# Corrado single piston and Audi dual piston brake weights



## Skaven (Nov 17, 1999)

I decided to see if the Audi dual-piston calipers indeed bolt on to the Corrado G60 brakes - sure enough they did! They even clear the 15" Corrado steel wheels. I also decided to see how much both sets of brakes weigh..
Corrado Single Piston caliper, pads, carrier: 10lbs
Audi Dual Piston caliper, pads, carrier: 16lbs
















Sorry about the B&W pics - forgot to change my digicam mode. I also wasn't able to take pics of the single piston stuff - but I assure you it was 10lbs.
I think I'm going to swap the dual piston brakes onto the car. I would like to do some performance tests to see what the braking distance is - but I have no idea what kind of pads the single piston brakes have. I plan on putting Hawk street pads on the dual piston setup. So it won't really be a fair comparison. I'll keep you guys posted though.


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## PowerDubs (Jul 22, 2001)

*Re: Corrado single piston and Audi dual piston brake weights (Skaven)*

Wow.
That is a BIG difference. Not worth it if you ask me, unless you are going to be strictly track racing.


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## 155VERT83 (Aug 1, 2000)

*Re: Corrado single piston and Audi dual piston brake weights (PowerDubs)*


_Quote, originally posted by *PowerDubs* »_Wow.
That is a BIG difference. Not worth it if you ask me, unless you are going to be strictly track racing.

Ditto. 60% weight gain? http://****************.com/smile/emthdown.gif Do the dual piston calipers provide 60% more braking?


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## Skaven (Nov 17, 1999)

*Re: Corrado single piston and Audi dual piston brake weights (155VERT83)*


_Quote, originally posted by *155VERT83* »_
Ditto. 60% weight gain? http://****************.com/smile/emthdown.gif Do the dual piston calipers provide 60% more braking? 

Did the car gain 60% of its weight?!?








People add wheels and tires that add WAY more than 6lbs at all four corners! And thats rotational weight! I would be willing to put money down that you guys would notice no difference driving a car with the "heavier" calipers - outside of braking performance.


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## Evilclown (Mar 12, 2001)

*Re: Corrado single piston and Audi dual piston brake weights (Skaven)*

I'd notice an extra 12lbs of total unsprung weight. So would you; that's a huge difference. It would really change the ride and handling of the car, and not for the better.


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## Skaven (Nov 17, 1999)

*Re: Corrado single piston and Audi dual piston brake weights (Evilclown)*

According to this suspension design link

_Quote »_Unsprung weight represents a significant portion of the total weight of the vehicle. In today's standard-size automobile, the weight of unsprung components is normally in the range of 13 to 15 percent of the vehicle curb weight. 

I've seen the weight of my '92 GTI at ~2400 lbs. So lets take best case: 13% of 2400 = 312lbs of unsprung weight. 12 additional pounds of unsprung weight would be ~ 3.8% difference. I'm not saying it isn't adding weight - just pointing out if it would be noticeable. People put wheels/tires on their car that are 10-15lbs heavier EACH - most of them seem to think their cars handle better!
I guess the true test is if braking distance decreases. I'll keep you guys posted on that.


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## VWGolfA4 (Apr 5, 2000)

*Re: Corrado single piston and Audi dual piston brake weights (Skaven)*

I would go with the Duals, I am sure they stop better, and yes you might notice the heavier front, but only in an extreme case. The better brakes are worth the extra 12lbs...


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## bxr140 (Jul 18, 2002)

*Re: Corrado single piston and Audi dual piston brake weights (VWGolfA4)*


_Quote, originally posted by *VWGolfA4* »_I would go with the Duals, I am sure they stop better, and yes you might notice the heavier front, but only in an extreme case. The better brakes are worth the extra 12lbs...

absolutely incorrect speculation. the dual piston calipiers will do nothing for braking, in a truly "all else equal" situation. you will notice a different "feel" to the pedal, as the amount of fluid being pushed will be different, but you will NOT be able to generate any more usable clamping force at the caliper with the g60 calipers.
if a difference is found in a test, it is due to inaccuracies in the testing, or a hidden not-quite-so-equal variable. 
actually, i take that back...if you do the testing over a rough surface, the lighter caliper will provide BETTER braking in an "all else equal" situation, as there will be better and more consistent traction with less unsprung weight. 
will the weight be noticible in normal driving? no...unless you drive over really bumpy roads. will the average guy notice the weight difference in a "performance" situation? probably not. then again, if you can't notice 6 pounds on each corner, you probably don't have the skills to warrant "upgrades" anyway. 
course, in the true sense of the word, the dual piston g60 is NOT an upgrade. bottom line, when you compare the g60 caliper and the...g60...caliper, you can only hope for "almost as good" performance from the heavier dual piston.


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## Evilclown (Mar 12, 2001)

*Re: Corrado single piston and Audi dual piston brake weights (bxr140)*

Yeah, what he said.
If you're looking to upgrade your 11" brakes, switch to better rotors, pads and fluid. If you want more than that, get a Wilwood kit.


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## Todd_hyperformance (Dec 10, 2002)

*Re: Corrado single piston and Audi dual piston brake weights (bxr140)*


_Quote, originally posted by *bxr140* »_
absolutely incorrect speculation. the dual piston calipiers will do nothing for braking, in a truly "all else equal" situation. you will notice a different "feel" to the pedal, as the amount of fluid being pushed will be different, but you will NOT be able to generate any more usable clamping force at the caliper with the g60 calipers.
if a difference is found in a test, it is due to inaccuracies in the testing, or a hidden not-quite-so-equal variable. 
actually, i take that back...if you do the testing over a rough surface, the lighter caliper will provide BETTER braking in an "all else equal" situation, as there will be better and more consistent traction with less unsprung weight. 
will the weight be noticible in normal driving? no...unless you drive over really bumpy roads. will the average guy notice the weight difference in a "performance" situation? probably not. then again, if you can't notice 6 pounds on each corner, you probably don't have the skills to warrant "upgrades" anyway. 
course, in the true sense of the word, the dual piston g60 is NOT an upgrade. bottom line, when you compare the g60 caliper and the...g60...caliper, you can only hope for "almost as good" performance from the heavier dual piston. 

I'm not really sure where you’re getting this from. Just a caliper swap will make a minimal difference in overall breaking force, this is true. The dual piston calipers are a more rigid design than the vw single piston units, and have a much larger pad. This IS going to provide improved clamping force, because less hydraulic pressure is being wasted flexing the caliper. The larger pads will lend to increased pad life, and much greater pad thermal capacity. The thermal capacity of the pad is important, because this has a lot to do with how long the pads will last before they get 'cooked'. 
We've been putting these calipers on cars as far back as '94. I used to have a scirocco with our 11" dual piston conversion, and let me tell you that the performance was definitely there. The extra weight is not noticeable, and to use that 'everything being equal' argument is truly just splitting hairs. I'm speaking from direct experience here, not speculation. 
While I don't generally tell people to put dual piston units on a car that already has the single piston 11" setup, if you are going up to 11", then genuinely consider using the bigger calipers.


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## bxr140 (Jul 18, 2002)

*Re: Corrado single piston and Audi dual piston brake weights (Todd_hyperformance)*


_Quote, originally posted by *Todd_hyperformance* »_ The dual piston calipers are a more rigid design than the vw single piston units, and have a much larger pad. This IS going to provide improved clamping force, because less hydraulic pressure is being wasted flexing the caliper.

incorrect. its true that a more rigid caliper WILL use the hydraulic pressure more efficiently, be you will NOT be able to generate ANY more clamping force with ANY caliper, in an "all else equal" situation. clamping force is NOT the weak link in the system, and as such, the greater clamping force POTENTIAL that comes along with multi-piston calipers is irrelevant. 
also, i THINK the girling dual calipers have same-sized pistons, although i'm not positive. if so, thats another strike in their favor. 

_Quote, originally posted by *Todd_hyperformance* »_ The larger pads will lend to increased pad life, and much greater pad thermal capacity. The thermal capacity of the pad is important, because this has a lot to do with how long the pads will last before they get 'cooked'. 

not quite. larger pads do NOT last longer simply becase they are larger. the rate at which a pad wears is mesured in the direction normal to the friction surface--in other words it has NOTHING to do with the other dimensions. the only reason pads of the same material and different sizes might wear at different rates is due to the fact that the pads would not be used at the same temperature. 
you are somewhat on the right track bringing up the thermal issue...heat IS the limiting factor in maximum braking performance. HOWEVER, the actual 'thermal capacity' of a pad (which is a very vauge term) is much less of a concern than the 'thermal capacity' of the entire system. 
to be more specific, the biggest heat related factor for the pads is their operating range. as such, pad MATERIAL is a MUCH more relavant issue than pad SIZE, especially when you consider the practical applications available. many of the street performance pads (DS2500, R4S) will have a maximum operating temp that is close to, if not more than TWICE that (in degrees F, at least) of an OEM replacement, such as redbox. 

_Quote, originally posted by *Todd_hyperformance* »_I used to have a scirocco with our 11" dual piston conversion, and let me tell you that the performance was definitely there.


this is the kind of misinformation and half-truth that plagues the VW tuning industry. the implied meaning of this statement far exceeds its fact-based truth. 
in other words, the "performance was there" relative to what? what kind of components were in the system? what kind of car was it attached to? in what kind of situations did you use the setup? what was the baseline and what other "upgrades" were attempted?

_Quote, originally posted by *Todd_hyperformance* »_The extra weight is not noticeable, and to use that 'everything being equal' argument is truly just splitting hairs. 


no, the "everthing else equal" argument is what separates those who THINK they have made a performance upgrade from those who just bolted on a bigger, prettier, or more expensive component.
reagarding the weight, like i said, some people will notice the weight, others will not. if youre flogging down your average "fun road", its pretty easy to notice a 4-5 pound difference at each corner. if you can't...well...


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## Skaven (Nov 17, 1999)

*Re: Corrado single piston and Audi dual piston brake weights (bxr140)*


_Quote, originally posted by *bxr140* »_
also, i THINK the girling dual calipers have same-sized pistons, although i'm not positive. if so, thats another strike in their favor. 


If fact, they are NOT the same-sized pistons. One is smaller than the other. I'm curious as to why same-size pistons would be a strike?


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## Skaven (Nov 17, 1999)

*Re: Corrado single piston and Audi dual piston brake weights (Skaven)*

Just read a great article from Grassroots Motorsports about braking systems.

_Quote, originally posted by *Grassroots Motorsports* »_In order to calculate the amount of clamping force generated in the caliper, the incoming pressure is multiplied by the area of the caliper piston. In our example, the 558 psi that had been generated at the master cylinder has traveled through the brake pipes and lines and is pushing against two 1.5-inch pistons per caliper. Therefore, the effective area of the caliper will be equal to two times the area of a single 1.5-inch piston. Working the numbers reveals that 558 psi will generate 2068 pounds of clamp load 
[558 psi x (1.84 in. x 1.84 in.) x 2]. 

Perhaps I'm not understanding the article - but it seems as though you would get more clamping force from a dual piston caliper, assuming the area of the dual pistons is greater than that of the single.








(edit) Ok, lets see if I understand - clamping force is not the weak link. You can get plenty of clamping force from the single piston caliper. By changing to the dual piston caliper - you are changing the manner in which that force gets to the rotor. So the given input force would change to get the same clamping force. The maximum clamping force would also be higher, but way beyond the point of locking up the brakes, so irrelevant?
What about brake fade? You aren't changing the rotor, so you aren't getting more thermal capacity from the rotor. But don't the pads also absorb the heat as well? Wouldn't increasing the pad size increase the total thermal capacity just as increasing the rotor size did? (and no, I don't mean in the same amount)


_Modified by Skaven at 12:31 PM 6-11-2003_


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## Todd_hyperformance (Dec 10, 2002)

*Re: Corrado single piston and Audi dual piston brake weights (bxr140)*

I'm not sure what your background is, other than a couple of articles from the Internet. A two piston caliper is going to generate more clamping force because it is more efficient. It spreads more pressure over a larger area, allowing less pad deflection, better using all of the available pad.
Let describe it like this. Compare a bench vise to a c-clamp. If you use a 6" wide bench vise to compress something, using the same amount of force to turn the same dia and pitch of screw "all things being equal" you'll get a lot more clamping force from the bench vise. The vise is more efficient, it flexes less in the body and doesn’t deflect.
A larger pad is going to last longer, even if the annulus is the same, because of the way it deals with heat. I wasn't referring to different types of pads, just comparing same compound of different sizes.
Girling calipers have differential bores, so pad taper isn't an issue.
As far as performance, back then we didn't have measuring equipment, so I can spout any numbers, but the system performed extremely well at track days, and in real world situations, it did out perform the OE system. 
As far as the potential clamping force of multi piston calipers being irreverent,







. That’s the whole point of a using them. That’s the reason audi put them on the 200 in the first place. Force and rigidity are the major factors that separate calipers in there performance. Why does Porsche now use a longer, similar annulus, 6 piston caliper on their top cars? Why not just one piston on each pad instead of three? Porsche is setting the standard for production vehicles and braking systems, and not just because they're systems are pretty. I'm just sighting another example here, not comparing the calipers we're talking about to porsche product.
I agree with you that the vw industry, as with all aftermarket arenas, is plagued with gimmicks and misinformation. I assure you that I'm not here to perpetuate that. I'm speaking from the experience that I, and all of our customers over the years, have had with these calipers. 
We can argue until we're blue in the face as to whether you can feel the extra weight. I can only tell you that NONE of our customers have ever complained, and many, many of them have been more than you average enthusiast.
Ask anyone who knows me or my company, and they will tell I THINK more than most people in this industry, almost to a fault. You keep talking like what your saying is gospel, but don't present facts to back it up. I'm presenting fact and opinion based on real world situations, not JUST theoretical.


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## Electron Man (Sep 21, 1999)

*Re: Corrado single piston and Audi dual piston brake weights (Todd_hyperformance)*

Thanks for that info Skaven.
Todd, any problems running those Girling 60s where Girling 54s (what IIRC came stock on the Corrado and Passat VR6s through 95) used to reside? I'd be more worried about increased piston volume of the Girling 60 leading to more pedal travel for the same braking force. Unless volume of both pistons is roughly equivalent to single piston volume, you'd live with increased pedal travel or replace the MC with something a little larger, right(?).
All else being equal, I think I'll just get better pads (don't track my B4).
edit: Only thing I dislike about those Girlings is the pin & dust boot set-up used so caliper floats. *CLUNK!*








Good discussion.







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


_Modified by Electron Man at 12:23 PM 6-11-2003_


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## bxr140 (Jul 18, 2002)

*Re: Corrado single piston and Audi dual piston brake weights (Skaven)*


_Quote, originally posted by *Skaven* »_Perhaps I'm not understanding the article - but it seems as though you would get more clamping force from a dual piston caliper, assuming the area of the dual pistons is greater than that of the single.









that IS a very good article. 
however, the thing you have to understand when theyre throwing out the numbers is that theyre keeping certain things constant. specifically, pedal pressure. also, theyre assuming you are NOT at the limits of the brakes...which is the area in which you are really concerned, as it is when you have your maximum forces. 
okay, so flip that section of the around. seriously...do it right now, before you keep reading. 
done? okay...so when you flip that around, it is intuitive that to get the SAME clamping force for their calipers, you would need LESS pedal PRESSURE (and consequently less hydraulic pressure) with the dual piston setup. this is a HUGE point. make sense? it should because thats absolutely true...if you got a different impression from my posts, i apologize. 
this will have the effect of "shortening" the pedal, becuase you will simply need to push the pedal less to generate the same clamping force. HOWEVER, at the same time the fact that you physically need to move more fluid to push more caliper piston surface area will have the effect of a "longer" pedal. where your car will fall (if those effects cancel out or not) also depends on some OTHER variables, most notably the condition of your fluid, and to a lesser extent your flexible lines. 
see what i mean by needing a truly "all else equal" situation? 
okay, all that was for a situation where we ASSUMED the system was operating below its limits. lets look at the limiting factor though. from our handy pulp friction article, we are well aware that the TIRES are the limiting factor in EVERY brake system, assuming fade (in other words, heat) is not an issue. 
so then lets go backwards in a situation where the tire loses traction--it locks up. you have a rolling tire/wheel/rotor assy and the road, which more or less propelled by the momentum of the car. you apply a torque to this assy against the 'forward' rotatation of the wheel assy (you apply the brakes), and it begins to decelerate due to the changing friction force between the tire and the road. at some point, for every braking situation, you will get to a point where the torque applied to the rotating assy overcomes all the momentum forces and other good stuff, and the rotating assembly stops rotating--it locks up. 
this torque, for EVERY braking situation, will have a numeric value that is independant of rotor size, caliper size, pad material, etc. it is simply a number where (in a nutshell) one foce beats out another. this is a big point here. that torque value is INDEPENDANT of what kinds of components are producing it. 
okay, so how do we GET that torque? well, its a PRODUCT of rotor size, caliper size, hyradulic pressure, and pad material. the hydaulic pressure in the system pushes the caliper pistons, which produce a clamping force on the pads. the pads produce a friction force aginst the rotor, and coupled with the distance that force is applied to the rotor (in other words, its relative to the size of the rotor) you get a torque. voila. flex or other veriables in the system are irrelavant to the final torque value...they all get soaked up by things like pedal travel. 
so if you take your baseline corrado g60 brake setup and go to lock up, you are producing this magical torque value. you can determine all of the forces and pressures if you want. if you change to the girling dual piston calipers (or any other calipers for that matter) once you produce that VERY SAME torque value, your wheel will lock up. that is simply a fact, in an all else equal situtation, of course. you can again calculate all the forces and the pressures, and there will ABSOLUTELY be some differences. however, if you use a pad of the same material (friction coefficient) and the same rotor, you will find that the friction force will be exactly the same, and as such, the clamping force which drives the friction force WILL BE EXACTLY THE SAME. however, since the clamping force is a product of the piston area and the hydraulic pressure, and we know the piston area is changed, we will find that the hydraulic pressure has also changed. that is indeed fact, and nobody will argue the contrary. 
where people get confuesd is the fact that you can indeed generate more THEORETICAL clamping force with the multi-piston caliper, and one needs only to look at your quoted paragraph from the pulp friction article for the proof. if you as a driver can only produce X amount of force on the brake pedal, large caliper pistons will absolutely produce more clamping force at your maximum X force on the brake pedal. on paper, at least. as i have shown above however, you need to understand the context of that paragraph to fully understand it. 
what it boils down to is that the calipers are NOT the weak link in the system. people who apply these kinds of "updrages" unfortunately do not fully understand the mechanics of the system, and come up with MANY incorrect conculsions. for instance, to decel a the same rate for our above two brake setups, you will indeed have LESS brake pedal pressure with the dual piston. flip that around, and for the same pedal pressure, you will be decelerating at a faster rate. facts like these can me mis-construed into "proof" that the dual piston setup is "better". hopefully you can see now that it is NOT better. just different. if you like different, kick ass. go for it. different can absolutely be better, but only on a subjective level. if youre looking for something that is OBJECTIVELY better, spend your money elsewhere.


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## bxr140 (Jul 18, 2002)

*Re: Corrado single piston and Audi dual piston brake weights (Todd_hyperformance)*


_Quote, originally posted by *Todd_hyperformance* »_A two piston caliper is going to generate more clamping force because it is more efficient. It spreads more pressure over a larger area, allowing less pad deflection, better using all of the available pad.

this is a prime example of facts which are completely true, used incorrectly to justify something. a more effiecient caliper will absolutely generate clamping force more efficiently. it also MAY create less pad deflection, but that may not always be the case. however, in a REAL WORLD situation, the two piston caliper will NOT generate ANY MORE clamping force...see my above post. also, since friction has NOTHING to do with area, spreading "more pressure over a larger area" has no effect. in fact, if anything it will create MORE pad deflection, which contradicts your last point. 
you scoff at the 'theoretical' explaination, but then use 100% theory (incorrectly, i might add) in attempt to make your point. 

_Quote, originally posted by *Todd_hyperformance* »_Let describe it like this. Compare a bench vise to a c-clamp. If you use a 6" wide bench vise to compress something, using the same amount of force to turn the same dia and pitch of screw "all things being equal" you'll get a lot more clamping force from the bench vise. The vise is more efficient, it flexes less in the body and doesn’t deflect.

ever tried to use a bench vise NOT connected to a bench? not very effiecient. in any case, assuming the same contact area of the clamp and vise on your part, the clamping force will indeed be EXACTLY the same. do the math. numbers don't lie. flexing has nothing to do with the numbers, untill you exceed the capabilities of the material and it fails. you might need to turn the clamp in more to get that same force you 're turning the vise's screw, but thats NOT what you're talking about. 

_Quote, originally posted by *Todd_hyperformance* »_A larger pad is going to last longer, even if the annulus is the same, because of the way it deals with heat.

this is a very theoretical concept. when you consider the entire "thermal capacity" of the system, adding more material to the brake pad won't

_Quote, originally posted by *Todd_hyperformance* »_As far as performance, back then we didn't have measuring equipment, so I can spout any numbers, but the system performed extremely well at track days, and in real world situations, it did out perform the OE system. 

quite the quandry. it worked better, but you can't prove it. hmm....
also, there is a HUUUUUUUUGE difference between performing "extremely well" at track days and in real world situations, and perfoming "better" in those situations. nobody will argue that the dual piston caliper isnt a very capable part. 
i can see another problem here. the OE system DOES have weak links, and there are MANY ways to overcome these weak links. for instance, pad fade is usually a problem. one way to overcome the problem is to increase the "thermal capacity" of the system, by increasing the size of the components. you might get 20-30% more capability there, due to the increase mass and surface area. unfortunately, now someone replaces their stock brakes with big brake upgrade that eliminates the fade, and they proclaim the stock system is inadequate. 
on the flip size, if one simply changed their pad material to a performance material, one would have DOUBLED the thermal capacity of the system, and they would find the system to be much more than adequate. 

_Quote, originally posted by *Todd_hyperformance* »_As far as the potential clamping force of multi piston calipers being irreverent,







. That’s the whole point of a using them. That’s the reason audi put them on the 200 in the first place. Force and rigidity are the major factors that separate calipers in there performance. Why does Porsche...

whoa dude...youre changing the subject and youre using apples to justify oranges. youre making up a new argument here that more rigid calipers are more efficient, but i never said anything to the contrary. my point is that efficiency has NOTHING to do with the maximum performance of the caliper, which both of us were measuring as clamping force. we're also assuming you can stay within the structural constraints of the caliper, and the system can provide the caliper with an excess of pressure to overcome the tires. p-car's don't use VW brakes becuase the net result of their braking systems far exceeds that of the VW system. 

_Quote, originally posted by *Todd_hyperformance* »_ You keep talking like what your saying is gospel, but don't present facts to back it up. I'm presenting fact and opinion based on real world situations, not JUST theoretical. 

huh? theory IS fact, when presented locically and correctly, of course. and what have YOU presented that "backs up" your claims? absolutely nothing except speculation. if you can't explain something with theory, then all you have is speculation. not to mention that you're using theory (flawed theory at that) to attempy to justfy your claims.


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## vdubjb (Feb 18, 2000)

*Re: Corrado single piston and Audi dual piston brake weights (Skaven)*

Test the distances or forget it all.


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## bxr140 (Jul 18, 2002)

*Re: Corrado single piston and Audi dual piston brake weights (vdubjb)*


_Quote, originally posted by *vdubjb* »_Test the distances or forget it all. 

or fade resistance.








and make sure you've got all the variables under control...


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## Skaven (Nov 17, 1999)

*Re: Corrado single piston and Audi dual piston brake weights (bxr140)*


_Quote, originally posted by *bxr140* »_
or fade resistance.










Which is exactly the point. Why do people upgrade to the 11" brakes to begin with? They can reach that magical torque value (lock up) with their 9.4" brakes. So by adding the 11" rotors and caliper assembly all they are doing is adding unsprung weight, right? Since we know that the tires are the limiting factor, braking distance should be the same between ALL the braking systems, right? (assuming they are all capable of reaching the lock up torque value) So why upgrade?
*HEAT.*

_Quote, originally posted by *Pulp Friction* »_
So, Why Would Anyone Want to Modify Their Brakes? 
2) Thermal control: Modifying your brake system mass (rotor weight) can be used if there is a thermal concern in the braking system. If your brakes work consistently under your driving conditions, then adding "size" to the braking system will accomplish nothing more than increasing the weight of your vehicle. But if high temperatures are having an adverse effect on braking system performance or other components in general--wheel bearings, for example--then you should consider super-sizing. Of course, brake cooling ducts can really help out here as well. 

3) Temperature sensitivity: Modifying your brakes to address the presence of high temperatures (brake pad material and brake fluid composition) should only be considered if your thermal concerns cannot be resolved by super-sizing. This is really just a Band-Aid for undersized systems, like those found on Showroom Stock race cars that are not permitted by their rules to upsize or cool their brakes. One might argue that it is more cost effective to install better brake pads and brake fluid than it would be to upsize the rotors, but all that heat still needs to go somewhere--and more often than not it will find the next weak link in the system. 


_Quote, originally posted by *bxr140* »_
i can see another problem here. the OE system DOES have weak links, and there are MANY ways to overcome these weak links. for instance, pad fade is usually a problem. one way to overcome the problem is to increase the "thermal capacity" of the system, by increasing the size of the components. you might get 20-30% more capability there, due to the increase mass and surface area. Unfortunately, now someone replaces their stock brakes with big brake upgrade that eliminates the fade, and they proclaim the stock system is inadequate. 
on the flip size, if one simply changed their pad material to a performance material, one would have DOUBLED the thermal capacity of the system, and they would find the system to be much more than adequate. 

So taking both things into account; 20-30% more thermal capacity due to increased mass and surface area of bigger components and in addition to that you can get the SAME pad material that you claim doubles the thermal capacity. By doing both you have MUCH more thermal capacity! Which is what brake upgrades are all about. 
You can't stop the car any faster "all things being equal" - but you can increase the thermal capacity of the system to make *consistent consecutive* stops. After all - thats the whole reason in going to the bigger rotors to begin with!


_Modified by Skaven at 9:15 AM 6-12-2003_


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## Skaven (Nov 17, 1999)

*Re: Corrado single piston and Audi dual piston brake weights (Skaven)*

Another great article on Balancing Brake Upgrades. Tuning your brake upgrade is essential to stopping more consitantly!
Something I had not considered:

_Quote, originally posted by *Balancing Brake Upgrades* »_With bigger rotors, you can generate maximum braking force with less pedal pressure, less pedal travel, and therefore less time. It's this reaction time and the faster ramp up of the torque applied at the tire that creates the shorter stopping distances. When you're traveling at 60 mph, you travel 88 feet per second. If your brakes reached peak torque .1 seconds faster, then you just reached limit braking 8.8 feet sooner. So in that respect, bigger brakes can shorten braking distances. Another way brake upgrades feel better on the street is that the bigger rotor will generate greater torque for a given brake pedal pressure. Therefore, the driver can press lighter on the pedal to get equivalent stopping power. It feels like the brakes make a big improvement in stopping power -- but they really don't. You just don't have to push as hard to get the same power.



_Modified by Skaven at 9:29 AM 6-12-2003_


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## bxr140 (Jul 18, 2002)

*Re: Corrado single piston and Audi dual piston brake weights (Skaven)*


_Quote, originally posted by *Skaven* »_Why do people upgrade to the 11" brakes to begin with? They can reach that magical torque value (lock up) with their 9.4" brakes. So by adding the 11" rotors and caliper assembly all they are doing is adding unsprung weight, right? Since we know that the tires are the limiting factor, braking distance should be the same between ALL the braking systems, right?

that is a VERY valid question. in fact, for MOST people on the street, the 9.4's really ARE an acceptable brake setup, with good pads and fluid. that includes both braking power as well as fade/consistency. for many people, they indeed ARE "just" adding unsprung weight with upgrades. 
the other reason you might want to upgrade your brakes is that you may indeed NOT be able to generate enough clamping force at the caliper. this is not the case for almost alll VW brakes on the street, and most VW's even in track/heavy use situations. that is, once you upgrade the pads and fluid of course. 

_Quote, originally posted by *Skaven* »_So taking both things into account; 20-30% more thermal capacity due to increased mass and surface area of bigger components and in addition to that you can get the SAME pad material that you claim doubles the thermal capacity. By doing both you have MUCH more thermal capacity! Which is what brake upgrades are all about. 

very true, and another very valid point. however, at some point you end up over engineering the system. if the stock system ponly fades in very extreme situations (which SHOULD be the case), you can upgrade a few things to push you over the edge, right? say that 20-30% from the size upgrade gets you there. thats great. say the 80-100% from just pads and fluid get you there too. good. but say you do the size upgrade and ALSO pads. youre only adding potential, not anything real, since you could have "gotten there" with just the size upgrade. if you have 90%, and can only use 100%, adding 20% from the size AND 80% for the pads just gets you another extra/useless 90%. in that respect you just wasted your money, and have negatives to deal with to boot, such as more unsprung and rotational mass. 

_Quote, originally posted by *Skaven* »_You can't stop the car any faster "all things being equal" - but you can increase the thermal capacity of the system to make *consistent consecutive* stops. After all - thats the whole reason in going to the bigger rotors to begin with!

thats true, only if the thermal capacity of the system is the weak point to begin with.


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## Skaven (Nov 17, 1999)

*Re: Corrado single piston and Audi dual piston brake weights (bxr140)*


_Quote, originally posted by *bxr140* »_
say you do the size upgrade and ALSO pads. youre only adding potential, not anything real, since you could have "gotten there" with just the size upgrade. if you have 90%, and can only use 100%, adding 20% from the size AND 80% for the pads just gets you another extra/useless 90%. in that respect you just wasted your money, and have negatives to deal with to boot, such as more unsprung and rotational mass.

Its not another "extra/useless 90%" - its MORE thermal capacity. Lets say before the upgrade it took 4 60-0mph stops for the brakes to start fading. You are at the 100% thermal capacity within 4 stops. When you add more thermal capacity to the system - it will take LONGER to reach that 100%.

_Quote, originally posted by *bxr140* »_
thats true, only if the thermal capacity of the system is the weak point to begin with. 

If with upgraded pads/fluid/lines the Corrado brakes NEVER fade - then I agree, the dual piston calipers could be overdoing it. If they do fade, thermal capacity IS the weak point.


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## bxr140 (Jul 18, 2002)

*Re: Corrado single piston and Audi dual piston brake weights (Skaven)*


_Quote, originally posted by *Skaven* »_Its not another "extra/useless 90%" - its MORE thermal capacity. Lets say before the upgrade it took 4 60-0mph stops for the brakes to start fading. You are at the 100% thermal capacity within 4 stops. When you add more thermal capacity to the system - it will take LONGER to reach that 100%.

right, and anything above that 100% is, for lack of a better word, useless. thats exactly what i'm saying.

_Quote, originally posted by *Skaven* »_If with upgraded pads/fluid/lines the Corrado brakes NEVER fade - then I agree, the dual piston calipers could be overdoing it. If they do fade, thermal capacity IS the weak point.

lucky for you, that IS the case. my porker vr6 corrado with stock brakes, save for R4S pads and super blue fluid, will turn ALL FOUR rotors BRIGHT ORANGE hot (not just a dull red glow) with NO fade and NO decrease in pedal consistency. potenza S03 tires. you've got 400 pounds in hand with your car. stopping won't be a problem. lock up will.


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## Skaven (Nov 17, 1999)

*Re: Corrado single piston and Audi dual piston brake weights (bxr140)*


_Quote, originally posted by *bxr140* »_
right, and anything above that 100% is, for lack of a better word, useless. thats exactly what i'm saying.


There is nothing above 100% - I'm not sure if we are on the same page here.

_Quote, originally posted by *bxr140* »_
lucky for you, that IS the case. my porker vr6 corrado with stock brakes, save for R4S pads and super blue fluid, will turn ALL FOUR rotors BRIGHT ORANGE hot (not just a dull red glow) with NO fade and NO decrease in pedal consistency. potenza S03 tires. you've got 400 pounds in hand with your car. stopping won't be a problem. lock up will. 

Thats good to hear! Can you give me more info on your brake setup? Do you street the R4S pads as well (would those pads work on my 'rado brakes)? OEM rotors?
One more question. Is your stopping distance the same after those rotors are "orange hot" as when they are mildly warm?


_Modified by Skaven at 4:31 PM 6-12-2003_


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## bxr140 (Jul 18, 2002)

*Re: Corrado single piston and Audi dual piston brake weights (Skaven)*


_Quote, originally posted by *Skaven* »_ Can you give me more info on your brake setup? Do you street the R4S pads as well (would those pads work on my 'rado brakes)? OEM rotors?








that IS on the street! LFB really works the brakes...both ends...
i own a motorycycle, so spending money to put this car on the track is a bit...pointless.








in any case, yes, the rest of the system is (or was, in the case of my 93 C, which exhibited the same properties as my current 92) from the factory, except for the pads and fluid, and the rotors were OEM replacements. i've got a set of stainless lines i'll eventually put on the 92, but more for the sake of replacing the old lines, not becuase SS lines are god's gift to braking. 

_Quote, originally posted by *Skaven* »_ Is your stopping distance the same after those rotors are "orange hot" as when they are mildly warm?

well, since stopping your car on glowing rotors isnt the best idea, i've never done a proper distance measurement. sorry. unofficial "brake at this tree" tests, yes (which give the nod to the hotter setup) but nothing more objective than an eyeball "made it to this rock or that rock" measurement. 
supporting those unofficial tests, from my experiences driving the same road home from work ~2-3 times a week for the better part of a year and a half (in other words, i know the road and i know how i drive it), i've found that the hotter the *brakes* are, the more they SEEM to bite, and the faster they SEEM to slow the car. not by leaps and bounds, but i definately can go go deeper with my braking points and lighter on the LFB the hotter the brakes get. if i turn around halfway and go back to the start (in other words, a back to back "road test"), i do have a noticible increase of maximum braking power. i also don't know if its a linear relationship to heat or not, beucase its difficult to tell just how hot your brakes are on every corner. in situations where i figure the brakes would be the hottest, they SEEM to drop a heavier anchor. at some point, i'm sure there is a "too hot" pad condition (fade) but i know at least *I* can't get my brakes that hot. 
also, note that i can't PROVE that the *brakes* actually work better the hotter they get, because there are other uncontrolled variables. most notably, the tire temps. naturally, as i'm increasing the brake temps (braking hard, LFB), the tires are also certainly getting worked. to a point, hotter tires are stickier tires. while i definately get better *overall* braking with higher temps, i can't say if thats due to the tires, pads, or (most likely) a combination of the two. 
i have also overheated the tires (not on a road, but at an autox) and that definately was a disadvantage. since it WAS an autox, the brakes were getting relatively light work at relatively low speeds (never out of second). couple this fact with the siatuations i described above, and i would *speculate* that the brakes do indeed work better the hotter they get. i have not overheated (faded) the pads, but i don't know how much hotter you can get than BRIGHT ORANGE in the daytime....without melting stuff at least. 
off the subject, but an interesting data point nonetheless...this same road has some very bumpy braking zones. when my tires are worn, i get noticibly better traction through these areas. when i have newer tires, i need to brake earlier and pretty much count on the ABS to help out when the tires do lose traction. one of the biggest factors to this phenomenon? unsprung weight. worn tires weigh quite a bit less than new ones...


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## GTIRACER2.0t (Aug 23, 2000)

So after all the arguing..if you have both calipers, as i do, Girlin54's and 60's, is it worth it to use them and gain 12lbs for just upgrade the pads on the 54's?


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## bxr140 (Jul 18, 2002)

*Re: (GTIRACER2.0t)*


_Quote, originally posted by *GTIRACER2.0t* »_So after all the arguing..if you have both calipers, as i do, Girlin54's and 60's, is it worth it to use them and gain 12lbs for just upgrade the pads on the 54's?

is it "worth it"? all the information you need to make a logical and informed descision is presented above. to summerize, if youre looking purely for the best overall performance (braking, handling, etc.), you're better off with the single piston calipers. if you like the way the bigger calipers look (very few people will argue that biggger is not cooler), go with the dual piston calipers, cause they won't be THAT different. 
since i make a point not to tell people what to do (it *IS* your car and not mine, afterall), i'll let you make your own descision based on YOUR wants/needs.


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## GTIRACER2.0t (Aug 23, 2000)

*Re: (bxr140)*

Im function over form anyday. I want the best performance with stoping and handling. Dual piston may look cook but for extra weight and no extra stopping i dont need them. Some good pads and fluid for my g60's is all i need then


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## THE red rocket (Aug 16, 2002)

*Re: (GTIRACER2.0t)*

If you are coming up to the autotech BBQ/sale you can take my car for a spin with the duals and cheap ass metalmasters http://****************.com/smile/emthup.gif


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## ptgdudley (Apr 24, 2002)

To all posters above. I have enjoyed the postings. I have recently purchased the 13" wilwood kit from RPI for my 337. When people ask "why" I say because they are light weight! And they make pad changes a breeze. My factory brakes are excellent, even on the track & I have no complaints about them. But lighter (calipers) & easier (pad replacment) sound great to me. I can't wait to install them.
ptgdudley


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## GTIRACER2.0t (Aug 23, 2000)

*Re: (THE red rocket)*

Thats cool Andy , Ill be there..Thing is i used to have a A2 with g60's. The brakes were so great to me cause the car is so light. But ill see how yours feel..Do you take your car to any track events with that set up?
_Quote, originally posted by *THE red rocket* »_If you are coming up to the autotech BBQ/sale you can take my car for a spin with the duals and cheap ass metalmasters http://****************.com/smile/emthup.gif


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## 130_R (May 24, 2001)

*Re: (GTIRACER2.0t)*

I have the dual pistons, and they are worth it. 
If you think for a second that 6 lbs additional unsprung weight is noticable then you really need to re-examine the stock VW front suspension again. The deflection within the stock rubber suspension bushings make the suspension sloppy in terms of sensitivity and reaction speed and the suspension is not stiff enough within the upright assembly for the addtional weight to transfer into a large change in overall suspension performance.
In a nutshell, as long as you increase pad size and keep fluid pressure constant, braking efficiency will increase. The larger pad improves heat dissapation due to the larger trasnfer surface and decreases temperature buildup be cause the heat radiation surfaces are larger.


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## bxr140 (Jul 18, 2002)

*Re: (130_R)*


_Quote, originally posted by *130_R* »_If you think for a second that 6 lbs additional unsprung weight is noticable then you really need to re-examine the stock VW front suspension again..

uhh....you bolt a 5# weight onto your steering knuckle and you tell me if you feel a difference. like i said, the average driver probably WON'T notice the extra weight, even in a 'performance' situation. like i also said, the average driver probably doesn't have the skills to warrant whatever performance boost they think theyre getting. 

_Quote, originally posted by *130_R* »_In a nutshell, as long as you increase pad size and keep fluid pressure constant, braking efficiency will increase.

key word here is EFFICIENCY, not overall performance. in the end, youre still using a heavy floating caliper.


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## 130_R (May 24, 2001)

*Re: (bxr140)*


_Quote, originally posted by *bxr140* »_
uhh....you bolt a 5# weight onto your steering knuckle and you tell me if you feel a difference. like i said, the average driver probably WON'T notice the extra weight, even in a 'performance' situation. like i also said, the average driver probably doesn't have the skills to warrant whatever performance boost they think theyre getting. 

You are the one person on the earth that can feel the difference 6 pounds makes through three squishy rubber bushings, you my friend are special. Though I do admire your championing of the whole unsprung wieght mantra, you do realize that everything is a tradeoff when it comes to road going cars. If it means that I need to use heavier calipers to slow down faster, so be it. But you know, if you are so worried about that six pounds, change over to 10.1 brakes and remove 10 pounds of rotating disk wieght, that carries an exponetially worse wieght and mass penalty that any caliper or unsprung wieght.


_Quote »_
key word here is EFFICIENCY, not overall performance. in the end, youre still using a heavy floating caliper. 

Last time I checked, brake performance is directly realted to how *efficient*ly it changes rotating motion into dissapated heat.


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## bxr140 (Jul 18, 2002)

*Re: (130_R)*


_Quote, originally posted by *130_R* »_You are the one person on the earth that can feel the difference 6 pounds makes through three squishy rubber bushings, you my friend are special. 

uhh...
again, some will feel the weight, most will not. if you can't, then by all means, start packing on that extra weight. 

_Quote, originally posted by *130_R* »_Though I do admire your championing of the whole unsprung wieght mantra, 

i'm not champinoning unsprung weight as much as i'm champioining against UNECESSARY weight. if i was championing unsprung weight, i'd be suggesting everyone dumps their stock calipers for a set of wilwoods. 

_Quote, originally posted by *130_R* »_you do realize that everything is a tradeoff when it comes to road going cars. 

exactly. thats been my point the whole time. 
and if i may be so bold, it appears as though YOU need to realize that there are limits to road going cars. 
that, and the whole "overenginnering" factor.

_Quote, originally posted by *130_R* »_ If it means that I need to use heavier calipers to slow down faster, so be it. 

mileading information. 
you'll slow down faster with the same pedal pressure, thats certainly true...

_Quote, originally posted by *130_R* »_ if you are so worried about that six pounds, change over to 10.1 brakes and remove 10 pounds of rotating disk wieght, that carries an exponetially worse wieght and mass penalty that any caliper or unsprung wieght.

A) what does this have to do with what i have on my car? i'm simply presenting information to those who wish to take it. if you feel as though something i've said is incorrect, feel free to correct me. if you cannot find anything to correct, don't make the feeble attempt at changing the subject. 
B) i would hazard a guess that a 10.1" rotor is NOT 5# lighter than 11" rotor. 
C) i'm fairly certain i'm fairly close to the limits of my brakes, as far as heat is concerned. i don't want to spend the money to swap out parts only to find they are not adequate for my application. 
D) whats the difference between a weight and a mass penalty?
E) back up your "exponentially worse" statement. if you can't, thats just another example of those who don't/can't/won't understand spinning the discussion...

_Quote, originally posted by *130_R* »_Last time I checked, brake performance is directly realted to how *efficient*ly it changes rotating motion into dissapated heat.









forgive me, i should have clarified. ULTIMATE braking performance. unless heat is the weak link in the system, the system can be as efficient or inefficient as it wants. and in most cases, providing you stay within the heat limitation of the pads, your system will be MORE efficient the HOTTER it gets. 
and finally, lets remember that we're still talking about floating/one sided calipers here...


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## 130_R (May 24, 2001)

*Re: (bxr140)*


_Quote, originally posted by *bxr140* »_
mileading information. 
you'll slow down faster with the same pedal pressure, thats certainly true...



Thank you, you just proved my entire point, dual piston brakes make you faster!








As for the rotating mass argument, adding one pound of rotating mass adds one pound of scalable wieght and a quarter pound of effective mass (mass penalty). The rotating force increases as a square of the acceleration, not a linear value of accleration.


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## bxr140 (Jul 18, 2002)

*Re: (130_R)*


_Quote, originally posted by *130_R* »_Thank you, you just proved my entire point, dual piston brakes make you faster!







.

actually, i just proved that you have no foundation for your points. 

_Quote, originally posted by *130_R* »_As for the rotating mass argument, adding one pound of rotating mass adds one pound of scalable wieght and a quarter pound of effective mass (mass penalty). The rotating force increases as a square of the acceleration, not a linear value of accleration.

its not that easy. side stepping the whole weight vs. mass thing (i'll admit, it was kindof a trick question) you can't just put numbers onto the extra mass without more information. one pound mass = 1/4 pound "effective" mass...not sure what you're trying to say here. in any case, its fairly easy to explain intuitively, but a bit more complicated when you start to talk numbers. 
the jist of the matter though, is that the added mass has two effects (the commonly referred to "unsprung" and "rotating"), and the magnitude of those effects depends on both the amount of mass added, as well as the position. for unsprung mass, the farther away from the control arm pivot axis, the more noticible the effect. if you bolt that 5 pound weight onto the control arm, you will notice it less than if you bolted it onto the outside of the wheel. however, since you really only can add/subtract mass from the wheel, tire, rotor, or caliper, ALL which are *about* the same distance from the control arm pivot, their associated forces (from the suspension moving up and down) can all be scaled pretty much the same way. in other words, if you add 5 pounds to the tire, or 5 pounds to the caliper, you can basically assume the mass will have more or less the same effect. of course, the nature of dyamnics is much more complicated than that (coupled with the changing suspension geometry) but using the above assumptions will get you pretty damn close. 
rotating mass, however, depends GREATLY on where it is added or subtracted. for instance, if you add 2 pounds to your rotor, that will have less effect than 2 pounds to your tire. how much of an effect depends greately on WHERE the mass is added, even within the component, so as a general rule, its best to just go with the simple but effective "the farther away the mass is from the rotation axis, the worse its effect will be".


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## 130_R (May 24, 2001)

*Re: (bxr140)*


_Quote, originally posted by *bxr140* »_
actually, i just proved that you have no foundation for your points. 


Actually, I don't think you realize you keep telling me I am wrong with out putting forth any evidence that adding 6 pounds of unpsrung wieght is more detrimental than decreasing your stopping distances by 15%.


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## PowerDubs (Jul 22, 2001)

*Re: (130_R)*


_Quote, originally posted by *130_R* »_
Actually, I don't think you realize you keep telling me I am wrong with out putting forth any evidence that adding 6 pounds of unpsrung wieght is more detrimental than decreasing your stopping distances by 15%.











Well, I accelerate a whole lot more than I am ever on the brakes hard.... most of the time I use my brakes sparingly, and let the engine control my speed....habit from all my years of motorcycles.... so at least for me, I would use the accel and handling from the less weight more than I would use the max braking ability from the heavier brakes.


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## bxr140 (Jul 18, 2002)

*Re: (130_R)*


_Quote, originally posted by *130_R* »_Actually, I don't think you realize you keep telling me I am wrong with out putting forth any evidence that adding 6 pounds of unpsrung wieght is more detrimental than decreasing your stopping distances by 15%.


















i guess i must have missed the part where you proved the calipers decreased your stoipping distances by 15%...
tell you what, go ahead and rearead the thread. oh, and don't worry, i'll let you smack yourself in the privacy of your own home.


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## fluxburn (Sep 23, 2002)

*Re: (bxr140)*

Here is a simple question, do these bolt up to a mk3 2.0? Much better than my brakes lol!


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## Skaven (Nov 17, 1999)

*Re: (fluxburn)*

They will bolt up to a MK3 with the 10.1" brakes. You WILL need the Corrado G60 rotor as well. http://****************.com/smile/emthup.gif


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## PowerDubs (Jul 22, 2001)

*Re: (Skaven)*


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## 130_R (May 24, 2001)

*Re: (PowerDubs)*


_Quote, originally posted by *PowerDubs* »_









You think I forget.


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## wjbski (Feb 1, 2003)

*Re: (130_R)*










while everyone seems to have good points in the debate, will someone go to a track and produce some *hard data* ?


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## bxr140 (Jul 18, 2002)

*Re: (wjbski)*


_Quote, originally posted by *wjbski* »_








while everyone seems to have good points in the debate, will someone go to a track and produce some *hard data* ?

and don't forget to account for ALL of the variables in the results! http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif 
we don't want 130_R to smack himself again, afterall.


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## jamesn67 (Nov 15, 2001)

*Re: (bxr140)*

Hmmm. very interesting thread. I'll have to sit down and think about the physics
of it. No question easiest thing is to test the two brake set ups on the same car
keeping as many of the variables the same. And the more data points you have
the better you can rely on the results.
I do not really know much about these calipers aside from one having a single piston and the other two. What is the area of the single vs. the double(total)? Even
if they have the same area(total), thereby creating the same force for the same pressure
(assuming all else is the same) the force distribution on the pad will be different.
The double unit would spread the load out over the pad area, thereby increasing
the working area of the pad which would distribute the heat over more of the pad.
However, this gets more complicated because I assume the pads are different.
So I am not sure you can directly compare the two. But, the idea of more pistons
is to have a more even distribution of pressure over the pad thereby spreading out the heat more evenly. Without thinking some more I won't say if that would make
a measurable difference. Would obviously depend on the set-up of the two systems. (I have neglected to include any equations for this. I can include them
if anyone cares. They are very simple)
As for flexure of the caliper, that might make some difference, but with the caliper designs being different it is hard to say which might flex more. 
I am also curious as to why the dual piston version weighs so much more?
Do the porsche model weight a lot? I am thining not, but I am sure they cost
many times more. 
With regards to rotating mass btw... the equation is mass*radius*omega**2
So, yes the further you are away from the center of rotation the greater the
force.
I am sure there are some issues with moments (force*distance) about the suspension components but I am not sure of the effect without really sitting
down and trying to come up with a diagram of the forces in the system.
Now for my question...I am going to be putting 11" brakes on my mkII GTI and
there seem to be so many different single piston OE versions that appear to
fit. For instance etka lists the 1990 corrado as having two different caliper/carrier set-ups. I guess there was a mid-year model switch or something. Anyone know what differences there might be in them and if any are better
than any of the others? 
Thanks for the fun!


_Modified by jamesn67 at 1:22 AM 8-1-2003_


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## Skaven (Nov 17, 1999)

*Re: (jamesn67)*

The only difference I can think of between the two Corrado G60 calipers is that one may be for an ABS equipped car and the other for non-ABS cars?


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## jamesn67 (Nov 15, 2001)

*Re: (Skaven)*

Thanks!
Just another interesting fact...it seems that the R32 fronts are dual piston calipers. At least
that is what the site selling them claim. 
I'll bet you did not epxect your question to turn into this long debate. 
If you actually do both I'd love to know your opinions. 
Thanks!


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## Skaven (Nov 17, 1999)

*Re: (jamesn67)*

I'd be happy to do both. But I would have to get the same type of pads for both sets of calipers = $$$. It would also be almost impossible to account for all of the variables without expensive equipment...
I'm afraid that me and a g-tech probably wouldn't cut it.


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## askibum02 (May 10, 2002)

*Re: (Skaven)*

I may have missed something here, and I definately suck at physics, but this is my question. If there is no advantage to the dual piston calipers, why did Audi make the switch from the single to dual piston caliper in the first place. They were using the Girling 54 in all there cars and deemed it not adequate enough for the 5000. You would think that if a dual piston caliper is used to stop a heavier car faster, or even on par with a lighter car, that the braking system has *some * advantage. That advantage would be multiplied by a car that weighs less. Just my .02. http://****************.com/smile/emthup.gif


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## PowerDubs (Jul 22, 2001)

*Re: (askibum02)*

I don't think the arguement was over the improvement itself....but if it was enough improvememnt to justify the weight penalty, and the exceeded threshold factor. If 10's or 'normal' 11's brake fine for a 2400 pound car, 13's would serve no useful purpose. 
Think of it this way... if your car gets good traction on 205 tires (no spinning) then there would be no need for 245 (?) tires... sure you could say they 'have' more traction *capability*....but in reality the usefulness in YOUR situation would be nil, and the weight and increased steering effort would make for a bad choice.


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## bxr140 (Jul 18, 2002)

*Re: (jamesn67)*


_Quote, originally posted by *jamesn67* »_ Even if they have the same area(total), thereby creating the same force for the same pressure (assuming all else is the same) the force distribution on the pad will be different.The double unit would spread the load out over the pad area, thereby increasing the working area of the pad which would distribute the heat over more of the pad.

kinda. the distribution will be different, but not necessarily better or more consistently. either way, the point is moot, as the backing plate of the pad indeed spreads the force of the piston over the entire pad area. if you made a thermal image of a pad in any setup, i'm guessing the general temerature trend across the pad will be nearly identical in all situations. 

_Quote, originally posted by *jamesn67* »_ I am also curious as to why the dual piston version weighs so much more?
Do the porsche model weight a lot? ]

quite simply, the dual piston is alot bigger. its got more material to cast two cylinders instead of one. 
the porsche calipers are NOT to be compared to the audi calipers. the audi calipers are still a floating design, which inherently has much more flex and inefficiencies than a fixed caliper design, like the p-car. compare the porsche brakes to stop-techs, willwoods, etc. they are a different animal. for reference, the standard wilwood dynalites are a fixed 4 piston caliper, and they weigh like 3-4 pounds each. they also cost like $120 or less each. 

_Quote, originally posted by *jamesn67* »_ I am sure there are some issues with moments (force*distance) about the suspension components but I am not sure of the effect without really sitting down and trying to come up with a diagram of the forces in the system. 

its really more to do with the force/mass/damper system. i brought up the whole distance away from the control arm pivot thing to explain a lesser effect of less unsprung weight, but in reality, all of that weight acts at more or less the same point, whether its the wheel, rotor, caliper, or tire. with the F-M-D system, if you keep the force constant (if your car hits a pothole at X speed, the force translated into the suspension is always going to be the same) and the damper the same (the damping rates of the struc/shock stay the same), decreasing the mass of the system will increase the accelerations. increasing the accelerations means the suspension will move up and down faster, and as such it will maintain more constant contact between the road and the tire.


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## jamesn67 (Nov 15, 2001)

*Re: (bxr140)*


_Quote, originally posted by *bxr140* »_
kinda. the distribution will be different, but not necessarily better or more consistently. either way, the point is moot, as the backing plate of the pad indeed spreads the force of the piston over the entire pad area. if you made a thermal image of a pad in any setup, i'm guessing the general temerature trend across the pad will be nearly identical in all situations. 


I am sure the distribution will be different. You are right though maybe not better.
It would depend on the size and placement of the dual pistons. However, I would
not be so sure the backing plate distributes the force out across the whold pad.
I have done many computer analyses of bolted parts and the contact distribution
is always pretty close to the bolt head even under high clamping loads. This is
backed up by wear marks on the components as well. There would definitely be
some dropoff not sure how much though, and maybe not enough to make a difference. Would make an interesting analysis. Maybe I'll try to put a model together next week. Then I could plot the force distribution, and assuming some
friction coefficient, calculate the heat flow pattern. Any idea what material the
backing plate is? Pistons? 
So the dual piston caliper is larger then? It does not necessarily have to weigh more though. Could use a different material, and if the pistons add up to the
single...but I suppose extra hardware and all...and the experience I have had
working with some car manufactures they did not seem to be very concerned
about weight. Usually more about cost. 
Those porsche and other calipers are fixed calipers then. Do they use a lighter
base material as well? Seems like the mkIV's are using aluminum, at least for the rear I believe. Just curious what those are made of. I have never really seen
the fixed ones up close. 
True enough about the suspension responding quicker to the lighter car. You wonder though at what threshold does the weight change actually begin to make
any appreciable impact. Would be related to the sensitivity of the shock/spring
set up I suppose. 
Definitely a fun thread though. Thanks everyone.


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## bxr140 (Jul 18, 2002)

*Re: (askibum02)*


_Quote, originally posted by *askibum02* »_If there is no advantage to the dual piston calipers, why did Audi make the switch from the single to dual piston caliper in the first place.

ahh...the cardinal sin of automobile modifications..."if MUST be good for MY car if the factory put it on THAT car."
one might then suggest (and more than one has, in the past) that drilled rotors must be good because porsches come with them from the factory. 
ever look at a porsche race car? 
anyway, back to the point, audi likely deemed them inadequate for the 5000, most likely because they found that the 54's were lacking with one or more of the characteristics on the 5000. no more, no less. my guess is that it was due to the weight of the 5000. 
as we've said time and time again though, if your brakes can consistantly exceed the capabilities of the tires without fade or a change in pedal feel, what advantages do you have to gain?


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## bxr140 (Jul 18, 2002)

*Re: (jamesn67)*


_Quote, originally posted by *jamesn67* »_ However, I would not be so sure the backing plate distributes the force out across the whold pad. I have done many computer analyses of bolted parts and the contact distribution is always pretty close to the bolt head even under high clamping loads. 

indeed. a bolt is not quite as big as a piston, however. 
regardless, i've never taken a set of pads off of a car that are noticibly worn more near the piston contact area than the outer edges. in other words, the pad material wears at the same rate (or pretty damn close to the same rate) over the entire area of the pad. that would suggest that the temperature across the pad, as well as the pressure distribution across the pad are fairly constant. 
actually, i've noticed that if anything, the trailing edge of the pad gets worn the lease, and there is a constant increase of pad wear to the leading edge. 

_Quote, originally posted by *jamesn67* »_ So the dual piston caliper is larger then? It does not necessarily have to weigh more though. 

but thats the point. it DOES weigh more. we're talking specifically here between the G54 and G60 calipers. 

_Quote, originally posted by *jamesn67* »_Those porsche and other calipers are fixed calipers then. Do they use a lighter base material as well? 

most of the ones you'll see people bolting onto their VW's are cast or billet aluminum. check out the wilwood website...they've got a bunch of different calipers and a schpeil on each one. 

_Quote, originally posted by *jamesn67* »_True enough about the suspension responding quicker to the lighter car. You wonder though at what threshold does the weight change actually begin to make any appreciable impact. Would be related to the sensitivity of the shock/spring set up I suppose. 

its related to the sensitivity of the shock/spring setup in so far as the weight is PART of the shock/spring setup. youve got your spring, you've got your damper, you've got your mass (of that system) and you've got your external force. 
the only wrench in the plan is that the dynamic movement of the system screws up the geometry, and as such, makes characterizing the external force quite annoying. 
moot of course, as a lower system mass is always going to result in faster accelerations. faster accelerations equals smoother rides and more consistent traction.
at what point is the weight noticible? it depends. it depends on the circumstances, and it depends on the driver. on a smooth straight road, even the most skilled drivers would have a hard time noticing 20 pounds of difference. on bumpy roads, many drivers will notice 5 pounds of difference. i think its more about the percentage of change, rather than the amount of change. 


_Modified by bxr140 at 12:52 AM 8-3-2003_


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## jamesn67 (Nov 15, 2001)

*Re: (bxr140)*

And now that I think of it the contacts are quite different as a piston is a solid round
contact whereas the bolt head only contacts outside the shank. Ca't really compare
those. But you'll have some drop-off as you move away from the piston foot print,
but maybe it is only minor. 
I have seen some bolts however that were as large as these caliper pistons. Locomotive
application...16 cyl. massive engine. 
More wear on the leading edge of the pads then...I have to say I haven't really looked 
that closely at any of mine. When I take out my current ones I'll have to take a look.
But yours looked to have worn pretty evenly then? That would seem to suggest an
even distribution. Just curious, any idea what the thermal conductivity of the pads?
Just wondering about the heat paths in the parts. Never really thought about it before.
I understand the duals weigh more, was just saying that it inherently does not have to weigh more as those fixed caliper designs demonstrate. I'll check out their website for sure.

With regards to the weight impacting the suspension, what I was wondering was 
how much of a weight change is necessary for it to have any appreciable impact
on the handling. Obviously, a difference in weight means a difference in your
mass/damper system, but those spring rates are pretty high, so the deflection change
due to a small change in weight would be small. When would that change begin to really impact handling I wonder?. But, as you mention there are obvious dynamic issues that complicate matters. But I do agree, that for many reasons lighter is obviously better. 
Thanks!


_Modified by jamesn67 at 10:34 AM 8-4-2003_


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## Pagano (Sep 24, 2001)

*Re: (jamesn67)*

I just did this upgrade...or apparant downgrade as some of you see it
Base: 10.1" MK3 setup
Now: 11" Girling 60
Difference...Night/Day


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## bxr140 (Jul 18, 2002)

*Re: (Pagano)*


_Quote, originally posted by *Pagano* »_I just did this upgrade...or apparant downgrade as some of you see it
Base: 10.1" MK3 setup
Now: 11" Girling 60
Difference...Night/Day


A) youre not reading correctly. the upgrade, downgrade, or sidegrade everyone is talking about here is 11" w/ single piston to 11" w/ dual piston. especially on an A3, going from the 10" to 11" w/ dual piston is going to make a DRAMATIC difference, at least in the way it feels. i'd venture a guess that it would make a fairly sizable impact in the performance as well, most nobably in fade resistance and pedal consistancy. 
B) i sound like a friggin broken record, but observations (like your "Night/Day") mean absolutely nothing without information pertaining to the components before and after the swap. night and day feel? night and day performance? 
this is how misinformation gets spread around.


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