ends that connect with links directly to the LCA's and not to the front struts like the TT. They aren't going to work.


They could easily be made to work with some adjustable links though. But its silly either way. Remove the front sway if you want less understeer.


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## rastta (Feb 22, 1999)

20v master said:


> They could easily be made to work with some adjustable links though. But its silly either way. Remove the front sway if you want less understeer.


I guess - but since the bar isn't designed to be used in that manner - you would have no idea what the rate of the bar would be in terms of stiffness. I guess you could calculate it - but as you said pretty stupid overall.

If you remove your bar - you'll need some pretty stiff springs to compensate - even if you want less understeer.


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## madmax199 (Oct 28, 2009)

[email protected] said:


> I guess - but since the bar isn't designed to be used in that manner - you would have no idea what the rate of the bar would be in terms of stiffness. I guess you could calculate it - but as you said pretty stupid overall.
> 
> If you remove your bar - you'll need some pretty stiff springs to compensate - even if you want less understeer.


You are right Joe. Some pretty stiff springs would be needed up front to keep the car flat(limited body roll in a turn) if the bar was deleted. 

As usual, if anything is to be tried I have done it. I ran without the front bar for a while and even tested it back to back at the track to see if the clock would aprove. Steady state understeer was greatly improved(sweepers) as well as mid corner to exit behavior. However, transitions greatly suffered(lack of front wheel rate) and we also noticed a reduction in turn in sharpness. I was faster without the swaybar(not by much) and my co-driver hated it and was slower that way.

I think that 700+ lbs spring woluld be needed to make the TT work "sans front swaybar". Maybe I'm going to try it and not tell my co-driver :laugh: to see what happens because personally I can deal with the numb steering( I have an SCCA EP Saturn SC1 on bias-ply cantilevers that make any steering feel sharp).


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## 20v master (May 7, 2009)

[email protected] said:


> I guess - but since the bar isn't designed to be used in that manner - you would have no idea what the rate of the bar would be in terms of stiffness. I guess you could calculate it - but as you said pretty stupid overall.
> 
> If you remove your bar - you'll need some pretty stiff springs to compensate - even if you want less understeer.


Stiffness is easily calculated. Exact stiffness is a guesstimate since you can't account for the curvature of the bars without some serious computational power/programming. Yes, you wouldn't want to remove the stock bar on stock springs, and you'd want a hefty spring rate ideally. With a FWD LSD in my GTI, removing the OEM sway did improve my lap times on a small course, though this may not be the case with the AWD TT's.


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## rastta (Feb 22, 1999)

20v master said:


> Stiffness is easily calculated. Exact stiffness is a guesstimate since you can't account for the curvature of the bars without some serious computational power/programming.


So - stiffness isn't easily calculated - because of the bend in the bar as well as the length of the attachment points - which was my point originally. Makes sense to me to try :screwy:



> Yes, you wouldn't want to remove the stock bar on stock springs, and you'd want a hefty spring rate ideally. With a FWD LSD in my GTI, removing the OEM sway did improve my lap times on a small course, though this may not be the case with the AWD TT's.


Suspension set for AutoX is so much different from the setting it up for the street as well as setup for cars that see street use and track use. Assuming that everyone has the skills to deal with abrupt changes in a cars behavior is also a recipe for disaster. What size rubber are you running in AutoX?


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## 20v master (May 7, 2009)

[email protected] said:


> So - stiffness isn't easily calculated - because of the bend in the bar as well as the length of the attachment points - which was my point originally. Makes sense to me to try :screwy:
> 
> 
> 
> Suspension set for AutoX is so much different from the setting it up for the street as well as setup for cars that see street use and track use. Assuming that everyone has the skills to deal with abrupt changes in a cars behavior is also a recipe for disaster. What size rubber are you running in AutoX?


Sway bar stiffness formulas are easily found online and able to be understood even by simpletons. There are several assumption that go into that layman's formula. Like I said, finding the exact stiffness would require some finite element analysis and approriate computations, which the average enthusiast isn't going to do. Try calculating the stiffness of a progressive rate spring. The point is that neither of those tasks are going to be done by 99% of people out there. You are correct, the setup for different uses is up to the user. However, implying that someone can't handle abrupt changes in a car's behavior also assumes they shouldn't be driving much less modifying their car for performance. I'm not sure where your attitude is coming from. BTW, I never said I auto-x'ed. I said small course. To me, that implies banking and not being in a parking lot with cones.


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## madmax199 (Oct 28, 2009)

[email protected] said:


> So - stiffness isn't easily calculated - because of the bend in the bar as well as the length of the attachment points - which was my point originally. Makes sense to me to try :screwy:
> 
> 
> 
> Suspension set for AutoX is so much different from the setting it up for the street as well as setup for cars that see street use and track use. Assuming that everyone has the skills to deal with abrupt changes in a cars behavior is also a recipe for disaster. What size rubber are you running in AutoX?


Joe and 20V, I don't see where calculating swaybar stiffness is a problem. I am not sure if I sent my suspension calculator to both of you, but it has a section for calculating swaybar rate. The bends are not a problem because you measure from the links mounting points, to where the arms bend into the horizontal section of the bar. I know it's not for everyone but it's not rocket science.

Joe, I think this is the second time I see you say that setting a car for autox and the road course is different. In my experiences there no difference at all, besides that you maybe dial in/dial out a little rotation.

I have an scca EP car and scca designed their rules so the cars can compete, both in road racing and Solo. Most of the guys,including me, use these car for double duty and what works in one, is 99% of the time, the hot ticket for the other.

The same goes for the streets, an scca competition, Street prepared car is suppose to be livable in the streets while offering great handling. Most people get the idea that a car that can handle, is uncomfortable for the street. If the shock valving is appropriately matched to the springs, it will be fine for most and probably more comfy than most "off the shelf coilovers" with half the spring rate.

BTW guys, I like the fact that we have discussion going. I think that the whole community will benefit from it and it was the reason I started this thread:thumbup::thumbup::thumbup:.


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## 20v master (May 7, 2009)

madmax199 said:


> Joe and 20V, I don't see where calculating swaybar stiffness is a problem.
> 
> Most people get the idea that a car that can handle, is uncomfortable for the street. If the shock valving is appropriately matched to the springs, it will be fine for most and probably more comfy than most "off the shelf coilovers" with half the spring rate.
> 
> BTW guys, I like the fact.


It's not hard, but Joe thinks because the G/J/NB version has a bend on the end and the TT/R32 version doesn't that the stiffness calculations would be totally different, which they aren't. And I've been telling people the part about matching spring to shock for years, and usually just get a confused look in return. :laugh:


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## rastta (Feb 22, 1999)

20v master said:


> It's not hard, but Joe thinks because the G/J/NB version has a bend on the end and the TT/R32 version doesn't that the stiffness calculations would be totally different, which they aren't. And I've been telling people the part about matching spring to shock for years, and usually just get a confused look in return. :laugh:


Not because of the bend - because it attaches in a completely different manner and takes forces from below rather than above as the TT bar does. Looking at the sway bar calculator - it would appear that the length of the bend would factor into the calculations. I'm not saying it's impossible - but that there are more factors at play making it difficult to just compare bar diameters - which was the point of the OP's post - looking at smaller diameter front bars for his TT.


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## 20v master (May 7, 2009)

[email protected] said:


> Not because of the bend - because it attaches in a completely different manner and takes forces from below rather than above as the TT bar does.


I own and am familiar with two of each style. It would work the exact same with the approriate end link.


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## rastta (Feb 22, 1999)

20v master said:


> I own and am familiar with two of each style. It would work the exact same with the approriate end link.


So do us all a favor - put a MKIV bar on the TT and report the results - stiffer or softer. Include pics as well. Then follow up with all the calculations which show why it is stiffer or softer. IIRC - the stock MKIV GTI bar is 22mm in diameter. Since the stock TT bar is 20 mm and you can get a 19mm bar - and the original OP's asking about a smaller or less stiff bar it makes sense to spend the time to do this.

You can make anything work............however - you continue to forget the reason for the whole discussion in the first place.


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## 20v master (May 7, 2009)

[email protected] said:


> So do us all a favor - put a MKIV bar on the TT and report the results - stiffer or softer. Include pics as well. Then follow up with all the calculations which show why it is stiffer or softer. IIRC - the stock MKIV GTI bar is 22mm in diameter. Since the stock TT bar is 20 mm and you can get a 19mm bar - and the original OP's asking about a smaller or less stiff bar it makes sense tway to o spend the time to do this.
> 
> You can make anything work............however - you continue to forget the reason for the whole discussion in the first place.


A favor is something I do for courteous people. You are just being argumentative for the sake of wanting to be right. The cars share the same subframe and same dimension control arms. The front tracks are the same. Even the KW coils on my GTI have the mount for the TT style bar and link. I know the reason for the original question, and I posted an explanation of how to achieve it with some relatively simple fabrication. Again, you just want to argue that a hooped sway is impossible to make work in a TT. Yes there isn't a smaller OEM bar. Yes the question was is there a way to decrease the stock front sway rate. Yes you are just arguing to argue. No I don't have time or the desire to do the work to prove you wrong. Sorry this went on a tangent max.


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## madmax199 (Oct 28, 2009)

No tangent, it's all part of having a good discussion. 

Personally, altough I haven't seen an Mk4 bar, I don't think it's worth the trouble to try a thicker bar on the car if the goal is to reduce the rate. 

Unless the MK4 arms have considerably longer arms vs the TT bar, it's going to be stiffer regardless of mounting points.

Can any of you guys post a pic of a vw bar mounted?
I'd be willing to make another mk4 bar work on the TT, but it would have to be thinner in diameter to warrant the effort.


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## l88m22vette (Mar 2, 2006)

opcorn:

As a follow-up, can anyone point me to a company that would make a decently-priced custom bar? It seems like I should just be able to send a stock bar in and have them replicate it in whatever diameter I want (say, 17mm). I heard about ADDCO and Saner Performance but haven't gotten anywhere...


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## madmax199 (Oct 28, 2009)

*

As a follow-up, can anyone point me to a company that would make a decently-priced custom bar? It seems like I should just be able to send a stock bar in and have them replicate it in whatever diameter I want (say, 17mm). I heard about ADDCO and Saner Performance but haven't gotten anywhere... *

You could have the custom bar made for you, I know some race buddies that have gone that way successfully.
I would suggest something like a 15 or a 16 mm with 3 or 4 adjustment holes drilled into the bar. From what I see on my modified stock bar, there is also room to add an inch to each arm length, so I'd add that to the list of specs.

Just curious, why don't you modify your stock bar, like I did, and see how you like it?




Front swaybar modification(reducing the bar rate)





Uploaded with ImageShack.us


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## rastta (Feb 22, 1999)

20v master said:


> A favor is something I do for courteous people. You are just being argumentative for the sake of wanting to be right. The cars share the same subframe and same dimension control arms. The front tracks are the same. Even the KW coils on my GTI have the mount for the TT style bar and link. I know the reason for the original question, and I posted an explanation of how to achieve it with some relatively simple fabrication. Again, you just want to argue that a hooped sway is impossible to make work in a TT. Yes there isn't a smaller OEM bar. Yes the question was is there a way to decrease the stock front sway rate. Yes you are just arguing to argue. No I don't have time or the desire to do the work to prove you wrong. Sorry this went on a tangent max.


Read my posts again - i've never argued that a hooped sway is impossible to make work on a TT - i've just said over and over again - that for the amount of time and effort necessary - you could simply buy a smaller TT bar and bolt it in. Or do what Max did and elongate the stock bar to reduce rate rather than use a thicker bar and mount it in a fashion it wasn't designed to be mounted and try and figure out if it's going to reduce rate or increase rate through a series of calculations.


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## rastta (Feb 22, 1999)

madmax199 said:


> No tangent, it's all part of having a good discussion.
> 
> Personally, altough I haven't seen an Mk4 bar, I don't think it's worth the trouble to try a thicker bar on the car if the goal is to reduce the rate.
> 
> ...


Here's a somewhat decent pic. 










It looks like someone put poly's in that link. Other use longer links when lowering to increase clearance over the drive shaft.


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## madmax199 (Oct 28, 2009)

[email protected] said:


> Here's a somewhat decent pic.
> 
> 
> 
> ...


Thanks for the picture Joe!

As ironic as this is going to sound, I think that this bar has the potential to be modified to be softer than the elongated one in my car. 

Although bigger in diameter there is more room for adding length to the vw arms because of the design.
Holes would be required to be drilled and tapped to the TT arms, but using really short linkages would leave a lot of room for elongation.

I am going to see if I can put my hand on a vw bar at the JY and start the modifications to see how much can be added to the arms within the available space:beer:.


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## 20v master (May 7, 2009)

No max, its not worth the time or effort. :sly:


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## Doooglasss (Aug 28, 2009)

What about the haldex driveshaft and our exhausts? Is there clearance for them with the mk4 bar?

I know the subframe is the same on both cars but I have no idea if the bars are the same- since I've never owned a mk4 VW.


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## madmax199 (Oct 28, 2009)

Good point Doug, I guess the only way to find out is to try it.

When I get the bar I will make the calculations to figure out the rate and see if it's worth the trouble making it fit.


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## Doooglasss (Aug 28, 2009)

Alternatively I know Ed just got a pipe bender and I have my stock bars hanging in the garage if you want to reproduce them... Could use some 1/2" conduit or something.


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## rastta (Feb 22, 1999)

DougLoBue said:


> What about the haldex driveshaft and our exhausts? Is there clearance for them with the mk4 bar?
> 
> I know the subframe is the same on both cars but I have no idea if the bars are the same- since I've never owned a mk4 VW.


From the pics I looked at the TT has a bend in it for clearance of the driveshaft.


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## madmax199 (Oct 28, 2009)

I got a few PM about swaybars calculations(thanks Joe and 20V ) 

So, for any *conventional swaybars* this would be the measurements required to calculate a swaybar rate (the VW mk4 bar that somehow made it into the discussion would require a more involved approach) 

 

Uploaded with ImageShack.us 

Anyone with A B C D can either post them or PM me and I'll be able to tell you the bar rate. 



While I'm at it, I'm going to post how *Motion Ratios* are calculated. I have been mentioning motion ratios because they greatly affect the wheel rates and spring choices(for example, any coilover with stiffer front springs in a TT is crap , I don't care who makes it) 

The numbers inputed, at the bottom here, are for the front of a stock TT (camber plates, change this number slightly because of the shock angle, in relation to the control arm) 
While the diagram( top) show how the spring is mounted inboard in the back of the TT. 



 

Uploaded with ImageShack.us 




The next few pictures are screen shots off various parameters involved in modeling the suspension in my TT. Usually people don't release these numbers because it's hard work, and they would not want someone else to just copy the set up that makes them fast; but that's not my type (I should point out that the numbers are not going to be the same for your TT because of the variables like ride height, spring rate, swaybar etc.) 


Current spring rates 

 

Uploaded with ImageShack.us 

Swaybar rates, plotted with bushing and linkage deflection. 
(blue is front and red is rear, you can also notice how my front bar rate is reduced, when compared to the much smaller rear stock bar) 

 

Uploaded with ImageShack.us 


Tire size and deflection 

 

Uploaded with ImageShack.us 

Current wheel rates (I keep saying current because I'm about to put 1300 lbs rear springs in the car since my wife doesn't drive it anymore and I could use more rear rate) 

 

Uploaded with ImageShack.us 

Dynamic loads in a 1.2 G steady state left turn (excuse the bimmer pic, it was engraved when the program was built). At 1.2G with the current set up I still have all 4 wheel on the ground, wich is good. 


 

Uploaded with ImageShack.us 

Since I mentioned that I will put stiffer springs in the back for a more optimal wheel rate, I should post the effect it will have on the car's behavior (that's the beauty of modeling a suspension, you can tell in advance what a modification is going to do). 

New rear spring rate of 1300lbs 

 

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New dynamic behavior with the 1300lbs springs and same 1.2 G left turn 
The right rear tire is slightly unloaded and off the ground but not by much( negative number in red, by the bimmer's left rear tire, illustrates a wheel in the air). I will be compromising some traction at 1.2G and up, but will gain a lot more grip under 1.2G force and better front weight distribution when loaded. So overall, it's worth it :beer::beer::beer:. 

 

Uploaded with ImageShack.us


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## rastta (Feb 22, 1999)

madmax199 said:


> I got a few PM about swaybars calculations(thanks Joe and 20V )


 Hey don't blame me!  

I'm in the process of going through this with my S4. Need to confirm some of the measurements. 

One thing that comes to mind is how the swaybar attaches and swaybar links and how they affect overall swaybar stiffness. This comes to mined because when fitted with thick aluminum adjustable sway bar links - my rear bar on the TT felt stiffer.


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## madmax199 (Oct 28, 2009)

[email protected] said:


> Hey don't blame me!
> 
> I'm in the process of going through this with my S4. Need to confirm some of the measurements.
> 
> One thing that comes to mind is how the swaybar attaches and swaybar links and how they affect overall swaybar stiffness. This comes to mined because when fitted with thick aluminum adjustable sway bar links - my rear bar on the TT felt stiffer.


 In theory links are not suppose to affect the swaybar rate. However, if the link is adjustable and/or binding it will be pre-loading the bar. That will affect the bar feel and stiffness especially side to side. 

Swaybars, for example, *should never be attached to the end links while the tires are on the air*. This causes natural preload, greatly affecting the bar's stiffness left and right. The same goes for end links, even unloaded, they can, if slightly putting stress on the bar, change the dynamics. 

What program do plan on using? 

If it's mine, bushing deflection is taken into account in the swaybar rate section- as they are the one thing that can substantially impact the bar rate and behavior. 

The bar rate graph on the bottom right of the appropriate section(the graph that I posted) show the corrected curves with poly bushing stiffness used as a default. If you are using rubber bushing, the bushing deflection would've to be adjusted to take into account their softer nature. 

If you have other questions, let me know and I'll gladly point you in the right direction.


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## rastta (Feb 22, 1999)

madmax199 said:


> In theory links are not suppose to affect the swaybar rate. However, if the link is adjustable and/or binding it will be pre-loading the bar. That will affect the bar feel and stiffness especially side to side.
> 
> Swaybars, for example, should never be attached to the end links while the tires are on the ground. This causes natural preload, greatly affecting the bar's stiffness left and right. The same goes for end links, even unloaded, they can, if slightly putting stress on the bar, change the dynamics.
> 
> ...


 Ok - i'll look at bushing rate deflection - since i'll be replacing standard VAG links on my S4 rear with heim jointed adjustable links. 

Will you be increasing rear camber with the higher spring rate in the rear?


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## madmax199 (Oct 28, 2009)

[email protected] said:


> Ok - i'll look at bushing rate deflection - since i'll be replacing standard VAG links on my S4 rear with heim jointed adjustable links.
> 
> Will you be increasing rear camber with the higher spring rate in the rear?


 In fact, my static rear camber settings will have to be decreased from the -2.5 that I have them set right now. With less rear roll, less static camber will be needed to keep the tire perpendicular to the road(flat contact patch) when fully loaded. 

I love this picture because it clearly illustrated that at full load, the driver side front tire is perfectly vertical to the road and parallel to that light post on the upper right of the pic. It is difficult to nail and highly desirable because it's the perfect balance of traction vs roll. 

*Picture of the fastest time of the day at Waterfest 16* 
 

Uploaded with ImageShack.us 




As a reference this is what it looked like before I nailed the setup. Less roll and steering input on that turn but loaded side tires were slightly in a positive camber state( reducing the size of my contact patch and overheating the outside edges ot the tires. 

*Picture taken early last season at the SCCA DC ProSolo.* 
 

Uploaded with ImageShack.us


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## speed51133! (Aug 5, 2002)

madmax199 said:


> Swaybars, for example, should never be attached to the end links while the tires are on the ground. This causes natural preload, greatly affecting the bar's stiffness left and right. The same goes for end links, even unloaded, they can, if slightly putting stress on the bar, change the dynamics.
> .


 the bentley SPECIFICALLY says to only attach the sway bar end links when the vehicle is on the ground with the full weight on the wheels. it says attaching the end links wen the car is in the air will cause pre load..... 

did you make a mistake in the above quote?


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## madmax199 (Oct 28, 2009)

speed51133! said:


> the bentley SPECIFICALLY says to only attach the sway bar end links when the vehicle is on the ground with the full weight on the wheels. it says attaching the end links wen the car is in the air will cause pre load.....
> 
> did you make a mistake in the above quote?


 Good catch and I stand corrected :thumbup:, I meant to say "*swaybar should never be installed with the tire in the air*" 

The correct way to do it is to even have the driver's weight in the seat at race weight to get a perfectly un-binded bars.


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## rastta (Feb 22, 1999)

madmax199 said:


> In fact, my static rear camber settings will have to be decreased from the -2.5 that I have them set right now. With less rear roll, less static camber will be needed to keep the tire perpendicular to the road(flat contact patch) when fully loaded.


 Ok - that makes sense - I take this was based upon tire temp readings as well. I was thinking that with a higher spring rate, you might have more trouble keeping the contact patch down when you hit bumps etc. and slightly more camber might help in that situation.


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## madmax199 (Oct 28, 2009)

[email protected] said:


> Ok - that makes sense - I take this was based upon tire temp readings as well. I was thinking that with a higher spring rate, you might have more trouble keeping the contact patch down when you hit bumps etc. and slightly more camber might help in that situation.


 Yes, temp reading will be used to let me know how much negative camber to remove to get an even spread across the tire after a run. 

In general, *static* negative camber is used to compensate for body roll and the resulting camber loss, in full *dynamic* situations. With stiffer springs, you get less roll and the camber loss through the geometry is less dramatic, so it requires less static compensation.


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## Doooglasss (Aug 28, 2009)

Could you guys please explain the reasoning behind attaching the sway bar links when the car is on the ground and how you pull it off without being on an alignment rack?

This is something I've never done on my car- I've always attached the endlinks before lowering the car, I figure since the sway bar pivots in it's bushings then it shouldn't be an issue?


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## madmax199 (Oct 28, 2009)

DougLoBue said:


> Could you guys please explain the reasoning behind attaching the sway bar links when the car is on the ground and how you pull it off without being on an alignment rack?
> 
> This is something I've never done on my car- I've always attached the endlinks before lowering the car, I figure since the sway bar pivots in it's bushings then it shouldn't be an issue?


 The reasoning is that, if you have the links attached in the air, they will start binding when the suspension compresses back when at rest on the ground. Even a slight binding put substantial preload on the bar. 

The way I do it, just like my garage alignments, is put the car on four blocks that I leveled with digital angle finder. With ballasts in the drivers seat, to simulate my weight, I then crawl under the car and attach the links while making sure that there is free play. 

I bet you have some preload and your reaction left to right is not even as a result.


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## rastta (Feb 22, 1999)

madmax199 said:


> Yes, temp reading will be used to let me know how much negative camber to remove to get an even spread across the tire after a run.
> 
> In general, *static* negative camber is used to compensate for body roll and the resulting camber loss, in full *dynamic* situations. With stiffer springs, you get less roll and the camber loss through the geometry is less dramatic, so it requires less static compensation.


 Yeah - in looking at my tire temps and wear patterns - fronts are spot on at 2.75 degrees negative camber - but my rears are a bit of a mystery. In the rear tire temps are a bit colder inside and get warmer as they move to the outer edge. However - in looking at the wear pattern - the inside appears to be wearing a bit more than the outside. Not a lot but it is noticeable. I'm running -1.9 camber in the rear - which is max without adding adjustable upper control arms which are near $600 a set and different adjustable toe links for another $300. I would have thought that based upon tire temp readings that I'd need more camber - but wear is telling me otherwise.


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## madmax199 (Oct 28, 2009)

[email protected] said:


> Yeah - in looking at my tire temps and wear patterns - fronts are spot on at 2.75 degrees negative camber - but my rears are a bit of a mystery. In the rear tire temps are a bit colder inside and get warmer as they move to the outer edge. However - in looking at the wear pattern - the inside appears to be wearing a bit more than the outside. Not a lot but it is noticeable. I'm running -1.9 camber in the rear - which is max without adding adjustable upper control arms which are near $600 a set and different adjustable toe links for another $300. I would have thought that based upon tire temp readings that I'd need more camber - but wear is telling me otherwise.


 What you are describing is "text book" symptomatic of a car with not enough rear wheel rate. 

Even with enough static camber compensation to impact tire wear(inside wearing out faster), you are still overworking the outer portion of the contact patch because of the excessive roll. 

Just like me, you need more rear wheel rate and you will not require as much static camber compensation. The smart way to cure that, is to bump your spring rate. Making your rear bar stiffer, would also increase your wheel rate but at the expense of some grip and traction(you could do that for now until you get the right springs so you don't chew your rubber). 

Remember that an increase in spring rate may require re-valving of the shocks (if you run out of your valving window). That's why I'm such a big fan of Bilsteins inverted monotubes, they offer a wide valving window because of the huge piston and cylider size.


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## rastta (Feb 22, 1999)

madmax199 said:


> What you are describing is "text book" symptomatic of a car with not enough rear wheel rate.
> 
> Even with enough static camber compensation to impact tire wear(inside wearing out faster), you are still overworking the outer portion of the contact patch because of the excessive roll.
> 
> ...


 I've been debating about increasing my spring rates front and rear but this pretty much seals that deal. I have a set of Hotchkis bars waiting to be installed - but haven't installed them because I just wasn't sure about spring rates. 

I've got Penske 7500's in the car (they are only rebound adjustable) which were just recently rebuilt and re-valved by Performance Shock at Sears Point to handle 1000 lb springs in the front and 1200's in the rear - since I thought I'd most likely be increasing the spring rates. 

Now to figure out what rates to go with.......


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## madmax199 (Oct 28, 2009)

Finding the right spring rate is more art than science. The suspension calculator will get you in the ballpark but can't accurately predict driving style and preferences , track surfaces etc. 

Word of advice, start soft and increase accordingly because you get a car that is usable on bumpy and smoother tracks. You may suffer a little on high grip surfaces( concrete, banked turns) but the car will be right at home pretty much everywhere until you nail the setup. 

High rollers, have an optimal set of springs for every track, but for a budget racer like me, I optimize for the biggest event of my season(auto-x nationals or road racing runoffs ). 

I hope this help you in your decision. 

I almost forgot: rear natural frequency around 3 Hz and front natural frequency around 2.7-2.8 Hz is my personal ballpark for a racecar relying mostly on mechanical grip and limited aero.


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## seth_3515 (Dec 26, 2008)

madmax.. you have given me a wonderful read! I really appreciate it! I personally believe, that your calculations will be sufficient for any tuner on this forum.. Suspension rates, settings, and available kits make a daunting task for the uninformed user, but you have definitely given the uninformed user an amazing general map to follow when selecting suspension components and settings.. :thumbup:


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## rastta (Feb 22, 1999)

madmax199 said:


> Finding the right spring rate is more art than science. The suspension calculator will get you in the ballpark but can't accurately predict driving style and preferences , track surfaces etc.
> 
> Word of advice, start soft and increase accordingly because you get a car that is usable on bumpy and smoother tracks. You may suffer a little on high grip surfaces( concrete, banked turns) but the car will be right at home pretty much everywhere until you nail the setup.
> 
> ...


 Thanks for the tips on frequency's - been reading up on it as well. Alot of my base info was based upon what Stasis did with their cars as well as talking to 034 Motorsports but most of what was done to S4's and the like was done 6-10 years ago and not many still running them. 

Part of my concern about spring rate has alot to do with track surface and ability to handle a variety of surfaces. However - the tracks I run on are on in pretty good condition surface wise. They are quite different in nature though - with Sears Point being extremely technical, Thunderhill be a bit more wide open and Laguna Seca being a bit of both.


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## madmax199 (Oct 28, 2009)

seth_3515 said:


> madmax.. you have given me a wonderful read! I really appreciate it! I personally believe, that your calculations will be sufficient for any tuner on this forum.. Suspension rates, settings, and available kits make a daunting task for the uninformed user, but you have definitely given the uninformed user an amazing general map to follow when selecting suspension components and settings.. :thumbup:


 I'm glad that some apreciate it! 

There was a time I was blind myself when it comes to suspension tuning and had to turn to others to fully grasp everything that's involved (having an automotive/mechanical background also hepled). Now it's my time to help others with what I know.


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## madmax199 (Oct 28, 2009)

[email protected] said:


> Thanks for the tips on frequency's - been reading up on it as well. Alot of my base info was based upon what Stasis did with their cars as well as talking to 034 Motorsports but most of what was done to S4's and the like was done 6-10 years ago and not many still running them.
> 
> Part of my concern about spring rate has alot to do with track surface and ability to handle a variety of surfaces. However - the tracks I run on are on in pretty good condition surface wise. They are quite different in nature though - with Sears Point being extremely technical, Thunderhill be a bit more wide open and Laguna Seca being a bit of both.


 You are welcome Joe, 

Like I said, start on the soft side with 2.7 Hz - 3 Hz front to back. Use minimal bar to trim the balance to your driving style and liking( a sligthly loose car from mid corner out is desirable ). 
Fine tune everything with tire size and pressure and you should be good to go. 
Don't hesitate to pick my brain with any questions you may have, that's what I do everyday at work anyway. 

BTW Laguna Seca, to me is the most fun track in the US. Technical, yet flowing with big elevation changes (the corque screw is the icing on the cake), you are blessed to have it local to you. Here in the north east, New Hampshire is the only track I don't catch myself falling asleep because of the uphill "on camber" hairpin after the front straight. (lots of action)


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## rastta (Feb 22, 1999)

madmax199 said:


> You are welcome Joe,
> 
> Like I said, start on the soft side with 2.7 Hz - 3 Hz front to back. Use minimal bar to trim the balance to your driving style and liking( a sligthly loose car from mid corner out is desirable ).
> Fine tune everything with tire size and pressure and you should be good to go.
> ...


 Sears is my favorite by a long shot. Once you get going - you can get in a rhythm that is simply unbeatable. I like Laguna - but with lots of long uphill straights out of turns (5 and 6) - high hp cars have an advantage. I can't wait to get the S4 out there. Last time I was there - I lost a motor mount on the TT and the DP took out a fitting on my steering rack.


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## 320hpBlackTT (Dec 25, 2008)

Ok please forgive me I dont want to get crucified but I know absolutely nothing about suspension :banghead: I got HPA ST coilovers coming in the mail and I have no idea what I need so I dont mess up my tires and or car haha. I just want to drop it a little to get rid of wheel gap and am pretty much only lowering for looks anyway. I guess my question is at what point do I need adjustable control arms? sway bars? etc I have no clue whats going on so any advice would be amazing


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## madmax199 (Oct 28, 2009)

320hpBlackTT said:


> Ok please forgive me I dont want to get crucified but I know absolutely nothing about suspension :banghead: I got HPA ST coilovers coming in the mail and I have no idea what I need so I dont mess up my tires and or car haha. I just want to drop it a little to get rid of wheel gap and am pretty much only lowering for looks anyway. I guess my question is at what point do I need adjustable control arms? sway bars? etc I have no clue whats going on so any advice would be amazing


Don't lower more than an inch (especially in the front) if handling is a concern. 
Camber and toe corrections are needed in the rear, whith any kind of lowering. 
*Offset bushings * or *adjustable control arms *should bring back the alignment settings within specs in the back. 

You don't need swaybars or anything else, just a good alignment and camber/toe compensation for the rear.


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## 320hpBlackTT (Dec 25, 2008)

So with that being said do I need to buy 2 or 4 control arms? I'm a suspension noob I know


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## rastta (Feb 22, 1999)

320hpBlackTT said:


> So with that being said do I need to buy 2 or 4 control arms? I'm a suspension noob I know


One set is enough - put them on the bottom. Especially if you don't lower too much and you use a typically street based rear camber of -1.7 degrees or so and zero or up to 1/16" of toe in. The less camber you run - the harder it is to get toe into spec without using two sets.


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## 320hpBlackTT (Dec 25, 2008)

ok awesome so i only need one set phew bit of a price break haha i only want to lower it enough to get rid of the wheel gap i dont want to get crazy and scrape the ground or hit every pothole and destroy my bumper and i have no clue how to set them up haha thanks though i really appreciate it


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## rastta (Feb 22, 1999)

320hpBlackTT said:


> ok awesome so i only need one set phew bit of a price break haha i only want to lower it enough to get rid of the wheel gap i dont want to get crazy and scrape the ground or hit every pothole and destroy my bumper and i have no clue how to set them up haha thanks though i really appreciate it


I'd suggest the following as a good street alignment that won't toast your tires easily. I'd run -1.2 or so degrees of camber - which is usually as much as you can get with minimal lowering and having them be equal on both sides. Then 1/32" of toe in. I don't like zero toe or even toe out on the street because you can tend to wander a bit a higher speeds. Slight toe in helps with this - anything more than 1/16" will result in more inner tire wear.

Also make sure to put in new strut bushes and bearings when you install your new suspension.


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## madmax199 (Oct 28, 2009)

[email protected] said:


> I'd suggest the following as a good street alignment that won't toast your tires easily. I'd run -1.2 or so degrees of camber - which is usually as much as you can get with minimal lowering and having them be equal on both sides. Then 1/32" of toe in. I don't like zero toe or even toe out on the street because you can tend to wander a bit a higher speeds. Slight toe in helps with this - anything more than 1/16" will result in more inner tire wear.
> 
> Also make sure to put in new strut bushes and bearings when you install your new suspension.


Good advice Joe :thumbup:,
Personally, I like 1/32"- 1/16" of *toe in* the back, even on my performance/track cars(unless they naturally toe in under compression). It makes the car more planted and not scary to drive at high speed, rain, and uneven surfaces. A zero toe or toe out in the back of a TT, IMO is either a mistake or a statement from a driver with a lot of confidence in his driving abilities.


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## rastta (Feb 22, 1999)

madmax199 said:


> Good advice Joe :thumbup:,
> Personally, I like 1/32"- 1/16" of *toe in* the back, even on my performance/track cars(unless they naturally toe in under compression). It makes the car more planted and not scary to drive at high speed, rain, and uneven surfaces. A zero toe or toe out in the back of a TT, IMO is either a mistake or a statement from a driver with a lot of confidence in his driving abilities.


Yeah - I've never gone zero on the TT - always 1/32" to 1/16" toe in on the rear. The problem is too much rear toe eats tires because there is no toe correction - and you get pretty wild camber changes in the rear - as you know - without real stiff springs.


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## 320hpBlackTT (Dec 25, 2008)

Ok so heres what i found for bushings and bearings.....please let me know if im way off or if these are right 
http://www.ecstuning.com/Audi-TT-Quattro-/ES261062/

http://compare.ebay.com/like/370461...fa2a95f&itemid=370461814442&ff4=263602_309572

http://cgi.ebay.com/ebaymotors/FRON...dZViewItemQQcategoryZ33590QQitemZ150467376949


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## rastta (Feb 22, 1999)

320hpBlackTT said:


> Ok so heres what i found for bushings and bearings.....please let me know if im way off or if these are right
> http://www.ecstuning.com/Audi-TT-Quattro-/ES261062/
> 
> http://compare.ebay.com/like/370461...fa2a95f&itemid=370461814442&ff4=263602_309572
> ...


These are what you want - not the ECS ones - don't even know what those are. I suggest buying the OEM pieces rather than anything on eBay or even through ECS. Go through genuinevwaudiparts.com. This is the OEM part number for the bush and bearing - you need two of each.

1J0412331C
1J0412249


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## 320hpBlackTT (Dec 25, 2008)

Seriously you guys are the best! Thanks Joe I really appreciate it.....gonna do everything within the next 2-3 weeks its gonna be interesting 



[email protected] said:


> These are what you want - not the ECS ones - don't even know what those are. I suggest buying the OEM pieces rather than anything on eBay or even through ECS. Go through genuinevwaudiparts.com. This is the OEM part number for the bush and bearing - you need two of each.
> 
> 1J0412331C
> 1J0412249


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## rastta (Feb 22, 1999)

320hpBlackTT said:


> Seriously you guys are the best! Thanks Joe I really appreciate it.....gonna do everything within the next 2-3 weeks its gonna be interesting


If you have over 75-80k miles on the car - i'd highly suggest doing the sway bar links front and rear as well as possibly the front control arm bushes in the rear position which can crack with use. Other item would be the ball joints. Again - use OEM stuff - you can get the oem part numbers from ECS site - just look for the manufacturers part number on the OEM part listing.


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## 320hpBlackTT (Dec 25, 2008)

oh jesus im so lost ....just rolled over 116k.... ugh seriously though the help is really awesome i really appreciate it!


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## rastta (Feb 22, 1999)

320hpBlackTT said:


> oh jesus im so lost ....just rolled over 116k.... ugh seriously though the help is really awesome i really appreciate it!


It's ok - it's just that if you are doing all that work with suspension - you have to disconnect all the stuff I mentioned anyway and might as well refresh it.

Items 3, 10 and 18 are what i'm talking about.


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## honda93 (Oct 1, 2008)

Subscribed.


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## papasmurf133 (Jun 3, 2011)

honda93 said:


> Subscribed.


Me too.


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## madmax199 (Oct 28, 2009)

Having this thread back up top and reading the whole thing again reminded me of how awesome it was. I need to get off my lazy ass and finish the missing chapters :thumbup::thumbup::thumbup:!


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## Audi Boy TT (Feb 25, 2009)

part 3 & 4 opcorn:


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## Late__Apex (Dec 2, 2007)

Max, or anyone for that matter, do you know of a freeware or inexpensive suspension modeling software?


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## Malant (Aug 30, 2004)

Late__Apex said:


> Max, or anyone for that matter, do you know of a freeware or inexpensive suspension modeling software?


There used to be an excel spreadsheet put together by a man name Steve (known by Stretch on many forums) that I have read about which is extremely helpful and a great tool, however all links to download it are now dead and I cant seem to find anyone who has it


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## Late__Apex (Dec 2, 2007)

Malant said:


> There used to be an excel spreadsheet put together by a man name Steve (known by Stretch on many forums) that I have read about which is extremely helpful and a great tool, however all links to download it are now dead and I cant seem to find anyone who has it


I have that spreadsheet I think - Steve Edwards wrote the one I have. Shoot me a PM with your email address and I'll send it to you.

I'm looking for one that has suspension geometry.


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## madmax199 (Oct 28, 2009)

Late__Apex said:


> Max, or anyone for that matter, do you know of a freeware or inexpensive suspension modeling software?


Hey buddy, I haven't seen you around in a while! How's the build coming along?
What are you trying to model and what's the budget on software?

I usually get all the data I need by using the calculator I believe I sent you. If you use it correctly, you can get spring rates, swaybars rates, natural frequencies, wheel rates and shock valving calculated - plus you could calculate and optimize overall balance in a dynamic state at a set G-load as well as finding crucial load transfer on tires at any G-load.

Anything else I feel need to be calculated and dialed manually, camber curving, corner weight balance, static roll center height, alignment and tire pressures are all things that no software is needed to properly dial. A skidpad, tire temp probe and alignment tools are all that is really needed 
to fine tune everything.


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## Late__Apex (Dec 2, 2007)

madmax199 said:


> Hey buddy, I haven't seen you around in a while! How's the build coming along?
> What are you trying to model and what's the budget on software?
> 
> I usually get all the data I need by using the calculator I believe I sent you. If you use it correctly, you can get spring rates, swaybars rates, natural frequencies, wheel rates and shock valving calculated - plus you could calculate and optimize overall balance in a dynamic state at a set G-load as well as finding crucial load transfer on tires at any G-load.
> ...


I want to play around with suspension pickup points and how it affects roll and camber change. I could build a spreadsheet to do this but it would be somewhat time consuming for what would be pretty much a one-project analysis. My budget should be reflected in the fact that I mentioned freeware first, lol.

The project is moving. I've decided that instead of building to class, I'm going to build to taste and take whatever class that puts me into with NASA.


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## madmax199 (Oct 28, 2009)

Late__Apex said:


> I want to play around with suspension pickup points and how it affects roll and camber change. I could build a spreadsheet to do this but it would be somewhat time consuming for what would be pretty much a one-project analysis. My budget should be reflected in the fact that I mentioned freeware first, lol.
> 
> The project is moving. I've decided that instead of building to class, I'm going to build to taste and take whatever class that puts me into with NASA.


Very cool, if you are thinking about changing pick up points on existing parts - or even better, introducing all new arms/links and building the geometry from scratch (I say go for unequal length double A arms with zero roll couple ) 

I don't know of any "free budget" software that can do what you are looking to do. However, like in the pre-computer era, everything can be calculated manually if you know the basic measurements ( the spreadsheet I sent you will get you pretty far). I you know the weight, length of components and where you will have your pick up points, you could do the camber curving, find the CG, place the roll center and decide your roll couple. 

Roll and weight transfer are affected by so many variables that are independant of pick up points that I wouldn't place too much emphasis on trying to find their correlation. Polar moment of inertia *PMI*, wheel rate, shock valving all have so much bearing on roll and the way weight is transfered that you'd better off focus on placement of your CG , roll center, roll couple and just do the camber curving for the possible new pick up points.


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## madmax199 (Oct 28, 2009)

Audi Boy TT said:


> I get the motion ratio reducing the spring rate in the back but how do you determine what effective spring rate to install in your car. (sorry if I'm babbling because I'm extremely tired).
> 
> I am curious to understand how to choose a spring rate for a specific setup. Max, I see you've setup your rear at 1300 or 1100 (I'm not sure if you changed it or not) and if I read correctly 685 in the front. How did you come to choose these rates. Is it to make the spring rates effectively the same front to back? is it to change a theoretic weight distribution?
> 
> ...


Very good question that belongs in my suspension thread floating around, maybe I'll copy and paste it to where it belongs!

Choosing spring rates can be subjective but there is some rational physics behind it that dictates what is optimal. As a first guideline, there are recommended Natural Frequencies(NF) for the purpose 
of the car. For example, a car that see double duty street/track, the recommended NF is between 2.7-3.0 Hz. ( a sporty street car only needs 2-2.5 Hz).

Now that you have a ball park where to start, the real work begins, ideally you want the least amount of spring possible to keep the car flat when turning ( around one degree of roll at full load ). Another thing that comes into play is that you want the rear wheel rates to be stiffer than 
the front because of the following - when the car hits a bump or an imperfection on the road , the front reacts first than the rear follows. Because the front reacted first, it also settles first( the rear is 
still oscillating), so what you do to make the car take a set at the same time? Make the rear react/settle faster by setting the rear springs stiffer than the front (0.5 Hz alway worked for me but others have even put more than that). 

There are softwares to help the process, I have a calculator that I can email to you that can make the task a cake, as long as you know what you are doing. As far as ordering "off the shelf" coilovers and having them valved with specific spring rates, only higher brands give that option. For example 
the AST coilovers for the platform can be ordered through Vorshlag valved with whatever springs you want. Bilstein does the same thing but you'd have to order directly from them and not a vendor. I have H&R RSS coilovers( Bilstein based) and just sent them to Ramone at Bilstein California to be valved to my specs ( sorry specs are top secret). The following list are all good shocks that can be custom valved:

-Bilstein pss/pss9
-H&R street and my favorite RSS ( my final spring rate is 700/1300)
-koni true specs ( made to order)
-Ground control Advance Designs ( have to order through ground control only)
-AST 4000 and 5000 series ( ordered through Vorshlag only)
-Motons ( big baller)
-Penske ( big baller)

*This video of my car a Waterfest autocross ( not me driving ) illustrates how the car is suppose to stay flat when cornering and the tire should stay in a happy spot through the camber curve.*
http://www.youtube.com/watch?v=EBt0oO2J6q4


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## Audi Boy TT (Feb 25, 2009)

So the ideal way to do it is first find the right spring rate for your desired setup. and then revalve the shocks for a specific hertz number depending on your goals?
(I'm assuming that the shocks are the main determining factor of the hertz number?

so what is the right order to piece the suspension together. because by changing one aspect of the setup it seems that everything else is affected. I.E: if I change out my bushings to a harder setup then the car will be tighter in the corners so would i dial the spring rates back accordingly to keep the hertz where you want it?


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## madmax199 (Oct 28, 2009)

Audi Boy TT said:


> So the ideal way to do it is first find the right spring rate for your desired setup. and then revalve the shocks for a specific hertz number depending on your goals?
> (I'm assuming that the shocks are the main determining factor of the hertz number?
> 
> so what is the right order to piece the suspension together. because by changing one aspect of the setup it seems that everything else is affected. I.E: if I change out my bushings to a harder setup then the car will be tighter in the corners so would i dial the spring rates back accordingly to keep the hertz where you want it?


Correct, the right order is to first determine the optimal spring rates, then have the shocks valved to control the choosen rate and finally bring swaybars into the equation as trim pieces to fine tune the overall balance. The hertz number is from the springs and simply put, the frequency at which they oscillate up and down before they settle down. 

Busing have no real bearing in the wheel rate and overall stiffness, it's the slop between articulations that they take out ( the calculator I use have a provision for imputing various bushing stiffness although it's negligible ) The stiffer feel is associated with having less play in between the suspension and the chassis/you and more NVH is transferred.

PS: You will get that promised call today so I can take a look at the car for you!


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## Audi Boy TT (Feb 25, 2009)

awesome. I must say this discussion is getting me excited to start the tinkering and if future budget graces me with a second car auto x sounds like a blast.


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## 320hpBlackTT (Dec 25, 2008)

madmax199 said:


> Correct, the right order is to first determine the optimal spring rates, then have the shocks valved to control the choosen rate and finally bring swaybars into the equation as trim pieces to fine tune the overall balance. The hertz number is from the springs and simply put, the frequency at which they oscillate up and down before they settle down.
> 
> Busing have no real bearing in the wheel rate and overall stiffness, it's the slop between articulations that they take out ( the calculator I use have a provision for imputing various bushing stiffness although it's negligible ) The stiffer feel is associated with having less play in between the suspension and the chassis/you and more NVH is transferred.
> 
> PS: You will get that promised call today so I can take a look at the car for you!


Max I have to say I'm happy I looked at this thread again ....your one of the most knowledgeable people on here ....mad props for doing everything the right way 

Sent from my PC36100 using Tapatalk


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## madmax199 (Oct 28, 2009)

320hpBlackTT said:


> Max I have to say I'm happy I looked at this thread again ....your one of the most knowledgeable people on here ....mad props for doing everything the right way
> 
> Sent from my PC36100 using Tapatalk


Thanks again for those pics brother :beer:!


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## 320hpBlackTT (Dec 25, 2008)

madmax199 said:


> Thanks again for those pics brother :beer:!


Anytime Max! We need to catch a beer sometime :beer: you going to the Vag fair?

Sent from my PC36100 using Tapatalk


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## Audi Boy TT (Feb 25, 2009)

hey Max, I know it's not directly suspension related but how does a haldex controller or even a front or rear diff affect the TT's handling characteristics. and how do you go about tuning your suspension when your driveline begins to correct the handling issues of a TT. like the Haldex reducing oversteer or a front TBD (like the peloquin) getting power to the outside wheel better. 

Does this effect desired spring rates for front to back?(haldex)

Does it change your camber angles in corners at all due to added traction to the outside?(peloquin)

and would these Mods help or hurt your handling in general?


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## 20psi now (Feb 26, 2009)

:wave: max you now have a pm......


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## madmax199 (Oct 28, 2009)

*


20psi now said:



:wave: max you now have a pm......

Click to expand...

*will reply shortly!

*


Audi Boy TT said:



hey Max, I know it's not directly suspension related but how does a haldex controller or even a front or rear diff affect the TT's handling characteristics. and how do you go about tuning your suspension when your driveline begins to correct the handling issues of a TT. like the Haldex reducing oversteer or a front TBD (like the peloquin) getting power to the outside wheel better. 

Does this effect desired spring rates for front to back?(haldex)

Does it change your camber angles in corners at all due to added traction to the outside?(peloquin)

and would these Mods help or hurt your handling in general?

Click to expand...

 *

Another good question:thumbup:! 

Differentials affect traction and traction loss while in two of the turning phases (turn-in and exit) is often mistaken for handling or suspension deficiencies. If you are braking deep, either by choice or by mistake, a rear limited slip will have a huge bearing on the car's behavior. 
The same goes for exiting a turn, where having a front LSD or not, dictates how early you can apply throttle without understeering out of line.

Personally, I like to keep handling and mechanical traction separated because very often people tend to throw differentials at a car that has handling problems and that only mask a problem that has not been resolved. The ideal thing to do is to fix all the suspension problems, then move towards optimizing dynamic mechanical traction with the diffs. *Also to answer your question, traction dynamics and the differentials that's providing it, does not affect the choice of spring rates, camber settings etc.*

To be more TT specific, the AWD platform could really use the help of a rear differential (clutch type is prefered because there is a risk of lifting a rear wheel with the platform). A rear diff will allow to drive the car more with the throttle to steer it in the right direction. With the stock diffs you need to let the car turn then get back on it, while you'll be able to "point and shoot" with a good rear lsd. The front is not as problematic because there is never any wheel lift and always some load on the inside tire but there is room for improvement. 

The haldex controller is a must, if traction and handling is the goal. I think the orange controller is the one to get, mainly for the advantage it provides by staying locked under braking.
I barely get front wheel spin differential in my car because the suspension is working so well and that makes the stock controller not send power to the back unless I'm fully on the throttle (not a good thing). 

*With that said, the suspension is where the big problems are and where the bigger gains are going to come from, so that is where the focus should be first.*

(The fake rain last sunday really played us, I didn't think it was going to be nice all day to go autocrossing the cars!)


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## 20v master (May 7, 2009)

madmax199 said:


> Personally, I like to keep handling and mechanical traction separated because very often people tend to throw differentials at a car that has handling problems and that only mask a problem that has not been resolved. The ideal thing to do is to fix all the suspension problems, then move towards optimizing dynamic mechanical traction with the diffs. *Also to answer your question, traction dynamics and the differentials that's providing it, does not affect the choice of spring rates, camber settings etc.*
> *With that said, the suspension is where the big problems are and where the bigger gains are going to come from, so that is where the focus should be first.*


^^^ Shortened Cliff's Notes version of above post! :thumbup::thumbup::thumbup:

When modeling suspension dynamics, there is no need to add the variable of FWD vs RWD vs AWD, unless you're dealing with drift or rally where traction may be limited by surface or by choice. The natural weight distribution of the three different powertrain types are what affect the handling more than where the actual drive wheels are. :thumbup:


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## taverncustoms (Feb 18, 2011)

madmax199 said:


> I would run 750/1300 springs front to back but the high natural frequency wouldn't be too appropriate for street duties.



i for got to ask when i order custom springs what is the hight of the spring for a 3/4-1" drop? stock curb of course +-300lbs


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## Audi Boy TT (Feb 25, 2009)

madmax199 said:


> (The fake rain last sunday really played us, I didn't think it was going to be nice all day to go autocrossing the cars!)


Yea i saw the weather. it said sunny on saturday and 70% chance of rain sunday so i installed the TIP on saturday and right as im in the middle of it it rains. then i decide to pass on the autoX and its dry.

oh just for saying it. the TIP does nearly nothing.

Max I've also been applying your lessons of suspension to Forza the driving game, now that I've learned a little about suspension logic I've found out that the game is very general when it comes to car tuning but I think its good practice as far as understanding the affects of suspension tweaking.


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## Sutt (Jun 28, 1999)

You have PMs Max. :thumbup:


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## Cspence (Nov 23, 2008)

Great thread with lots of info! One thing I didn't see mentioned was whether or not adjustable sway bar end links (Front and/or Rear) are required when lowering the car. Also, I know for the rear, adjustable control arms are used to dial in camber & toe when lowering a car, but what is required for the front. I only plan on going about 1.5" and was not sure if the slotted balljoint holes offered enough adjustabiity to correct any camber issues. I occassionally hear people mention camber plates, but I'm not sure if and/or when they would be required.


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## Late__Apex (Dec 2, 2007)

Cspence said:


> Great thread with lots of info! One thing I didn't see mentioned was whether or not adjustable sway bar end links (Front and/or Rear) are required when lowering the car. Also, I know for the rear, adjustable control arms are used to dial in camber & toe when lowering a car, but what is required for the front. I only plan on going about 1.5" and was not sure if the slotted balljoint holes offered enough adjustabiity to correct any camber issues. I occassionally hear people mention camber plates, but I'm not sure if and/or when they would be required.


Adjustable sway bars are intended as a oversteer/understeer balancing tool and are not related directly to lowering. So, not required.

The OEM control arm slots should allow camber to within spec on a lowered car. Camber plates are intended to add additional camber (up to about -2.5 degrees) and to allow easier adjustment for fine tuning. They also eliminate the soft rubber strut mount for improved response.


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## madmax199 (Oct 28, 2009)

Cspence said:


> Great thread with lots of info! One thing I didn't see mentioned was whether or not adjustable sway bar end links (Front and/or Rear) are required when lowering the car. Also, I know for the rear, adjustable control arms are used to dial in camber & toe when lowering a car, but what is required for the front. I only plan on going about 1.5" and was not sure if the slotted balljoint holes offered enough adjustabiity to correct any camber issues. I occassionally hear people mention camber plates, but I'm not sure if and/or when they would be required.


Chris, adjustable swaybar links are a good idea to keep the bar unloaded and bind free at rest, especially when heavilly lowered. However, it's not a necessity at all for a 1.5" drop, only cars that are slammed will definitely need some adjustments to stay within the allowable misalignment of the end links . 

As far as camber is concerned in the front, lowering does not affect the static camber like it does in the back (different geometry). The OEM front control arms are slotted to allow some *minor* camber adjustments (if you want more, maybe to dial a more agressive static camber and get better tire contact patch in dynamic state , you'd need excentric bushings or camber plates. They usually allow up -2.5 of static camber, wich is somewhat decent in terms of handling). Lowering the front would change toe considerably too, just like the rear, but an alignment easily takes care of that. :beer::beer::beer: you need it after not having power for almost a week


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## TheDeckMan (Sep 26, 2004)

madmax199 said:


> Chris, adjustable swaybar links are a good idea to keep the bar unloaded and bind free at rest, especially when heavilly lowered. However, it's not a necessity at all for a 1.5" drop, only cars that are slammed will definitely need some adjustments to stay within the allowable misalignment of the end links .
> 
> As far as camber is concerned in the front, lowering does not affect the static camber like it does in the back (different geometry). The OEM front control arms are slotted to allow some *minor* camber adjustments (if you want more, maybe to dial a more agressive static camber and get better tire contact patch in dynamic state , you'd need excentric bushings or camber plates. They usually allow up -2.5 of static camber, wich is somewhat decent in terms of handling). Lowering the front would change toe considerably too, just like the rear, but an alignment easily takes care of that. :beer::beer::beer: you need it after not having power for almost a week


:thumbup:


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## The_RoadWarrior (Nov 21, 2011)

DeckManDubs said:


> :thumbup:


looks like this guy knows his suspension


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## Malant (Aug 30, 2004)

The_RoadWarrior said:


> looks like this guy knows his suspension


I would say a little more than that 

:wave::heart:


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## 3.1415 (Jun 15, 2009)

*TT autocross prep*

Bringing this thread back. I've been a member for awhile here, mostly a lurker. I have a 914 that I turbocharged and have autocrossed for 10+ yrs. It has turned into a stiffly sprung cone killer. I've grown a little tired of no heat in the spring, and no a/c in the summer, and after a long day in the sun, thats a deal. Thinking of a couple seasons in the TT, in either GS or STC. 

About the car: Its a 2000 fwd TT, purchased from the original owner, that has not been subjected to the factory "updates". The only change from the way it rolled out of the showroom is a replacement set of Blisteins. I have copies of about a billion letters Audi USA sent him offering the "upgrades", and a letter from the owner requesting/telling Audi USA and his dealer that is was quite well satisfied with the car as it was and to STOP pestering him about the updating. The car is a street car and needs to be (sort of) comfortable for a 140 mile a day commute. 

GS quesitons: I need to run a 7" rim, as thats whats on it now. What is the widest chunk of Hoosier that I can fit in the fenderwells? Anyone have a favorite rim that is L I G H T E R than the factory fat fives on it now? And now, the suspension questions. Anyone know if Audi ever authorized use of "crash bolts" on the TT? Here is the SCCA rule on crash bolts: 

"E. If offered by the manufacturer for a particular model and year, the use of shims, special bolts, removal of material to enlarge mounting holes, and similar methods are allowed and the resulting alignment settings are permitted even if outside the normal specification or range of specifications recommended by the manufacturer." 

And on to sway bars. The rules have changed, as in past years, only the front bar was fair game to be swapped out. Now you can change ONE bar on the car. Would I be better off with a bigger front bar, or an additional rear bar, as the factory bar is welded to the car? I'm not even sure the ADDITION of a bar, vs the REPLACEMENT of a bar would be legal, but the car is going to be used locally only, and as CDI for the club, I don't think anyone would care to much. Adjustable shocks would be nice, but maybe a little out of budget, given the fresh 'steins on the car now, and no real need to replace them just yet. 

STC questions: 7.5" rim, 225 tire, 140 treadwear. Can use any combo of springs, shocks, bars. The car came with some Eibach lowering springs in the box, 1567.140. They are noted as being a "progressive" rate spring, but no rates are listed on the box. They state they will lower the car 1-1.5". In keeping with a slightly budget build, (not looking to go to nationals with this car) I could run the car locally with the Bilsteins, Eibachs, and come up with a wheel and tire package. What about sway bars? Replace either, or both? If so, with what? I know, knowing the spring rates would make the bar decision easier. And for that matter, custom rate coil overs with re-valved shocks would be the best, but looking to work with what I've got going on now. 

Since this was one of the best threads I've bumped into so far on suspension and set up, I thought I'd pose these questions here for discussion. Thanks for any suggestions- 

Dave


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## 20v master (May 7, 2009)

I don't know stock spring rates so can't help you there, but the sway bar stiffness level of different bars could be reasonably approximated to help you make your choice. That said, the OEM rear sway bar is not a sway bar in the traditional sense. You'd be much better off adding an aftermarket rear sway bar than messing with the front at all (on the FWD platform).


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## Doooglasss (Aug 28, 2009)

With the new arrival of adjustable sway bar links to the TT community I'm proposing the question to the suspension captain over here--

Does changing the length/thickness/maybe even bushing type of the links change the sway bar rate?


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## 20v master (May 7, 2009)

DougLoBue said:


> With the new arrival of adjustable sway bar links to the TT community I'm proposing the question to the suspension captain over here--
> 
> Does changing the length/thickness/maybe even bushing type of the links change the sway bar rate?


Length of link? And material and thickness of bushing? The softness of the bushing/link end would allow more play thereby slightly defeating the spring rate of the bar. Length of the link doesn't play a roll unless the axis of force was in such an odd angle than most of the force was "slipping" towards the bar by simply rotating the link instead of applying actual force on the bar. The width of the bar, length of its arms, and diameter are the main factors in swaybar rate. The width and arm length are set by the geometry/layout of the suspension for the most part, which is why you see bars in multiple thicknesses for the same platform: that's the simplest way to affect the spring rate.

The point of the adjustable links is to remove any preload from uneven side to side height, after corner balancing or extreme changes to the geometry after lowering. They aren't meant to affect spring rate (other than removing preload, and/or not softening up like rubber).


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## Marcus_Aurelius (Mar 1, 2012)

DougLoBue said:


> With the new arrival of adjustable sway bar links to the TT community I'm proposing the question to the suspension captain over here--
> 
> Does changing the length/thickness/maybe even bushing type of the links change the sway bar rate?


Short answer = No



20v master said:


> Length of link? And material and thickness of bushing? The softness of the bushing/link end would allow more play thereby slightly defeating the spring rate of the bar. Length of the link doesn't play a roll unless the axis of force was in such an odd angle than most of the force was "slipping" towards the bar by simply rotating the link instead of applying actual force on the bar. The width of the bar, length of its arms, and diameter are the main factors in swaybar rate. The width and arm length are set by the geometry/layout of the suspension for the most part, which is why you see bars in multiple thicknesses for the same platform: that's the simplest way to affect the spring rate.
> 
> The point of the adjustable links is to remove any preload from uneven side to side height, after corner balancing or extreme changes to the geometry after lowering. They aren't meant to affect spring rate (other than removing preload, and/or not softening up like rubber).


Cliffnote version is: the size, length, and bushing type does not affect the overall rate of the bar. 

What is to be noted is that the amount of deflection allowed at the pivot joints (the 2 ends of the attachment links), plays a big role in the rate or speed that the twisting forces of the bar (bar twisting from a rolling chassis) is transferred to the suspension. 

- Allow a lot of deflections at the pivot joints, and there will be delayed transfer of the bar's twisting forces.

- Remove most of the slop at the pivots, and you can get near-instant rate of transfer. This gives a more direct and responsive feel to the setup. In my car for example, I add universal poly bushes, of the proper size, over the existing mushy pivot joint boots. This eliminates most of the play mentioned above and gives me better reaction for transitional maneuvers (it is not unusual for full race cars to have completely solid attachment links on their swaybars).

Obviously, this is irrelevant to daily driving and 90% of the people reading this, but I thought it was worth mentioning to compliment your answer. :beer:


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## 20v master (May 7, 2009)

I thought this would be a better place to put this rather than continuing to clutter the track day thread. 

Taken from that thread/Max's post:



> - Need more rear wheel rate. Again, showing positive dynamic camber when loaded. Since this isn't the steering axle, it should be looked at differently. Too much rear static camber compensation, as you know, will shrink the contact patch and reduce available grip. So, more rear rate is the ticket for you on that axle. Personally, I am not a fan of the easy way out (more rear bar) because it's a compromise, where you're giving some up to gain some back (very often giving up more than what is re-gained). A bit more rear springs (say a 2k bump) should easily bring the rear roll in check at your grip level.


A picture from my recent track day:










I already have a rear sway bar, so there won't be much to gain there by finding the biggest bar possible. This means stiffer springs and revalving the shock to prevent the 3 wheeling seen here. The common misconception of 3 wheeling is "you're cornering hard, bro!!", when in reality, the available contact patch area of tire to asphault has been reduced by 25% since one tire isn't on the ground. :thumbdown:

Max, did you mean a 200# bump in spring rate? Or are we talking some non American unit like Newtons? :laugh:


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## Neb (Jan 25, 2005)

I may be way off base here, but wouldn't eliminating any extra play up front in the sway bar links/bushings help keep the rear planted as well? The front wouldn't dip as much no?


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## 20v master (May 7, 2009)

Neb said:


> I may be way off base here, but wouldn't eliminating any extra play up front in the sway bar links/bushings help keep the rear planted as well? The front wouldn't dip as much no?


I'm not sure what you're asking. I actually don't run a front swaybar, so there's no extra play to eliminate. More front swaybar = more understeer, not what I'm attempting to do. The mass of the car in the rear (weight on the two rear tires) and the effective wheel rate (spring and damper rates of rear tires, rear sway bar, rear spring and shock, all combined) are what control the rear. Obviously the front and rear are connected so they're not completely independent, but that's when you get into natural frequencies of the whole car, and has more to do with dealing with road variations (speedbumps, expansion joints, etc) than cornering ability.


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## Marcus_Aurelius (Mar 1, 2012)

20v master said:


> I thought this would be a better place to put this rather than continuing to clutter the track day thread.
> 
> Taken from that thread/Max's post:
> 
> ...


Your coilovers can take a 3k bump without needing revalving to match the springs (this comment is specific to the coilovers that Adam runs, but not necessarily the case for every brand out there). 

Using the hardware that you have, this what I'd do:

- First, I would add 2-3k more rear springs to get more rear roll rate. 

- Secondly, I would also add a little bit more front spring (small 1k increments at a time) to get front body roll back in check. The second part is to make up for the lack of front bar. I ran into the same issue when I tried the "no front bar" approach, that's why a modified bar with reduced rate went back in as happy medium between the two.

Tripod is usually a result of a combination of several things:

1) Not enough front roll resistance (this causes the front to dive way to much and roll over itself with weight transfer)

2) Too much rear bar (this removes side-to-side independence and jacks the inside rear in a turn)

3) Not enough droop travel in the rear struts (if you have say 2" of droop travel in the back... and roll angles that equates to more than 2" of travel, no matter what you do you'll pick up a rear wheel. Solution is to either increase the available droop travel with different/modified struts, or limit the roll angles to less than what would equate to 2" of rear suspension travel). 

Since we're not looking to change the rear droop (requiring hardware change/modification), increasing the roll angles is the sensible solution to keep the car flatter through turns, and maximizing grip. 



20v master said:


> Max, did you mean a 200# bump in spring rate? Or are we talking some non American unit like Newtons? :laugh:


I was talking rest of the world language, here is a spring rate conversion chart so everyone can follow


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## 20v master (May 7, 2009)

So what maker of springs do you recommend? One that can calculate spring rates based on corner weight and motion ratios? :laugh:


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## 20v master (May 7, 2009)

Max, do you also know the spring rates of the off the shelf PSS's? Knowing how much to add isn't much good without the original spring rate obviously.


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## Marcus_Aurelius (Mar 1, 2012)

20v master said:


> Max, do you also know the spring rates of the off the shelf PSS's? Knowing how much to add isn't much good without the original spring rate obviously.


Adam, they are slightly progressive, but at the main effective rate they're rated at:

Front: 460 lbs
Rear: 680 lbs


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## 20v master (May 7, 2009)

Marcus_Aurelius said:


> Adam, they are slightly progressive, but at the main effective rate they're rated at:
> 
> Front: 460 lbs
> Rear: 680 lbs


So a 550 lb front spring and 800 lb rear spring, with perhaps an 850 lb rear going down in sway bar size to OEM R32 bar to remove some of the "solidness" of the larger rear bar I'm running now, might be the ticket. Time to experiment.


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## Marcus_Aurelius (Mar 1, 2012)

20v master said:


> So a 550 lb front spring and 800 lb rear spring, with perhaps an 850 lb rear going down in sway bar size to OEM R32 bar to remove some of the "solidness" of the larger rear bar I'm running now, might be the ticket. Time to experiment.


A 550/800 lbs combo would be sweet with no front bar and an R32 rear bar. The only thing I'd do to that combo is maybe drill new holes to the rear R32 bar to be able to dial the final balance and track behavior a bit (if needed). :beer:


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## tedgram (Jul 2, 2005)

opcorn:


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## [email protected] (May 14, 2009)

Well I figured I would give some feed back after tracking with front and rear endlinks and corner balance. The TT performed very well, providing second lap in having an "Oh crap!" moment when turning into Big Bend, the tires were not up to my normal wet line. The Hankook R-S3's are no where as good in the rain as the NT-01s. 

Ended up turning a 1:07.6 at Lime Rock yesterday. Slightly damp track. Overall other than a 996 GT3 and a C6 Z06....the TT really shines at kicking some BMW and Porsche butt! 

Last session started getting a vibration on the last lap (felt like a wheel tossed a wheel weight or picked up a good glob of rubber) Came in and was checking things over and discovered that the front left wheel bolts were coming loose. Even though I double checked the torque on the bolts after 500 miles. Since Lime Rock really pounds the front left corner, it can cause stuff on that corner to come loose. 

So I highly suggest after chatting with some other vets there that when attending a HPDE, that you check your wheels at least after the first session and before the second as brakes/hubs/wheels go through a couple heavy heat cycles. It does not hurt to check prior to heading out each time.


Prior to leaving we were checking the tightness of the fittings and hose on the newly installed Mocal...When exerting only about a couple pounds of checking force, the weld on the fitting broke on the Mocal  

So a AAA tow home and tonight I will toss a new cooler in and check everything over again. The bothersome part is that it took no energy to have the welds let go on the cooler. I cant imagine if we did not happen to lightly push on the fitting and having it give out on the next track day. 


Lesson for all to check, double check, triple check and check again. Anything that can happen, will happen when submitting a car to relentless abuse on the track. 

First lap out last year a 335i had an oil line off a freshly installed turbo come off and caused the car to catch on fire. 

Other than that, corner balanced the TT does very, very well in the dry and rain. With the pre-load removed off the sway bars I noticed the car is a lot less twitchy when transitioning from left to right and right to left turns. Next up, a re-tune and drop 100lbs of weight off the car. 

The TT really does make a great weekend track day car that can be driven to and from the track and be reasonably competitive.

:beer::beer::beer:


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## 20v master (May 7, 2009)

OEM rear sway bar is 14mm?


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## Marcus_Aurelius (Mar 1, 2012)

20v master said:


> OEM rear sway bar is 14mm?


Pretty sure it's 15 mm on all recalled and the post-recall US production cars (the US MKIV R32 is 16 mm).


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## Doooglasss (Aug 28, 2009)

My stock is 14mm


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## All_Euro (Jul 20, 2008)

DougLoBue said:


> My stock is 14mm


 I've recently bought an 01' TT225 parts car - I'll check the rear sway bar diameter tomorrow. 

Just read through this today, awesome thread!!! Funny enough, I've been negotiating with Vogtland for some MK4 FWD replacement coils that failed after warranty… the Vogtland reps have been really nice but will be charging a reduced rate for the replacements. I was going to buy something Haldex friendly but now it's clear that specific valving and spring rates are the only choice  

Thanks for saving me from an ill-informed purchase. Great info and contributions :beer:


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## Marcus_Aurelius (Mar 1, 2012)

DougLoBue said:


> My stock is 14mm


 You are correct Doug, the OEM rear bar is 14mm and the USDM R32 rear bar is 15mm. I recently switched to an R32 rear bar, drilled the new holes to make it adjustable and stiffer. As far as results from this easy mod, the car is lifting the inside rear wheel now on asphalt with the stiffest setting and I will have to move back to the softer stock setting of the R32 bar. (The car could never tripod on asphalt with the TT 14mm bar on stiff setting). 



All_Euro said:


> I've recently bought an 01' TT225 parts car - I'll check the rear sway bar diameter tomorrow.
> 
> Just read through this today, awesome thread!!! Funny enough, I've been negotiating with Vogtland for some MK4 FWD replacement coils that failed after warranty… the Vogtland reps have been really nice but will be charging a reduced rate for the replacements. I was going to buy something Haldex friendly but now it's clear that specific valving and spring rates are the only choice
> 
> Thanks for saving me from an ill-informed purchase. Great info and contributions :beer:


 You're welcome bud! :beer:


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## Marcus_Aurelius (Mar 1, 2012)

^^^ OEM TT (14mm) and R32 (15mm) comparison: 










TT bar on the right and R32 unit on the left, both bars are drilled with new holes to make them stiffer and adjustable if needed.


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## max13b2 (Jul 24, 2007)

So for a daily street driven TT 225 w/ the occasional autocross day with PSS Bilstein coilovers, what roll bar combo would you recommend? No front/R32 rear? Stock front/19mm rear, stock front/21mm rear, etc. 

BTW - on the factory PSS springs and OEM end links. 
I'm trying to complete my suspension refresh list. I know some fine tweaking will come in time but I'm looking for some suggestions for a nice starting point.


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## Marcus_Aurelius (Mar 1, 2012)

max13b2 said:


> So for a daily street driven TT 225 w/ the occasional autocross day with PSS Bilstein coilovers, what roll bar combo would you recommend? No front/R32 rear? Stock front/19mm rear, stock front/21mm rear, etc.
> 
> BTW - on the factory PSS springs and OEM end links.
> I'm trying to complete my suspension refresh list. I know some fine tweaking will come in time but I'm looking for some suggestions for a nice starting point.


 On your combo with the default PSS rate and your specific use, my suggestion is to run: 

Stock front bar and the R32 rear bar on the stiff setting (holes drilled closer to the bar centerline). If you were to become more involved with autocrossing, or go for uprated spring rates and a revalve, then I'd suggest removing the front swaybar from the equation to get rid of some unwanted understeer. :beer:


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## max13b2 (Jul 24, 2007)

Thanks! :thumbup: 

I'm surprised you said to use the R32 15mm rear with the amount of understeer inherent in these cars. Wonder why all the aftermarket bars start at 19mm and go to 25mm (that's a lot of rear bar!) 

About how far inward should I drill the holes? About an inch from center of hole to center of new hole?


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## Marcus_Aurelius (Mar 1, 2012)

max13b2 said:


> Thanks! :thumbup:
> 
> I'm surprised you said to use the R32 15mm rear with the amount of understeer inherent in these cars. Wonder why all the aftermarket bars start at 19mm and go to 25mm (that's a lot of rear bar!)
> 
> About how far inward should I drill the holes? About an inch from center of hole to center of new hole?


 Well, the rear bar adds to the overall rear wheel rate and stiffness. As a general rule (although there are many other variables in effect), more rear wheel rate and stiffness make the rear end start sliding first (before the front end). This makes the car feel like it has terminal oversteer because the rear slips first (oversteer) before the front end does (understeer). 

As discussed early in this thread, too much rear bar (or front bar for that matter) isn't a good thing. It is really a bandaid commonly used to mask other problems in a set up - ideally these bars should really be used as trim pieces since the target wheel rate can be achieved with the springs alone (doing it with the springs take away all the flaws introduced with running too much bar). The reason why all the aftermarket bars are so stiff is because they are build to mask other front end problems and give even a stock car the "feel" of having oversteer overall behavior (we all know that the front end problems are still there and the stiff rear bar just makes the rear slide before the front does). 

To touch on the inherent understeer behavior in our car, this is what I found can cure it: 

- some of it is the result of the horrible camber curve (running stiff springs or setting a good amount of static front camber compensation will take care of that). 

- some of it is not having enough roll stiffness (again stiffer springs and bar will correct this, but doing it with the bar adds other problems). 

- finally, the size of front anti-roll bar is the biggest problem and accounts for more than 50% of the understeer in these cars. In my car, at some point I modified the front OEM bar to make it softer (elongating the arms the opposite way of what is illustrated in the rear bar). The result was positive in terms of understeer, but I didn't have enough front springs at the time to keep the front roll in check and not compromise transition sharpness. I moved to a no-front-bar setup this season and I'm happy to report that understeer is a thing of the past. I have zero push without the front bar deleted, but that works with a set of 700 lbs front springs. 

The holes in the rear bar needs to be drilled as far inward as you can. There is a point where the flat portion of the arms becomes angled and you just drill a few mm before that. :beer:


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## max13b2 (Jul 24, 2007)

Is it suggested to run poly bushings in the front and rear sway bars as well? If so, whats the difference with the universal $7 Energy Suspension ones and the $40 Powerflex ones and everything in between?


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## Marcus_Aurelius (Mar 1, 2012)

max13b2 said:


> Is it suggested to run poly bushings in the front and rear sway bars as well? If so, whats the difference with the universal $7 Energy Suspension ones and the $40 Powerflex ones and everything in between?


None really! Stiffer should make a difference on paper but is negligible (at best) in the grand scheme of things. Use whatever is cheap and available to you (I'm on stock rubber and don't plan on changing them unless they fail).


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## Marcus_Aurelius (Mar 1, 2012)

*Some discoveries I made on our stock suspension!*

I had the pleasure of talking to someone super knowledgable about suspension (my kind of people) and he questioned the possible negative effects of my wheel/tire setup. He admittedly mentioned that he wasn't very familiar with the specifics of our cars besides having a generic McPherson strut design in the front. His take was that 'visually' my setup, that has the front tires sticking out so much, would have horrible scrub radius and may be a bad handling compromise even with bigger rubber and increased track. 

Well, we got into it and he quickly learned that I wasn't totally doing things by the "bigger is better" philosophy, and that I was equally as knowledgable as he was. To begin, I confessed that the only thing I didn't get to do yet for the chassis was calculating and comparing the scrub radius between stock and my track combo (I told him that I will get back to him with some results). However, I assured him that there is no way that the wider track and increased rubber wasn't enough to compensate for any possible disadvantage there was from having so much positive scrub radius. My argument was that the increased front track helped greatly with Lateral Load Transfer Distribution (LLTD) and increased grip on the heavily loaded outside front tire in a turn. LLTD is reduced with a wider front (or rear) track and helps with load spikes that usually concentrate on the outer edge of the tires independently of the camber curve. Additionally, I also explained to him that the low front offset was also a necessary evil in order to mount fat wheels and rubber without contacting the strut (inner front clearance obviously isn't a strong point in the platform). The ability to have more meat and better LLTD was the case I made and we agreed at the end that without knowing the actual scrub values, it "should" be enough to overcome the possible disadvantage of having too much scrub (outside wheel toe-ing out under dynamic loads and compression). 

For those that aren't familiar with the concept, scrub radii are calculated from finding the difference at the ground plane between steering inclination angle (SAI) and the tire center line. It could be Zero (zero or even scrub) and friction is at the center of the tire and equally distributed across the tire contact patch - Positive, where the friction is centered somewhere towards the inner half of the tire - Negative, where friction is centered and scrubbing the outer half of the tire. Quickly explained, zero scrub is desired in most situations (99% of the audience here), while positive and negative scrub having detrimental effects on handing with all else equal. However, there are other things in effect here. We simply don't know if the Audi had designed "compliance understeer" in the car's steering, 

By now, you're probably asking yourself, what do we have stock and what are the effects of the inherent design from Audi. Well, since I'm not the kind leave rocks unturned, I got to it to so I can have an idea of what I'm dealing with and what kind of compromise I could be making in my car.

- First thing I did was to find out if the steering system was engineered for "compliance understeer" where the outside front wheel toes-out when cornering. As expected, the design is set for compliance understeer because the steering box is placed in a quadrant behind and above the center of the hub. This means that having positive scrub (low positive offset value like I have) will make things worse handling-wise by giving even more dynamic toe out to a car with compliance understeer built into it. 

- I then calculated the front scrub radius in stock form using factory fat fives with and 245 rubber on them. According to what I found out we DO NOT have zero scrub built into the design. Instead, VW/Audi built some Negative scrub into the geometry. I don't know why they would want to do that, except for space restrictions or wanting super conservative steering feel (no feel and kickback under acceleration or braking while cornering - think opposite of most communicative sport car because even some mini vans have at least zero or positive scrub in their design). 

As you can see the stock scrub is a bit negative and the contact patch is scrubbing and more loaded towards the inner half of the thread width (scrub point is offset substantially from inner wheel barrel and still off-center at the ground point)





- Finally, I also calculated the amount of scrub in my race combo. Somehow, I lucked out on almost Zero scrub without even trying. I calculated that moving my wheel setup another 2mm will put me right at the magic 0 mark, but I'm not going to loose sleep over it. The scrub is close-to-perfect enough to not warrant any changes, especially when stock is inherently horribly located in terms of performance.


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## warranty225cpe (Dec 3, 2008)

Pretty cool Max :beer:


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## Neb (Jan 25, 2005)

So to wrap my head around this, could you not adjust the scrub by adding more +- camber? And if so could you adjust your 'stock'/track setup on the fly if you had top mount camber plates?


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## warranty225cpe (Dec 3, 2008)

Neb said:


> So to wrap my head around this, could you not adjust the scrub by adding more +- camber? And if so could you adjust your 'stock'/track setup on the fly if you had top mount camber plates?


Almost sounds like spacing would affect it more so than camber. I could be (probably am) wrong.


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## Rod Ratio (Jun 6, 2012)

Always learning something from this guy :beer:opcorn:


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## warranty225cpe (Dec 3, 2008)

Rod Ratio said:


> Always learning something from this guy :beer:opcorn:


Nice to see you slumming homie :beer:


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## TheDeckMan (Sep 26, 2004)

warranty225cpe said:


> Almost sounds like spacing would affect it more so than camber. I could be (probably am) wrong.


Bigger the spacer, the worse it would be.


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## Marcus_Aurelius (Mar 1, 2012)

Neb said:


> So to wrap my head around this, could you not adjust the scrub by adding more +- camber? And if so could you adjust your 'stock'/track setup on the fly if you had top mount camber plates?





warranty225cpe said:


> Almost sounds like spacing would affect it more so than camber. I could be (probably am) wrong.


Correct, the final offset (spacing or wheel offset) is what will have meaningful impact on the amount of scrub radius. The steering angle inclination SAI (virtual line drawn between the strut upper center mount and the ball-joint mounting point at the hub) is potentially altered by camber changes depending on the geometry. However, with our specific design, adding camber at the top (changes above the center of the hub) is compensated almost equally by the lateral distance changed at the bottom (under the center of the hub). Same thing happens if the camber is added by ball joint spacing (like I do) at the bottom. So, negligible changes with camber and very drastic changes with offset alterations.


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## Rod Ratio (Jun 6, 2012)

warranty225cpe said:


> Nice to see you slumming homie :beer:


Eh, it's all about 'get in, where you fit in'; right mang? :wave:


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## 20v master (May 7, 2009)

Marcus_Aurelius said:


> A 550/800 lbs combo would be sweet with no front bar and an R32 rear bar. The only thing I'd do to that combo is maybe drill new holes to the rear R32 bar to be able to dial the final balance and track behavior a bit (if needed). :beer:


So the V3's I'm trying to sell also have a set of Eibach linear 500/800lbs springs that Chris bought to run with the KW shocks. Hmmmm.....


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## Marcus_Aurelius (Mar 1, 2012)

20v master said:


> So the V3's I'm trying to sell also have a set of Eibach linear 500/800lbs springs that Chris bought to run with the KW shocks. Hmmmm.....


That's a sweet setup, I wonder how Chris landed on this well thought out linear spring combo...


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## 20v master (May 7, 2009)

Marcus_Aurelius said:


> That's a sweet setup, I wonder how Chris landed on this well thought out linear spring combo...


Gee, I wonder....., but did he get the shocks dyno'ed to know what the V3's can take spring wise? Plus, they're double adjustable, which means inherent cross talk, so there's no way to know what they are set at currently. It is nice to know he didn't just "go stiffer" with springs though.  There is ANOTHER set of springs that were on the fronts when we got them, they're a different color than the Eibach's and the KW springs. :screwy:


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## Marcus_Aurelius (Mar 1, 2012)

20v master said:


> Gee, I wonder....., but did he get the shocks dyno'ed to know what the V3's can take spring wise? Plus, they're double adjustable, which means inherent cross talk, so there's no way to know what they are set at currently. It is nice to know he didn't just "go stiffer" with springs though.  There is ANOTHER set of springs that were on the fronts when we got them, they're a different color than the Eibach's and the KW springs. :screwy:


IIRC, their curves, while not the most impressive, aren't as narrow as some of the other useless offerings, and with default valving shims supposedly can accept up 900 lbs of springs without needing a revalve (information not based on empirical knowledge since I never had a set dynoed personally).

As far as the amount of crosstalk inherent to the specific V3 default valving, I can't comment without the dyno data. What I know is that most entry level double adjustables have horrible crosstalk, and you have to move to expensive exotic offerings before having the feature without too much of the side effect bundled in there. Why aren't you using them (although we know a revalved set of Bilstein inverted monos are a better proposition to most)?


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## 20v master (May 7, 2009)

Marcus_Aurelius said:


> IIRC, their curves, while not the most impressive, aren't as narrow as some of the other useless offerings, and with default valving shims supposedly can accept up 900 lbs of springs without needing a revalve (information not based on empirical knowledge since I never had a set dynoed personally).
> 
> As far as the amount of crosstalk inherent to the specific V3 default valving, I can't comment without the dyno data. What I know is that most entry level double adjustables have horrible crosstalk, and you have to move to expensive exotic offerings before having the feature without too much of the side effect bundled in there. Why aren't you using them (although we know a revalved set of Bilstein inverted monos are a better proposition to most)?


Trying to sell the V3's as is to buy RSS's, but could use the extra springs on my PSS's.


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## Marcus_Aurelius (Mar 1, 2012)

20v master said:


> Trying to sell the V3's as is to buy RSS's, but could use the extra springs on my PSS's.


Good man! RSS's are really amazing on a purpose car (even with default valving and spring rates). :thumbup::thumbup:


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## Rford71 (Sep 1, 2011)

Great thread more information then I can't personally comprehend.:thumbup:

I plan on doing a couple of track events this year for the first time and would like to make some improvement to my suspension on my 04 3.2l. The only suspension mods I have done our Vogtland hight adjustable coilovers, Autotech 22mm hollow swaybar (after reading this thread I guess I should go back to stock swaybar) and two sets of adjustable control arms in the rear. Being this is not going to be a track purpose car I was thinking of going with some PSS9 or something I can adjust on-the-fly. 

Would anyone know if I could run a slightly stiffer spring upfront on the PSS9s with out having them re-valved due to that extra weight of the I have from 3.2 L engine?

Also my car is lowered some, not slammed and I was interested in getting the H2sprot spindles, but apparently they are not making them any more. What do you guys think about the USRT's Roll Center/Bumpsteer Correction Kit(not for sell yet), do you feel they would be beneficial?

http://www.usrallyteam.com/index.php?main_page=product_info&cPath=76_182_222&products_id=1856


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## Marcus_Aurelius (Mar 1, 2012)

Robert, you'll really get to enjoy the car and all the work you've done to it by taking it to the track. 

Ideal setup IMO (since you are mostly street with occasional track) would be a set of PSS/PSS9 on modified stock or R32 rear antiroll bars. This combo is very well balanced, and even better if the front antiroll bar is disconnected or removed while tracking. I have recommended it to many, along with a good performance-oriented alignment, and everyone reports great handling but most importantly balance while at the track. I keep mentioning balance because this is what makes or break a good-handling track car (even if not the fastest or wild setup, it allows the driver to push hard confidently without battling the car). 

As you may have picked up by now, I'm not a big fan of too big or aggressive rear antiroll bars when paired with properly sprung coilovers. They make the TT/R32 prone to tripoding at the limit and a bit too loose in fast cornering. These things may feel somewhat good in the street but what they do to the balance when the car is really pushed is not desirable. I can see their need with stock or inappropriately sprung coilovers, but stay away if your upgrading to a solid coilover like the PSS/PSS9 (btw, I feel the PSS is better since it doesn't allow you mess with and possibly screw up an otherwise great set of coils). 

As as far as roll center correction (uprated spindle or other form of geometry alteration), you can't go wrong especially if the car is lowered. As you know the H2sport spindles are history because they stop making them ages ago. The roll center correction kit I'm making is still in the works and not ready for release. Scott had the original 2-piece kit posted, but the final version is a one-piece extended ball joint with matching extended rod end to eliminate unwanted bump steer that results from changing static roll center location. 

Let me know if you have more questions and I'll gladly answer them. :beer:


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## racin2redline (Sep 25, 2008)

Can we make this thread a sticky?


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## Marcus_Aurelius (Mar 1, 2012)

racin2redline said:


> Can we make this thread a sticky?


That would be helpful for those in the community that care about suspension - and definitely motivate me to post more stuff in this thread besides just answering questions (I pretty much abandoned it after my Madmax moniker was sent to the deep end). It would be cool too, since we have James as a real moderator now , if post #4 could be re-opened just so I can write/finish my original posts on the platform's suspension.


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## Rford71 (Sep 1, 2011)

Thanks Max, do you know if the PSS and the PSS9's use the same spring rate of Front: 460 lbs Rear: 680 lbs? I'm assuming a slightly stiffer spring up front 550lbs would help me with the heavier 3.2 motor. Also do you know of a front camber kit that works with the PSS9's? I think I remember reading that the GC's didn't work with Bilstein.

I just measured my stock rear sway bar, it is 16mm which appears to be 1mm thick or thin the R32. I guess that may be because the TT has a shorter wheelbase than the R32 according to Edmunds TT WHEEL BASE 7 ft. 11.6 in. (95.6 in.) R32 WHEEL BASE8 ft. 3.1 in. (99.1 in.)


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## reflexgti (Dec 19, 2000)

Bilstein has a specific fitment for the R32 that should have already factored in the additional weight of the R32 vs the TT. As for our GC camber plates, they will fit all of the Bilstein coilovers for the MK4 platform.

Thanks,
Steve


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## Rford71 (Sep 1, 2011)

reflexgti said:


> Bilstein has a specific fitment for the R32 that should have already factored in the additional weight of the R32 vs the TT. As for our GC camber plates, they will fit all of the Bilstein coilovers for the MK4 platform.
> 
> Thanks,
> Steve


Steve, 
Thanks for the information on the ground control camber kit. But my questions about the PSS9's and spring rate are for my fellow TT owners that track there vehicles. 

Bilstein uses the same PSS9 kit for TT 1.8T, TT 3.2 and R32, part number is GM5-8042-HO. Bilstein DON'T have specific fitment for factored in the additional weight.


Robert


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## max13b2 (Jul 24, 2007)

Marcus_Aurelius said:


> if post #4 could be re-opened just so I can write/finish my original posts on the platform's suspension.


^^This! :thumbup:
I have really missed the technical threads by Max.


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## TT_CS (Nov 26, 2013)

*Query on the scrub radius of a stock TT*

Hi,

Firstly thank you for taking the time to present your findings with respect to the TT's suspension

Just trying to digest a few things from this thread, namely in your first post what you term as NSRR, Negative Steering Roll Radius, from your description:

"NSRR can be understood by drawing an imaginary line down through the ball joints when looking at the car from the front. The point where that imaginary line hits the ground is said to be negative if it lands outside the tire’s centerline (like in the TT)."

By 'outsisde' I assume you mean away from the cars centreline and towards the outer edge of the tyre / car?

Somewhat later on page 5 in a post titled "Some discoveries I made on our stock suspension!" you show a practical exercise whereby the tyre contact print bears 'witness marks' from having been steered whilst in contact with the ground in order to show the point about which the tyres contact print appears to have been steered



The tyre is marked In & Out and what appears to have been marked as the contact patch pivot centre, this centre is shown as being toward the inner edge of the tyre, you still refer to this as negative scrub but now hits the ground 'inside' the tyres centreline?

I have probably misinterpreted what you have said and I do not have the suspension / hard points of the TT suspension so cannot sketch it out to try and clarify this to myself.

My understanding of negative and positive scrub radii are as per the Googled image below which I believe from your first post is the same as your understanding



Does your practical test not show positive scrub radius for the stock suspension that you tested 

Cheers


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## Marcus_Aurelius (Mar 1, 2012)

^^^ thanks for posting and engaging in a technical thread that we can all benefit from. :beer:

To answer your first question, by 'outside' my definition meant 'away from the tire's centerline' and 'towards the outer edge of the tire/car'. This is in-line with the google and other definitions of Scrub Radius or Steering Roll Radius. 

What made my post on page 5 off, now that I'm thinking about it, are my alterations to camber by relocation of the ball joint pivot points outside of where the are from the factory. This unusual way of gaining static negative camber compensation (via custom BJ relocating plates) definitely had an effect and moved the steering roll radius toward 'positive' and wasn't factored in my post. I will re-test for it and revise my post entirely when I have the car back on the ground from turbo surgery. As you have pointed, and answering your second question, the practice tire demonstration pics showed positive scrub radius on my altered and not really 'factory' setup. It escaped me to make the connection as I was more focussing on the changes that my race wheel/tire combo offset/width potentially had on the steering and suspension geometry. Good catch btw and thanks for mentioning, I usually post these things and rarely get to back and re-read my posts, so it's great to have people not just skimming over the content posted. Keep posting, people like you are a dying breed on this forum and it's refreshing to have you aboard. :beer:


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## reflexgti (Dec 19, 2000)

Rford71 said:


> Steve,
> Thanks for the information on the ground control camber kit. But my questions about the PSS9's and spring rate are for my fellow TT owners that track there vehicles.
> 
> Bilstein uses the same PSS9 kit for TT 1.8T, TT 3.2 and R32, part number is GM5-8042-HO. Bilstein DON'T have specific fitment for factored in the additional weight.
> ...


IIRC, back in the day, Bilstein had two different applications for the Audi TTQ and the Golf R32 though I might be wrong as it's been awhile.


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## TT_CS (Nov 26, 2013)

*Why am I interested in if the TT has negative, ground level, lateral offset?*

Firstly I apologise if I laboured the point about whether it was negative or positive and it's definition but I find that the sign convention (or lack of) is often a source of confusion in discussing things like this, so I just wanted to make sure we were aligned.

In fact it was your reference to 'NSRR' in your first post that really drew my attention, (I had not previously heard of this as a name for 'it' - negative scrub radius, negative kingpin offset, negative ground level lateral offset etc...) 

But it was not your use of an unfamiliar name that I am referring to but the fact that the TT had (I will use the term I am familiar with  ) negative, ground level, lateral offset 'NSRR'...

Infact I am so used to looking at just the magnitude of this offset and not it's sign that I had to look back through any data I had to remind myself that all of the data I have from various vehicles all exclusively have POSITIVE, ground level, lateral offset.

So I was particularly interested to know if you had deduced this from a kinematic model you created or if it came from published paper or data from Audi?

So why was I interested in this? I've done close on 40,000 miles in my TT 225 Coupe and even though the TT steering seems to be an area which provokes some negative comment an aspect of it that I particularly like is the lack of what I call 'steering corruption'. This regularly tends to be lumped under the banner of 'Torque Steer' but basically any torque fed back to the hand wheel not associated with say any genuine cornering or braking and / or a nett vehicle steer that I didn't request from the car. 

The TT like many 4WD / AWD vehicles is FWD until it becomes traction limited (In the specific instance I am interested in) and then with a finite delay becomes 4WD, so it is potentially just as likely to be affected by 'steering corruption' as a FWD car at least in the first part of a manoeuvre / traction event.

I have driven many 'high' powered FWD vehicles with varying degrees of steering corruption but the TT stands out as being very well behaved in this aspect, so either:

1.) The TT 4WD always 'wakes up' quickly enough and without me noticing it's intervention (No ESP light activity on dash - not sure if a pure traction intervention from either the ESP / Haldex controller will cause this to light up?) so that all four wheels share the available torque - meaning the 4WD is active more often than I (we) give it credit for?

2.) The TT steering geometry does a good job of 'filtering' out this unwanted corruption (Some may argue that this could contribute to a lack of 'feel' depending on how it's done) 

Hence I began to wonder if the TT was the first car I have used which has a negative, ground level, lateral offset and if this was relevant / significant?

Incidentally I keep referring to scrub radius / lateral ground level offset and the steering torque generated by it, it is in fact the HUB level lateral offset that is responsible for the torques felt in the hand wheel during acceleration and the GROUND level lateral offset which generates the torques felt in the hand wheel during braking, but most of the things we can change readily such as wheel offset / spacers effect both by a similar magnitude.

Sorry my response is a bit 'wordy' just trying to explain my interest.

Cheers


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## TT_CS (Nov 26, 2013)

*Lets talk rear damping characteristics - TT 8N Quattro*

In the interests of discussing things in the correct forum 

Following on from a previous discussion...

One of biggest criticism of my Quattro 8N TT, it doesn't deal with uneven road surfaces very well, this can be at either relatively low vehicle speeds or indeed higher vehicle speeds, also I don't mean 'off road' just poorly maintained roads. This is especially bad for things like pot holes but I am just talking about 'uneven' surfaces. 

Independent of me thinking this Marcus also stated:



Marcus_Aurelius; said:


> One thing that caught my attention as well with the stock suspension was how easily unsettled it gets in the back over rough surfaces. Knowing how low the spring rates and resulting Natural Frequencies are, only two possible things are making this happen (maybe it's a combination of both):


One possible area of investigation for this problem is the rear damping characteristics, specifically the 'percentage critical damping' and how that value changes throughout the usable damper velocity range. 

Although not yet backed up with hard data yet the TT 8N Quattro seems to have a ride frequency of around 1.7 - 1.6 Hz at the front and 1.6 - 1.5 Hz at the rear which is not a particularly high value for ride frequency and means that as far as the coil spring contribution is concerned it is unlikely that it is responsible for the TT 8N Quattro's inability (IMO) to deal with less than perfect road surfaces.



Marcus_Aurelius; said:


> a) The valving on the dampers, specifically what's controlling the high velocity forces (commonly referred to as high speed valving). Whenever I had a damper (although all my experience is in motorsport conditions) that struggled to properly control rough surfaces, it always was a result of overdamping of the high speed valving for the specific Natural Frequency used. Fixing this region of the valving always took care of this problem for me and I'm sure plays a role in what is happening with the TT's odd behavior in stock form. Generally, staying under 0.5 critically damped above 4 in/sec of shock velocity is a good place to start.



I'm not sure I can tell if what I feel should fall in to the category of low or high speed damping (or indeed both, but that's not important yet) I understand it is likely to be in the higher velocity area but I don't want to rule out the 'transition' velocity area between what people think of as low and high speed damper velocities, what I want to do is understand what the damping characteristics of the standard car are - as that is the car I have driven for the last two years and is the basis of my perception.

In order for me to understand the standard car a little better (starting with the rear first) I believe I need to know:

*Rear coil spring rates* - I will measure these soon but current estimates are between 50 - 60 N/mm
*Rear coil spring motion ratio* - Happy to use 0.63 for this
*Parasitic contribution* to overall wheel rate from suspension bushings - Beyond the scope of this exercise without data for each bush or a Kinematics and Compliance test rig
*Rear Bump rubber / 'spring aid' *- it's point of contact and the additional wheel rate it gives, easy to determine point of contact but not so easy the rate characteristics 
*Rear cornerweights* - known
*Rear unsprung mass* - pretty easy to estimate the values I haven't actually weighed yet which make this up
*Rear damper force / velocity characteristics* - I will try and get one of my units measured but likely to be lower than when new - but still representative of what I feel now
*Rear damper motion ratio* - How much the damper moves relative to the wheel vertical motion I will try again to measure

Marcus I am not sure what you meant when you said: (Specifically the bit where you say 'depending on the one that is used'?



Marcus_Aurelius; said:


> Damper motion ratio is going to vary depending on the on the one that is used. That's why it is mostly left out in general suspension tuning as it's a constant variable. Imo, there is no need to calculate or even worry about it at this level, just make sure the dampers are critically damped and valved properly for the intended use and chosen spring rates.


Do you mean don't worry about any non linearity? Not sure what you mean when you say i_t depends on the one that is used_, when I have a non linear motion ratio I always use the motion ratio that is given with the car at my chosen nominal ride height (so if it were say 0.5 at my nominal ride height and fell to 0.4 at full bump I would still use 0.5 for my initial calculations, perhaps checking at 0.4 to see how much it differs)

Without knowing the damper motion ratio it is not possible to work out the percentage critical damping that the standard set up has. The angle of the damper on a TT means it is almost certainly not a constant motion ratio. Also do we agree it is almost certainly not 0.63 i.e. the same as the spring motion ratio?

You say make sure the dampers are 'critically damped' do you mean that? Whilst damping can be at or above critical damping in the low damper velocity region (say below 100mm/sec, 4 inches/sec) it is almost always well below 'critically damped' (50% or less) above this damper velocity for a road car. well indeed for any race car (bar one) I have been involved in too. You stated (and I agree with) below 50% critical damping from about 100mm/sec (4 inches/sec) is a sensible start and if the standard TT characteristics are below this then I would tend to think that over damping is not the cause of the poor rough surface behaviour of the rear axle.

So I basically need to know both the rear damper motion ratio and the rear damper force velocity characteristics up to say 0.5 metres/sec (20 inches/sec)


Any thoughts on this as a plan or any data to help fill in the gaps? Especially rear damper motion ratio, do you have a value that you have used or measured? 

Cheers


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## Marcus_Aurelius (Mar 1, 2012)

Before we get started I have some questions for you, are going to re-valve OEM dampers or are you're going with aftermarket ones and have them valve to your chosen spring rate? Are you re-valving them yourself? 


Let's start with what we know (assuming the problem is only a result of damper valving and not a combination of things): 


- The problem is mostly and more pronounced in the rear. Therefore that's where we should focus the discussion towards. 


- 1-3 in/sec is the normal range of chassis lean (a bit of a generalization and likely to be in the 1-2 in/sec, but usable when we don't have real means of specifically testing for it for our platform). Therefore we can speculate that what we have both experienced with the stock suspension is happening at least at a higher shock velocity range (say 4 in/sec and up). To keep things simple, I usually refer to this valving region as "high speed" (blending the mid-range 3-8 in/sec and high velocity 8-up in/sec regions together). Therefore, I see where you may be concerned with some of the problem falling in the 'knee speed' or transitional region of the damper's valving (say 3-5 in/sec ). But as you probably know, knee speed may not be easily tunable on most low end shocks due to valving design limitations (One of the reasons I asked what shocks you plan on using). 


So, if you're focussing on the stock damper valving to find the root of our stock-suspension problem, I understand why you you'd want to shock motion ratio to be known. However, the problem I have with relying on damper motion ratio to fix transient problems for our type of suspension is that it's not linear throughout the range of travel. Relying too much on the shock motion in your calculations (say at stock ride height) has the potential of giving you some value that may not correlate to where the problem you're targeting to fix is happening. From my observations (going by memory because I haven't been on stock suspension for years), the unsettling behavior happens with some chassis lean or roll angle to be more exact (inside shock droop, outside shock compression). The real effective way IMO to use the shock's motion ratio for what you're trying to fix would entails knowing when in the travel range the issue arises, and calculating the motion ratio for that region of the shock's travel. To give you a ballpark reference, when I had my rear coilovers valved I had to come up with some correction factor to account for the angle and motion ratio that was not at 1:1 like it is on the shock dyno. I think I estimated and used 0.9:1 - the lower shock mount is almost at the wheel (say 0.97-0.98) and the rest of 0.1 offset grossly accounts for the shock angle which is about 10 degree IIRC. 


With that said, if you want to use the damper motion ratio it should be easily calculable, and you're correct, it's definitely has nothing to do with the spring motion ratio in our rear design because we don't have a coil-over-spring design. Since my car is already on stands, maybe I should tackle the measurement (involves removing the rear spring and measuring the difference between shock and wheel travel in both directions from a chosen ride height). Problem now is it's super cold, so we'll see when I can get to it, but I'm intrigued. 


- When I said to not worry too much about it and that it depends on the damper used, I was referring to the type of valving used. The effect of motion ratio at the wheel (used to reference the characteristics of the valving curves) is mostly proportional to the damper motion ratio squared for non linearly valved shocks, and mostly proportional to the spring motion ratio squared when using valving curves that are linear in each phase of the valving. Most good aftermarket systems use linearly ramping curves in each phase of the valving, therefore you're better served using the spring motion ratio as your reference. Again this brings me to the question of what damper you will use (I've never dynoed a stock damper so I'm not sure of what to expect). 


- The rear spring motion ratio of 0.63 proposed by 20vMaster is correct and you can use it with confidence. By critically damped in the valving I meant spec-ing your valving to not over/under shoot the chosen factor (obviously for each region of each curves) for your known chassis calculations (which includes sprung and unsprung weight, chosen ride frequency and wheel rates, motion ratio etc.). Say you decide, after gathering all your data, you're going to custom valve your dampers at .65 in low speed and 0.4 in the rest of the higher velocity range, you normally shoot to stay true for these values or factors of being critically damped (one cycle per deflection and using a hypothetical factor of 1) throughout each region of the curves. 



PS: I know you grasp all this already, but I have to keep the rest of the audience in mind so it's not a dialogue that's irrelevant to the rest of the readers. BTW, it's refreshing to have this kind of conversation in our TT forum that is understandably seen by many as lacking technical substance.


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## TT_CS (Nov 26, 2013)

I hadn't even considered revalving the standard units as an option, Whilst I haven't specifically looked closely at the TT rear dampers in my experience OEM units are almost always crimped / swaged ends to the damper body which renders them to all intents and purposes as unservicable units. And even if you can get them apart getting hold of the correct shims / pistons etc can be a challenge - so no my plan was to use 'aftermarket' units which I can easily get revalved.

The following is not a declaration of correctness or the right way to do anything it simply my method of working, the problem with internet discussion is that it can quickly sound like criticism but please regard this as healthy debate and no more than that  

Damper motion ratio:




Marcus_Aurelius; said:


> However, the problem I have with relying on damper motion ratio to fix transient problems for our type of suspension is that it's not linear throughout the range of travel. Relying too much on the shock motion in your calculations (say at stock ride height) has the potential of giving you some value that may not correlate to where the problem you're targeting to fix is happening.


I'm not relying on the damper motion ratio to fix anything, I just need to know it's characteristic, as I mentioned in my previous post I may start with a nominal damper motion ratio at my chosen ride height I will then go on and recalculate the percentage critical damping based on the worst case damper motion ratio to see how much that differs from what I initially had.

It could simply be a difference on our 'workflow' - which is perfectly acceptable as people do work differently, but without physically measuring the rear damper motion ratio we don't know how non linear it is do we? - so whether we think we should use it or not we need to go through the process of measuring it. 

I would still always use the motion ratio data and then go on and calculate the percentage critical damping throughout the damper velocity range, this is how I have done every vehicle I have ever worked on and then used this as a start point for the damper curve. I have a variety of percentage critical damping characteristics that I am comfortable with and how they behave and it should give me an idea where the TT fits in with these.

I guess most vehicles I have had motion ratio data for have been reasonably constant so the issue of any non linearity hasn't been significant. 

The alternative is?.... I measure the rear damper force / velocity for the OEM units and then make something a bit softer or a bit harder and see which direction feels right? I prefer to measure the damper force / velocity characteristics of the TT - see if it seems over or under damped based on the calculated percentage critical damping it has and if necessary I will do this for a few values of motion ratio to see how much this changes - and then see how I change or scale the damper curve.

If you could measure the motion ratio that would be fantastic, I don't have access to a workshop or a flat dry area at the moment (well not one that I can put my own private car in anyway) Whereas I have relatively good access to a fully hydraulic damper dyno for damper and spring measurements as required. I asked on another forum (UK) if anyone had springs / dampers of any origin (for a TT) so I could build up a bit of a database but got no joy - so I will have to take my own car out of commission and / or wait until I have replacement items to test them. 

To give people some idea of what we are talking about as far as Critical damping characteristics as a function of damper velocity: below is an example for a fairly soft European 'shopping' spec car.



Cheers


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## fabric8 (Jul 4, 2000)

*Input needed*

I stumbled upon this thread in search of finding information to help me figure out a problem I'm having with my TT's suspension/chassis. This thread is a wealth of information about the TT's suspension, and rather than sidetrack this thread with my situation, I'm posting a link to mine hoping the knowledgeable folks can shed some light to it:

http://forums.vwvortex.com/showthread.php?6916147-Suspension-guru-s-invited-to-help-solve-this-problem[/URL]


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## Late__Apex (Dec 2, 2007)

TT_CS said:


> The alternative is?.... I measure the rear damper force / velocity for the OEM units and then make something a bit softer or a bit harder and see which direction feels right? I prefer to measure the damper force / velocity characteristics of the TT - see if it seems over or under damped based on the calculated percentage critical damping it has and if necessary I will do this for a few values of motion ratio to see how much this changes - and then see how I change or scale the damper curve.


I may not grasp the minutia of shock tuning, but I feel I may have something to contribute, so here goes.

From my perspective (competition driver with a fair bit of suspension knowledge) it seems like you are trying too hard to perfect non-adjustable suspension components. To me, the problem lies in the motion ration of the spring, not the shock, but the motion ratio is a constant, not a variable. The solution is obvious - get a set of (even mildly) adjustable dampers in there and you will be able to find a setting that suits your [tires, driving style, level of aggression, road conditions, weather]. Pick one. 

If you were an engineer for Audi Sport, H&R or Bilstein I could understand your interest. The fact is that you could set up the "perfect" suspension setup for you and it would not work perfectly (or maybe not even acceptably) for for me, or Max, or Tom Kristensen, or Seb Vettel. All race cars have some aspects that are fixed and some that are variable. That's the fun part, no?

To paraphrase the 12-steppers: Help me accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference.


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## Marcus_Aurelius (Mar 1, 2012)

TT_CS said:


> If you could measure the motion ratio that would be fantastic
> 
> Cheers


I took some measurements for you to figure out the rear damper vs wheel ratio. Each inch of wheel travel is equivalent to 0.8" of damper travel in both directions. 

*-Compression* (starting at static ride height)

1st inch of wheel travel = 0.8" of damper travel
2nd inch of wheel travel = 0.8" of damper travel

*-Rebound* (also starting from ride height)

1st inch of wheel travel = 0.8" of damper travel
2nd inch of wheel travel = 0.79" of damper travel

(*I think that the second inch of wheel travel in rebound, basically at full droop, there is some slight bushing resistance and that's why I got 0.79" of damper travel which is negligible IMO and was rounded to 0.8")

*-Other data collected *(this purely for my setup)

Effective range of wheel travel 4"
Effective range of damper travel 3.2"
Total range of wheel travel 5"
Total range of damper travel 4"




*
Full range of shock travel from full droop to sitting on my chopped bump stops. For those who care, it's only 3.9" (10 cm) total, which is less than 2" total of compression travel at my current height. I can only imagine what's going on with more lowered cars on softer springs (basically how the majority on this board runs) *

























*
Crude marking on the damper after each inch of wheel travel (Rebound and compression starting from my static ride height). Each inch of wheel travel is equivalent to about 0.8" of damper travel in both direction and that's what the marking illustrated. *


















*
This pic shows what I did to get a fixed point near the center of the hub that can be measured at a 90* angle (necessary since the rear hub is so inboard of the wheel arch). You can also spot on the left the small amount of total damper travel available overall (compression and rebound). 
*

















*
Random pic showing full bump/compression and the frame resting on the chopped bump stop. If you're lowered a lot, especially on soft spring rate (anything lower than 900 lbs is soft IMO - I run 1300 lbs on my car), chances are you're riding on the bump stop and the effective rate is a gazillion lbs (not good). 
*












*





Pic below shows how wheel travel was measured from static ride height*


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## 20v master (May 7, 2009)

Marcus_Aurelius said:


> I can only imagine what's going on with more lowered cars on softer springs (basically how the majority on this board runs) [/B]


Don't forget to throw in the super stiff rear swaybar too. :laugh: Great post Max. :beer:


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## max13b2 (Jul 24, 2007)

Anyone know the effective spring rate of the Bilstein PSS coilovers? As I understand they are progressive but the only data I could find is 
460lb - front 
680lb - rear

This seems pretty soft so I'm not sure how accurate it is.


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## 20v master (May 7, 2009)

max13b2 said:


> Anyone know the effective spring rate of the Bilstein PSS coilovers? As I understand they are progressive but the only data I could find is
> 460lb - front
> 680lb - rear
> 
> This seems pretty soft so I'm not sure how accurate it is.


It's accurate.


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## TT_CS (Nov 26, 2013)

That's fantastic Max thank you,

I was considering doing this when I changed the springs / set up my rear lateral links if you hadn't had chance to do it - but no need now, cheers

I just need to juggle getting one of my rear dampers off the car to get the FV measured and then see what sort of % critical damping the standard car has as a start point

Then I can look at getting some dampers valved depending on the findings

Cheers


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## Marcus_Aurelius (Mar 1, 2012)

20v master said:


> Don't forget to throw in the super stiff rear swaybar too. :laugh: Great post Max. :beer:


I've been seriously considering doing a real coilover conversion for that exact reason (now that it's legal in my SCCA class). This would allow me to run completely sans-swaybar without having to go too high in rear spring rates. With a true coilover conversion, 600-700 lbs springs would be enough to give me similar wheel rate as I'm getting with 1300 lbs rear springs in the OEM inboard location with 0.63 motion ratio - but the big advantage is no sway and the possibility to run a 7" stroke shock (much more droop travel) in the process. I really want some Penske or JRZ but the price is hard to swallow, maybe I can score a used set of koni 28 series in an acceptable stroke and get that done for this spring.


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## andrew1984 (Jun 24, 2002)

Marcus, im with you. I'd like something like that for my R32 as well.


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## All_Euro (Jul 20, 2008)

Anyone have, of know of, any experience with these... http://www.hypercoils.com/bellows-springs.html#.U0dalF5U2f0 , http://www.hypercoils.com/PDF/Carbon-Composite_Bellows_Springs.pdf

Love the theory of them...


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## Marcus_Aurelius (Mar 1, 2012)

Very interesting concept! I do not have any experience with them, so I can't say. The only thing is this will most likely not work in the rear of a Quattro with a non-coilover design. Being curious, I may try a set of 800 lbs in the front to see how they measure against the old reliable spring design (don't have an issue with natural side loading and spring bind since I'm using inverted monos).


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## tedgram (Jul 2, 2005)

Interesting from weight saving standpoint.


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## Billtt32 (Jun 18, 2013)

It's new suspension time. She has 224k on her, shocks springs are getting tired. 

Just installed 4 new AS3 tires today. 

I like the car's ride now. I don't like the heavy front end feeling into curves. This will not be a track car. I do drive it fast in the mountains etc etc. 

After studying this thread many times..Here is my goals

1: Stay as close to stock as possible
2: Lower the car around 1" MAX
3: Find a thinner front sway bar (or modify the stock one) 
4: Smaller rear sway (or modify the org)
5: New shocks
6: New springs
Revamp all the rubber parts relating to suspension. 

So how would you do it? What products etc?

MAX? I will be ordering some defcon stuff soon. Please suggest the perfect setup for a street, canyon carving, car? Best sways to get, or mod the org's? Thxs


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## Billtt32 (Jun 18, 2013)

Up for ideas on what suspension i should install. \

What is everyone using, pros and cons of each?


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## TheDeckMan (Sep 26, 2004)

Billtt32 said:


> Up for ideas on what suspension i should install. \
> 
> What is everyone using, pros and cons of each?



What are you doing with the car?

Depends on what your looking for. I am a big H&R guy due to having run them for 10+ years without a single problem. From street to track they are the some of the best riding and handling coils on the market. Driven a lot of KW and Koni setups, personally only had one good experience with Koni and that was a full custom setup that was dyno'd to the car.


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## Billtt32 (Jun 18, 2013)

DeckManDubs said:


> What are you doing with the car?
> 
> Depends on what your looking for. I am a big H&R guy due to having run them for 10+ years without a single problem. From street to track they are the some of the best riding and handling coils on the market. Driven a lot of KW and Koni setups, personally only had one good experience with Koni and that was a full custom setup that was dyno'd to the car.


This: 
After studying this thread many times..Here is my goals

1: Stay as close to stock as possible
2: Lower the car around 1" MAX
3: Find a thinner front sway bar (or modify the stock one) 
4: Smaller rear sway (or modify the org)
5: New shocks
6: New springs
Revamp all the rubber parts relating to suspension. 

So how would you do it? What products etc?


Still looking for suggestions. I will research the H&R springs. Probably matching them to Bilstien shocks. Heavy duty or sports?


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## TheDeckMan (Sep 26, 2004)

Billtt32 said:


> This:
> After studying this thread many times..Here is my goals
> 
> 1: Stay as close to stock as possible
> ...


Best to match them with Sports due to HD's will hit the bump stops with lowering springs and is on the lower end of the available travel. Lowering 1" max is not much. If you want to run stock height, perhaps use the stock springs with HD's. I would leave the stock front bar alone and just get a larger rear. Replacing the front control arm bushings with some Defcons to prevent the front arm deflection goes a great way to getting steering feel and single turn in setups.


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## Billtt32 (Jun 18, 2013)

DeckManDubs said:


> Best to match them with Sports due to HD's will hit the bump stops with lowering springs and is on the lower end of the available travel. Lowering 1" max is not much. If you want to run stock height, perhaps use the stock springs with HD's. I would leave the stock front bar alone and just get a larger rear. Replacing the front control arm bushings with some Defcons to prevent the front arm deflection goes a great way to getting steering feel and single turn in setups.



SO many options.

1" drop max, is due to this thread saying anything lower is counter-productive. Maybe i'll go around 1.5 and get the adjustable's needed to set the alignment right?


Here is what i have planned as of now:

Bil' Sports 

Around 1-1.5" drop springs (Suggestions) 

Max adjustable front and rear

Max Defcon's (what stage should i get, don't want major over-steer, just trying to take some under-steer out, lower the heavy front end feel. Also want to lower the body roll)

So in short, great street performance, a little drop, lighter feeling front end, while trying to keep the original ride as close to the same as i can on ruff roads etc


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## Marcus_Aurelius (Mar 1, 2012)

Billtt32 said:


> It's new suspension time. She has 224k on her, shocks springs are getting tired.
> 
> Just installed 4 new AS3 tires today.
> 
> ...





Billtt32 said:


> This:
> After studying this thread many times..Here is my goals
> 
> 1: Stay as close to stock as possible
> ...





Billtt32 said:


> SO many options.
> 
> 1" drop max, is due to this thread saying anything lower is counter-productive. Maybe i'll go around 1.5 and get the adjustable's needed to set the alignment right?
> 
> ...


Hey bud! IMO, with the direction you're taking with your suspension upgrade path, I would skip right over the matching shock/spring combo to a set of Bilstein PSS (priced competitively at about $1,000 or less). The reason I'm saying this, is because you will not have worry about matching spring rate with shock valving and stroke. The standard replacement shocks may not have the proper stroke to handle the 1" lowered springs and give you very limited effective travel range. This is specifically a concern in the rear, where there isn't much travel to begin with - plus you know with the PSS that you have a good matched set with proper valving ( BTW, the H&R coilovers that Noah recommended use the same Bilstein inverted monotubes, just packaged with better fancier hardware). 

The defcons are a good choice (they're from Mike at MCPi and not from me, but I endorse them 100%). You will need rear adjustable lateral links (commonly called rear control arms although technically they aren't), and you can get the Madmax ones at MCPi for a one stop shop, but there are other vendors. I would also do a joint/bushing refresh while you're at it (front ball joints, rearward bushing in the front control arms, strut tower bushings, swaybar bushings if needed etc.). 

Now, on the swaybar topic, I'd leave the stock rear bar, or even run a stock R32 rear bar (1mm bigger but not overwhelmingly stiffer). In the front, the options would be to modify the stock bar to be softer in rate, or simply delete it. My advice is to delete it if you decide to run coilovers -- if you go for a shock/spring combo I'd keep the bar and modify it because the set up will lack the necessary roll control without the help of the bar.


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## Billtt32 (Jun 18, 2013)

Marcus_Aurelius said:


> Hey bud! IMO, with the direction you're taking with your suspension upgrade path, I would skip right over the matching shock/spring combo to a set of Bilstein PSS (priced competitively at about $1,000 or less). The reason I'm saying this, is because you will not have worry about matching spring rate with shock valving and stroke. The standard replacement shocks may not have the proper stroke to handle the 1" lowered springs and give you very limited effective travel range. This is specifically a concern in the rear, where there isn't much travel to begin with - plus you know with the PSS that you have a good matched set with proper valving ( BTW, the H&R coilovers that Noah recommended use the same Bilstein inverted monotubes, just packaged with better fancier hardware).
> 
> The defcons are a good choice (they're from Mike at MCPi and not from me, but I endorse them 100%). You will need rear adjustable lateral links (commonly called rear control arms although technically they aren't), and you can get the Madmax ones at MCPi for a one stop shop, but there are other vendors. I would also do a joint/bushing refresh while you're at it (front ball joints, rearward bushing in the front control arms, strut tower bushings, swaybar bushings if needed etc.).
> 
> Now, on the swaybar topic, I'd leave the stock rear bar, or even run a stock R32 rear bar (1mm bigger but not overwhelmingly stiffer). In the front, the options would be to modify the stock bar to be softer in rate, or simply delete it. My advice is to delete it if you decide to run coilovers -- if you go for a shock/spring combo I'd keep the bar and modify it because the set up will lack the necessary roll control without the help of the bar.



Thanks for taking the time to reply! More questions for ya! 

So how will this setup differ in ride and performance from stock. (good and bad?) 
Bil' PSS *Question:* Should i order them with any custom work done? TT 3.2 2005 s-line
Remove front sway bar
R 32 bar *Question:* Why run a r32 bar if its about the same as the stock tt bar?





Yes, when the work is done, i will replace, good or bad, all the rubber parts on the suspension & Joints, Bush's, Links....car is 224k so it all needs to go.


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## Marcus_Aurelius (Mar 1, 2012)

Billtt32 said:


> Thanks for taking the time to reply! More questions for ya!
> 
> So how will this setup differ in ride and performance from stock. (good and bad?)
> Bil' PSS  *Question:* Should i order them with any custom work done? TT 3.2 2005 s-line
> ...


Ride will be more firm than OEM (read sportier) but not harsh or bouncy. There is no need to get any custom work done to them for your use, just rock them as they come and enjoy a good set of coils. The R32 rear bar is 15mm vs 14mm in our TT - without custom springs with higher rates, the R bar can be used to give that little extra rear roll rate and improve the overall balance/feel a bit. The R32 bar is nice because it is not overly stiff like the other aftermarket offerings and not as intrusive to the dynamics. I drilled new holes in the R bar I used to make it adjustable, so that could be done as well to allow more flexibility. 

PS: the modified R32 bar I used for a while is up for sale. PM me if interested! :beer:


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## Atl-Atl (Jun 7, 2006)

Marcus

You don't know me and I don't know you. However, based on this thread and some others I have come across since buying my TT I decided to grab a set of PSS's for my car. I was going to spend the money on some fancy adjustable racekar parts but decided I didnt know what I was doing, would likely screw it up, will probably only do a few track days this summer and you seem to have a decent grasp on this suspension thing so I followed your PSS suggestion. They should show up this week and I will install them Saturday. Looking forward to giving my feedback in the near future. I will probably spend the majority of my driving time much too low for optimal handling but I promise to put the money saved towards track time with professional instruction! :thumbup:


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## aircooled56 (Jul 6, 2006)

Don't know why I haven't subscribed to this thread, keep up the great work! The concept of smaller sway bars does make sense to me, though I was told by an ex-APR driver that they have a lot of success running more front bar, but again there are other variables at work then I know of and it is a different chassis. I run hollow aftermarket bars on full soft all around to reduce unsprung weight and also to be less intrusive on the dynamics. I use RSS's with slightly higher front spring rates (+50lbs) to cope with the additional grip produced by the full slicks I run. It's been a great combo for me the past few years. I've taken care to remove as much weight from the car as possible, especially off of the nose and replacing some of the weight in the form of ballast in the rear and low on the chassis. I've always ran my best lap times with a full or nearly full tank of gas.

:thumbup:


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## Marcus_Aurelius (Mar 1, 2012)

Atl-Atl said:


> Marcus
> 
> You don't know me and I don't know you. However, based on this thread and some others I have come across since buying my TT I decided to grab a set of PSS's for my car. I was going to spend the money on some fancy adjustable racekar parts but decided I didnt know what I was doing, would likely screw it up, will probably only do a few track days this summer and you seem to have a decent grasp on this suspension thing so I followed your PSS suggestion. They should show up this week and I will install them Saturday. Looking forward to giving my feedback in the near future. I will probably spend the majority of my driving time much too low for optimal handling but I promise to put the money saved towards track time with professional instruction! :thumbup:


Hey bud, good choice and you won't regret it. I'm glad this thread and my inputs have influenced your choice. Been watching your progress thread but never posted (the technical nature of my posts isn't always well received nowadays). Feel free to ask any suspension related question and bring any feedback you may have in here, the old timers will be there to guide and discuss. :beer:




aircooled56 said:


> Don't know why I haven't subscribed to this thread, keep up the great work! The concept of smaller sway bars does make sense to me, though I was told by an ex-APR driver that they have a lot of success running more front bar, but again there are other variables at work then I know of and it is a different chassis. I run hollow aftermarket bars on full soft all around to reduce unsprung weight and also to be less intrusive on the dynamics. I use RSS's with slightly higher front spring rates (+50lbs) to cope with the additional grip produced by the full slicks I run. It's been a great combo for me the past few years. I've taken care to remove as much weight from the car as possible, especially off of the nose and replacing some of the weight in the form of ballast in the rear and low on the chassis. I've always ran my best lap times with a full or nearly full tank of gas.
> 
> :thumbup:


Welcome aboard! I've watched your aero mods and like the unique and DIY approach you've taken with your car (also stole your GT500 hood extractor vent mod for my car, the thing had an open hole in the hood begging for something functional to go there). :thumbup:


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## Atl-Atl (Jun 7, 2006)

Marcus_Aurelius said:


> Hey bud, good choice and you won't regret it. I'm glad this thread and my inputs have influenced your choice. Been watching your progress thread but never posted (the technical nature of my posts isn't always well received nowadays). Feel free to ask any suspension related question and bring any feedback you may have in here, the old timers will be there to guide and discuss. :beer:


I will be putting them on tomorrow night at my buddies shop then going to four different car related events around Denver this weekend. I like to call it "opening weekend" for car guys around here. Surely there will be some epic canyon carving with our beautiful weather forecast! 85 degrees, sunny, calm, sticky tires and new suspension!!!


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## D2O (May 12, 2012)

Atl-Atl said:


> I will be putting them on tomorrow night at my buddies shop then going to four different car related events around Denver this weekend. I like to call it "opening weekend" for car guys around here. Surely there will be some epic canyon carving with our beautiful weather forecast! 85 degrees, sunny, calm, sticky tires and new suspension!!!


I am interested in what your rear springs look like once you get them on. I picked up a set of PSS9's and the rear springs seem to be collapsed. I recall reading somewhere that this was common - did Bilstien fix this? The set I got is used so might be an older spring (E4-FD1-Y 411 A00). Is there a different spring that I should be running in the rear?


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## Late__Apex (Dec 2, 2007)

D2O said:


> I am interested in what your rear springs look like once you get them on. I picked up a set of PSS9's and the rear springs seem to be collapsed. I recall reading somewhere that this was common - did Bilstien fix this? The set I got is used so might be an older spring (E4-FD1-Y 411 A00). Is there a different spring that I should be running in the rear?


Dead coils (collapsed) are an inexpensive alternative to helper springs. This design keeps the spring seated at full droop. Don't worry about it unless you are striving for highest performance - then linear springs and helpers are the way to go.


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## Marcus_Aurelius (Mar 1, 2012)

D2O said:


> I am interested in what your rear springs look like once you get them on. I picked up a set of PSS9's and the rear springs seem to be collapsed. I recall reading somewhere that this was common - did Bilstien fix this? The set I got is used so might be an older spring (E4-FD1-Y 411 A00). Is there a different spring that I should be running in the rear?





Late__Apex said:


> Dead coils (collapsed) are an inexpensive alternative to helper springs. This design keeps the spring seated at full droop. Don't worry about it unless you are striving for highest performance - then linear springs and helpers are the way to go.


Like Steve said, having one or two dead coils is not an issue and can be used as a cheap substitute for helper springs. 

However, the rear of our cars, with very limited compression travel (about 2" from ride height and 3.9" from full droop), and low space between the trailing arm spring perch and the frame, is not the place where collapsed or helper spring would have any practical use. The rear spring used in several coilovers like the pss9 and KW v3 have had issues because of the lack of space where the spring is lodged. Any large diameter spring (like the barrel type used in the PSS9) will suffer and have collapsed coils. This is a bad condition and should be addressed if you care about your suspension. 

Using more compact linear spring with less coils is the solution IMO. I know that Bilstein is aware of the problem with our platform, and have tried to fix it with a hardware change, but they're not a spring company and probably very limited in the hardware at their disposal to properly fix the problem. Simply put, the spring they're trying to use in the rear of our cars are designed to work in applications with a lot more room for the spring to expand and compress. 

If your rear springs look like this, you need to come up with a solution


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## D2O (May 12, 2012)

Marcus_Aurelius said:


> Like Steve said, having one or two dead coils is not an issue and can be used as a cheap substitute for helper springs.
> 
> However, the rear of our cars, with very limited compression travel (about 2" from ride height and 3.9" from full droop), and low space between the trailing arm spring perch and the frame, is not the place where collapsed or helper spring would have any practical use. The rear spring used in several coilovers like the pss9 and KW v3 have had issues because of the lack of space where the spring is lodged. Any large diameter spring (like the barrel type used in the PSS9) will suffer and have collapsed coils. This is a bad condition and should be addressed if you care about your suspension.
> 
> ...


Yup - that is exactly what they look like. I had the car out at an autocross event today and the rear felt 'unpredictable'. I suspect it is a poor combination of these springs and the over-rated sway bar.
Any suggestion who to look into? H&R? Will I have any issue with the valving in the shock switching to a linear spring?


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## Marcus_Aurelius (Mar 1, 2012)

D2O said:


> Yup - that is exactly what they look like. I had the car out at an autocross event today and the rear felt 'unpredictable'. I suspect it is a poor combination of these springs and the over-rated sway bar.
> Any suggestion who to look into? H&R? Will I have any issue with the valving in the shock switching to a linear spring?


There are no issues with switching to a conventional linear spring. The only thing you need to keep in mind is the spring rate. Don't stray too far from the rate of the ones you're replacing, that way you're still within the valving window of the shocks. 

What rear swaybar are you using? I have a modified set of OEM 15mm R32 (about 10-20% stiffer depending on adjustment hole used) that I was about to put in the classified. It's IMO the best balance for the car on coilovers with the spring rate range that you're using. Being that you're autocrossing, you get first dibs before I put it out there for the sharks. :beer:


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## D2O (May 12, 2012)

Honestly I'll have to check - I think it is H&R 19mm. For this set up it is definitely too much (I was told I am getting rear wheel lift).
I'll shoot you an email about the R32 bar.


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## Late__Apex (Dec 2, 2007)

Marcus_Aurelius said:


> There are no issues with switching to a conventional linear spring. The only thing you need to keep in mind is the spring rate.


...and length & the adjustability of your perch. You may need a helper/tender spring to get the correct ride height without having it unseat at droop. When I went linear that's what I needed but I was running the FWD platform


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## Marcus_Aurelius (Mar 1, 2012)

^^^ Steve, that is definitely a FWD thing. In the multi-link rear, the spring location has no room and use a really short spring (4" IIRC). With adjusting perches (or even without) there is no room/need for helpers or tenders - remember we're only dealing with 3.5" of dynamic shock stroke with the factory bumpstops intact (3.9" from full compression to full droop with the bumpstops chopped).


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## Tempes_TT (Oct 24, 2010)

Marcus_Aurelius said:


> If your rear springs look like this, you need to come up with a solution


Really good stuff. 

Im experiencing "should have done it right the first time" syndrome with my suspension components. With the front assembly blown, and collapsed rear springs, Im out looking for a worthwhile investment. :thumbup:


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## Marcus_Aurelius (Mar 1, 2012)

Tempes_TT said:


> Really good stuff.
> 
> Im experiencing "should have done it right the first time" syndrome with my suspension components. With the front assembly blown, and collapsed rear springs, Im out looking for a worthwhile investment. :thumbup:


What's the ultimate goal and use for the suspension upgrade?


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## Tempes_TT (Oct 24, 2010)

Marcus_Aurelius said:


> What's the ultimate goal and use for the suspension upgrade?


Road course. I have no intentions, right now at least, to make this a purpose built track machine, but I do plan to spend a fair amount driving on them.


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## Marcus_Aurelius (Mar 1, 2012)

I think you may be a good candidate for a set of H&R RSS. They will be superb on the road course and can still be daily driven (especially if the roads in your area aren't like what we have here in Metro NY). Heck, you might even be able to turn them into the perfect dual purpose coilovers by using the slightly softer H&R street springs. The RSS valving will accept the the street spring rates, and still provide amazing road holding capability. The RSS are also well priced for what they are, you can find them at around $1300 with a bit of shopping around. :beer:


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## MCPaudiTT (Nov 26, 2006)

Do you have a source for finding specific spring rates? All the sites I find want to know the application and then push you in to "known" systems... I want to specify length and spring rate and have them show me options. What do you do to find different spring rate options?


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## All_Euro (Jul 20, 2008)

Good question regarding the spring rates... I need to order replacements for failed rear springs (Vogtland coilovers) but it seems like you have to write or call to get that info. Here are a couple sites I found...

http://www.swiftsprings.net/products/sport-compact.html
http://www.ground-control-store.com/products/category.php/CA=211


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## aircooled56 (Jul 6, 2006)

Marcus_Aurelius said:


> I think you may be a good candidate for a set of H&R RSS. They will be superb on the road course and can still be daily driven (especially if the roads in your area aren't like what we have here in Metro NY). Heck, you might even be able to turn them into the perfect dual purpose coilovers by using the slightly softer H&R street springs. The RSS valving will accept the the street spring rates, and still provide amazing road holding capability. The RSS are also well priced for what they are, you can find them at around $1300 with a bit of shopping around. :beer:



I only have the best of things to say about the RSS's. They have served me well over the past few years on our shared platform :thumbup:


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## Marcus_Aurelius (Mar 1, 2012)

MCPaudiTT said:


> Do you have a source for finding specific spring rates? All the sites I find want to know the application and then push you in to "known" systems... I want to specify length and spring rate and have them show me options. What do you do to find different spring rate options?


Mike, Eibach ERS line is the best source, that's what I use and recommend (although there are others like H&R, Afco etc.). Ground Control is a good distributor of the ERS spring line, and have an easier site to order them compared to the massive Eibach site where you could easily get lost looking for something specific. 


http://www.ground-control-store.com/products/description.php/II=944/CA=211


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## MCPaudiTT (Nov 26, 2006)

Marcus_Aurelius said:


> Mike, Eibach ERS line is the best source, that's what I use and recommend (although there are others like H&R, Afco etc.). Ground Control is a good distributor of the ERS spring line, and have an easier site to order them compared to the massive Eibach site where you could easily get lost looking for something specific.
> 
> 
> http://www.ground-control-store.com/products/description.php/II=944/CA=211


Even their link is 404 for the catalog!!! http://performance-suspension.eibac...nsion.eibach.com/files/catalogs/ERS_18_US.pdf


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## MCPaudiTT (Nov 26, 2006)

MCPaudiTT said:


> Even their link is 404 for the catalog!!! http://performance-suspension.eibac...nsion.eibach.com/files/catalogs/ERS_18_US.pdf


OK. looks like the new REV is 19, so that's why 18 is 404...

http://eibach.com/sites/devperformance-suspension.eibach.com/files/catalogs/ERS_19_US.pdf

Thanks Max!


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## MCPaudiTT (Nov 26, 2006)

Still struggling to find the ones you discussed... Can you tell me part number for these that you posted OTOF?

"700/1300 lbs spring upgrade (replacing 560/1150 lbs)"

At least that should get me to the right section of the catalog!


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## Marcus_Aurelius (Mar 1, 2012)

Mike, I would need to know what diameter or ID spring your coilover uses. Eibach ERS part numbers are easy to decode though - there are 3 sets of numbers, the first one is the length, second one is the ID, and the last one is the rate. For example, a 2.5" ID spring in 6" length for the front with a 700 lbs/in rate would have the following part# 0600 250 0700


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## Marcus_Aurelius (Mar 1, 2012)

^^^ And you might have to get a custom ERS spring for the rear because their short 4" off-the-shelves springs line don't go up to the rate you're after. Call ground control and tell them what you want/need and they'll get you squared away (unlike the other places, they're a real race-oriented business that will know about special spec springs)


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## All_Euro (Jul 20, 2008)

Jacked the front of my car up and the front drivers damper is moving around like spaghetti... and that just doesn't seem right. So I've been looking around at replacement options and I think a set of PSS's would fit the bill nicely - the more exotic options aren't in the budget atm unfortunately. Plus the lifetime warranty on the Bilstein's is looking pretty good right now.

What kind of experiences have people had with stiffer spring rates/valving in cold weather? By cold I mean in the -25*C and colder neighbourhood... so -10*F to -40*F. I've read of people buying the PSS9's to soften up the settings a little in the winter but not sure that's needed with 460/680 rates... thoughts?

On a side note, the back springs had previously failed on these coils and I replaced them with some Eibach ERS's - nice springs and the guys at Ground Control were great to deal with :thumbup:

In my suspension search I also came across this site that has some pretty good articles in the left hand column... http://farnorthracing.com/books.html


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## Neb (Jan 25, 2005)

I drove my TT on H&R's all winter through that cold weather with no issues at all. Didn't even make the slightest difference.


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## All_Euro (Jul 20, 2008)

Thanks Neb, that's really helpful as StatsCan says Ottawa and Calgary have similar average temps in January. The price difference between the PSS's & PSS9's is $1000 so I think I'll save that and put it to use elsewhere :beer:


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## hemicuda1313 (Jun 22, 2007)

I love this thread! I am working on refreshing my suspension on my 02 225Q (everything is original). Planning on the PSS coils, DEFCON stuff, and more but I am curious what bushings people would go OEM or Poly? I am focused on developing the car into a capable and fun daily with mostly hard driving through the mountains. Thoughts?


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## Marcus_Aurelius (Mar 1, 2012)

hemicuda1313 said:


> I love this thread! I am working on refreshing my suspension on my 02 225Q (everything is original). Planning on the PSS coils, DEFCON stuff, and more but I am curious what bushings people would go OEM or Poly? I am focused on developing the car into a capable and fun daily with mostly hard driving through the mountains. Thoughts?


Good plans, the PSS are great daily colilover. With the Defcons spacers, both rubber or poly will work fine and be a great improvement. Poly bushings does provide extra firmness but that might not be worth it for the use you have for the car, my car if it was only a DD, would probably be on Defcons with rubber bushings.


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## hemicuda1313 (Jun 22, 2007)

Marcus_Aurelius said:


> Good plans, the PSS are great daily colilover. With the Defcons spacers, both rubber or poly will work fine and be a great improvement. Poly bushings does provide extra firmness but that might not be worth it for the use you have for the car, my car if it was only a DD, would probably be on Defcons with rubber bushings.


Thanks for the feedback. What would you recommend for all other suspension bushings? Which would you do poly and which OEM? I want to refresh it all over the winter.


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## Tiero (Feb 13, 2007)

hemicuda1313 said:


> Thanks for the feedback. What would you recommend for all other suspension bushings? Which would you do poly and which OEM? I want to refresh it all over the winter.


The only ones worth making poly are the front control arm bushings. You don't want the rears to be poly because they should be free to let the arms move up and down effortlessly. Poly bushings will reduce side to side and up and down movement because they aren't flexible. Also, you risk them ovaling over time and performing much worse.

The rest are really a judgement call. I did top mounts and sway bar bushings in poly but I may go back to oem for the top mounts. I'm getting a strange clunk that I can't seem locate despite having no play and all new parts.


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## hemicuda1313 (Jun 22, 2007)

Ok. Looking at online retailers and have some questions. Here is the plan and a few more detailed questions for the experts:

*Bilstein PSS Coilovers* - Where to purchase? I seem to find them to be much more than $1000 mentioned a few times in the thread. Is there a place that does quarterly sales?
*R32 Rear Swaybar* - possibly modified
*DEFCON 1 or Track* - Recommendations requested?
*MCPi MadMax Control Arms*
*Front Bushings -* OEM or Poly?
Front Wishbone Front
Front Wishbone Rear
Front AntiRoll Bar
Dogbone Mount
Steering Rack Mount
*Rear Bushings* - OEM or Poly? 
Rear Wishbone Front
Rear Control Arm
Rear AntiRoll Bar


What else am I missing? Should I look at any camber correction?


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## MCPaudiTT (Nov 26, 2006)

hemicuda1313 said:


> What else am I missing? Should I look at any camber correction?


Tie rod ends
Swaybar droplinks
Subframe bushes (depending on what you want the car "to be")


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## max13b2 (Jul 24, 2007)

As far as the PSSs, wait for AWE to run a sale. They are a forum sponsor and frequently run sales. I did just that and got set for around $1050 shipped. I'll elaborate more on my Max inspired setup later, but I have asked all the same Qs as you to him and have gotten great, informative answers.

Edit: just checked and they are running them on sale NOW for $1050


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## 20v master (May 7, 2009)

Tiero said:


> I'm getting a strange clunk that I can't seem locate despite having no play and all new parts.


What top mounts in poly did you go with? I'm having the same issue.


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## Tiero (Feb 13, 2007)

20v master said:


> What top mounts in poly did you go with? I'm having the same issue.


Powerflex but, I had the clunk before i replaced the top mounts.


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## Marcus_Aurelius (Mar 1, 2012)

Marcus_Aurelius said:


> I took some measurements for you to figure out the rear damper vs wheel ratio. Each inch of wheel travel is equivalent to 0.8" of damper travel in both directions.
> 
> *-Compression* (starting at static ride height)
> 
> ...





^^^ Related to this post, I made this video because I'm taking my shocks out to be refreshed and revalved, therefore I needed to have some visual insight of the dynamic rear wheel behavior to guide my valving decisions (the front is pretty much figured out). 


It might not be much to the general population because my spring rates are so high, but it gives an idea how much movement is still present even in moderate street driving with 1,300 lbs springs. If you're running low in the rear and/or have some soft springs, just know that you're likely riding the bumpstops in many dynamic situations (laterally loaded suspension and hitting a bump on the surface for example). 


https://m.youtube.com/watch?feature=youtu.be&v=aPqXC4NmNNs


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## TheDeckMan (Sep 26, 2004)

Your right Max, that is a lot of travel under normal driving conditions  looks close to 12mm to 15mm or so.


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## 225TTed (Nov 28, 2014)

Makes me not feel warm and fuzzy about running stock height with the R32 suspension... even when I drop HD's in there, it's still going to completely collaspe.


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## andrew1984 (Jun 24, 2002)

how much were you able to trim rear bump stop?


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## Marcus_Aurelius (Mar 1, 2012)

I just chopped them in half (maybe a bit more past halfway) -- You'll be able to get about an inch of additional travel. Sorry I didn't put more thought into it and took measurements, it's one of these thing where every little bit helps and you have to leave some cushion against bottoming out... so about halfway instinctively feels right. :beer:


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## 225TTed (Nov 28, 2014)

Marcus_Aurelius said:


> I just chopped them in half (maybe a bit more past halfway) -- You'll be able to get about an inch of additional travel. Sorry I didn't put more thought into it and took measurements, it's one of these thing where every little bit helps and you have to leave some cushion against bottoming out... so about halfway instinctively feels right. :beer:


Would you recommend trimming the bumpstops with a Bilstien/R32 spring setup? I know we need basically all the travel we can get, and it's limited by the rear suspension.


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## Marcus_Aurelius (Mar 1, 2012)

Yes, trim the bumpstops. The rear ones are OEM and conservative. Any setup will welcome and benefit from some extra travel before sitting on the stops (the front is dependent on what comes with the front strut used).


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## 225TTed (Nov 28, 2014)

Marcus_Aurelius said:


> Yes, trim the bumpstops. The rear ones are OEM and conservative. Any setup will welcome and benefit from some extra travel before sitting on the stops (the front is dependent on what comes with the front strut used).


My dude! Much appreciated! I'm confident with the HD's, new bushings everywhere, and a cat welded in where the oem one was, this may be a decent setup for the daily commute and track time.


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## nitroTT (Jun 20, 2015)

Hi ive been reading and found most people use koni, bilstein, h&r 
My question is which is the best for performance, lightest, and under 1500 usd. For mk1 tt quattro
I dont care about the ride quality but my roads do have the pothole disease 
Im thinking my options are 
Koni 1150 series adjustable
Bilstein pss fixed
H&r street performanc ss
Or am i missing one? 
Thanks


Sent from my LGLS770 using Tapatalk


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## ramone23456 (Dec 29, 2009)

nitroTT said:


> Hi ive been reading and found most people use koni, bilstein, h&r
> My question is which is the best for performance, lightest, and under 1500 usd. For mk1 tt quattro
> I dont care about the ride quality but my roads do have the pothole disease
> Im thinking my options are
> ...


I run Koni FSDs with Eibach springs. They're comfortable, but handle very well. If you're not tracking the car I would look at these closely, especially with the rough roads.


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## nitroTT (Jun 20, 2015)

I do plan on taking the car to the track and would rather have it set up more for that

Sent from my LGLS770 using Tapatalk


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## bwdz (Jan 21, 2015)

This winter I did the Bilstein coilovers and could not be happier. They are not adjustable. They are aluminum and way lighter than the stock struts. The ride is only a tad stiffer and the rebound is fantastic, I live near Detroit where I am regularly airborne on terrible roads. I did all poly bushings in every control arm and trailing arm, I used the offset bushings from ECS in the rear so I can set rear camber and it gave me plenty of adjustment as I am not "slammed". Played with some alignment settings and car is track ready balanced with the rear coming out just before the front end lets loose, essentially tail hangs out about 10-15 degrees in a full power slide on a turn. I paid $1067 from ECS but I think it was just a set they had on the shelf, they matched the price for me that CARID was willing to give me plus I spent a couple grand all together on other things with them.


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## Wolfeie (Oct 22, 2015)

bwdz said:


> This winter I did the Bilstein coilovers and could not be happier. They are not adjustable. They are aluminum and way lighter than the stock struts. The ride is only a tad stiffer and the rebound is fantastic, I live near Detroit where I am regularly airborne on terrible roads. I did all poly bushings in every control arm and trailing arm, I used the offset bushings from ECS in the rear so I can set rear camber and it gave me plenty of adjustment as I am not "slammed". Played with some alignment settings and car is track ready balanced with the rear coming out just before the front end lets loose, essentially tail hangs out about 10-15 degrees in a full power slide on a turn. I paid $1067 from ECS but I think it was just a set they had on the shelf, they matched the price for me that CARID was willing to give me plus I spent a couple grand all together on other things with them.


Willing to post up your shopping list? Would love to have that as a reference for when it's my turn.


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## bwdz (Jan 21, 2015)

Well, I did the steering rack and tie rods last year so those stayed put. I did the balljoints (Lamforder, don't go cheapies on those or they won't last) Powerflex bushings in the front control arms, the ECS dog bone mount with poly (hint, don't use their bolts, they seemed cheap and my factory ones looked great so I reused them) Powerflex trailing arm bushings, Powerflex rear control arm bushings and the offset ones on one set to be able to adjust camber (I am only 1.5 inches lower in the back so it had plenty of adjustment without going to adj control arms). I used rubber in the sway bars as they sent me wrong size poly so I just didn't feel like going back in there, my front sway bar was way bigger than the bushings they set it measures around 21mm. I also used the ECS coilover install kit with hardware, wish I went with different strut mount bushings as I hear they won't last but so far so good. Front is dropped 1.25".


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## vtraudt (Mar 1, 2010)

*Audi TT rear sway bar modification*

Here is link to making the rear stiffer (for less understeer) 

http://www.ttforum.co.uk/forum/viewtopic.php?f=2&t=1132337&hilit=Drilling+rear+swaybar


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## Carzculture#9 (Dec 3, 2019)

Amazing information.


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