Bill Verburg

When comparing Big Reds to standard 993 brakes there are 3 separate but related characteristics of interest

1. thermal performance
2. brake torque
3. ergonomics

As to 1, there is no doubt that the larger rotors run cooler for a longer period of time, the net result is that they and associated components such as pads, seals and fluid will last longer. This characteristice is the primary reason most update to the Big Red package. Most any brakes can stop a car hard once, it takes something really special to do it from high speed over and over w/o degradation in performance or confidence. The Big Red pad is only incrementally larger than a stock 993 in front, and much larger in the back, this has the effect of spreading the reduced thermal load over a bigger area, further reducing all of the various stresses present.


As to 2, the larger rotors can generate greater torque when pushed hard, the limiting factor here is the tires, You guys brought up a really good point about the aero package and it's effect on braking performance. Usually when an upgrade to brakes w/ greater torque potential is made all the associated systems will also be upgraded, i.e. stickier tires, stiffer suspension, upgraded aero etc. All of these will influence the actual ability of the car to decelerate. The slave cylinder size of the Big Reds is the same as for a 993 in front and can be bigger or smaller in the back depending on whether 993tt or 993RS calipers are used.

for item 3 cooler brakes do feel better as long as they are in the operating zone of the pads, 993 tt rears will also provide a slightly higher harder pedal than stock, this is comforting, 993RS will povide the opposite, a slightly lower softer pedal. These are not big deviations from stock and are of little consequense. Ergonomics of any of theese systems are improved by using a bigger m/c, the reduced slave /master ratio is the sorce of higher, harder pedals, Porsche has always used a lower slave/master ratio in their sporting cars which is lower than in their more mundane offereings. for a 993RS this ratio is 16.8, for a normal 993 it is 18.7. Lower here will feel better and be easier to modulate. Again not necessary but very nice if you have it.

Cupcar

Speaking of the aero package and effect on braking perfomance.

It is had for me to understand how the F1 boys do it since the loss of downforce as they brake and slow the car has to be titrated off precisely during the braking.

At Monza they go from 335 to 115 Kilometers per hour in 100 meters as they go down from 6th to 2nd gear with their body against the seat belts at 4 G's all the while keeping the tires at the limit of adhesion as they lose 3000 pounds of downforce and trail the brakes into Variante della Roggia.

When Montoya was asked about it he said: "It's simple, hit the brakes at 100 meters and turn in".

I couldn't believe how he thought it simple.

Martin S.

The wing I am familiar with is the 993RS CS (Club Sport). It has multiple settings available from 0 dehrees of down angle to 9 degrees of down angle. At 9 degrees of down angle is where you get the maximum downforce at terminal velocity.

I had a knock off 993RS CS wing...it is in a new home in Sebring Florida. It too was adjustable, but it dod NOT have the side airscoops found on the 993 RS CS genuine factory tail such as Kary has on his car.

Kary writes, "....I am working on at my next track event in a week and half." Where are you going Kary? TracQuest Infineon is coming up...POC Thunder Hill is coming up in October...PCA Pahrump is coming up soon too...probably Pahrump...I can't get a pass. Wifey cracks the 50 barrier...she'll need emotional support.

And finally, Cupcar's Avatar, priceless! And the Montoya comment confirms to us mere mortals know that 99.9% of us are way, way down in the driving talent department compared to the F1 Masters.

I heard a comment about Willow Springs Raceway once that got me to thinking about my talent, or lack therof.....the Turn 8 sweeper, the fastest part of the course, into Turn 9 is nearly blind in a one sense...you can't really see the apex from the turn in point....one quick driver was supposed to have said (Urban legend?) when asked how he got through the turn so quickly...it's simple, brake as usual, enter the turn, get back on the gas, count to 4, and turn in..you'll hit the late apex required to make it through." Don't quote me on the seconds required, or for that matter the accuracy of the quote, nor the source...it does make for some great speculation though....I won't be trying this trick...don't try this at home!

And finally, the comments in this thread lead me back to Chris Walrod's inimitable words, "Is this a great place, or what?"

kary993

PCA SDR Pahrump event is October 1 and 2. Should be a great event as there are now four track configurations. The temperatures will be in the low 90's high 80's which will better than the summer event at willow when it was 104 both days!!!

Martin, bring the wife along, there is a big Rodeo there and gambling!!!

Martin S.

Oct. 2nd is wifey's birthday, the big 50. There is no way she will tolerate being stuck in Pahrump, on this holy day. I like the idea...but this is a sell I don't want to touch. Perhaps you can sell her for me????

TonyN

Yes, you did see them on the list. I'm selling my Big Red RS rear calipers. I'm selling the 993C2 with the Big Red brakes, so I'm just going to re-install the regular Big Red rear calipers. I installed them originally because I found that it was too easy to lock up the front Big Reds with the regular Big Red rears on the track. On the street it doesn't matter much. As Eric said, one has to either change the bias valve or the rear calipers in order to get the same balance on the C2 as the balance on the C4S/TT Big Red setup. PM me if you're interested.

Rob993

Martin: "Going faster with Bigger Brakes, I don't think so....and now that you are thinking I am insane, please read on."

Martin is wrong! The big reds are faster, er I mean they look faster

TonyN

I was wondering why you had that silly grin on your face all weekend<g>. So it was not just the opportunity to drive the GT, but that you had finally upgraded to the BR setup. I agree with you on your observation, but I would add that you may not feel the same way at a smaller track where the brake zones are not as long and where you don't have to brake as hard as at RA. But no question that the BR setup gives you more thermal reserve compared to the stock black calipers.

I must say that the C4S/TT setup gives one exceptional confidence and always makes you feel like you have "hands of God" brakes. It is possible to get the RS rears to lockup compared to the stock BR rear calipers on the 993c2, so one has to be careful in hard braking zones such as T5 or T12 at RA to keep the rear end from waggling. I never felt that with my C4S, and I was able to brake just as hard which I think is due to the 4wd, hi-pressure brake system, different MC and different bias valve. The BR setup with RS rear calipers comes very close and probably has more overall braking power due to the slightly larger rear calipers and the car being lighter, given a good driver. I can also get my GT3 to waggle it's rear end quite severely if I get on the brakes too hard, with the OEM pads.

Martin S.

Above we read, "because I found that it was too easy to lock up the front Big Reds with the regular Big Red rears on the track."

The last time I did any serious high speed work, was at California Speedway last yeat...2004. I have a 97 narrow body car with Big Reds from a 97TT car, thanks to the P.O.

Coming off the back straight the car was at about 130 to 135....needed to get hard on the breakes and down to second gear for a left turn in. I ran Pagid Black on the front, Pagid Orange on the rear and I believe Kumho Ecsta MX tires, shaved and heat cycled...believe me that I was hard on the brakes scrubbing off that much speed...we did this for 25 minute sessions.

At no time did the fronts ever lock up, nor the rears for that matter. I was pushing that brake pedal to the floor and letting the ABS do its stuff. I am thinking if you were locking up wheel(s), there may have been something amiss with the ABS...just my $0.02.

Rezal

I think Bill can correct me on this but if you have a TT or C4S, where the Big Reds came standard, your brake bias is set-up for the standard TT Big Reds F and R. If you have a C2, C4, or C2S, you will need RS rears to prevent the fronts from locking up. It has something to do with the brake MC. (As an asideI believe one is vacuum assist, the other hydraulic, tho I don't thing this is a factor).

I don't know how narrow body (or C2S) folks with TT rears do NOT have front lock up problems as the bias is clearly different. I personally experienced this with TT rears and the problem went away with RS rears. The TT rear set-up would lock up (actually, the ABS kicks in) even in normal driving conditions, more so in slippery conditions. My RS rear set-up has already survived several track days with no problems.

Yes, you can play around with different F & R pads like Martin but I don't want to spend $ on brake pads mucking around with different set-ups (tho I guess one could use Martin's set-up).

Here's a white paper written by someone more knowledgeable than me on brake bias, balance and optimization which I hope will settle this recurring argument:
http://stoptech.com/tech_info/wp_bra...formance.shtml

Bill Verburg

tt and C4 come w/ 28/28 rear calipers and 322x28mm rear rotors, comppared to the stock993 30/34 and 299x24mm rotors, the pistons on the tt/C4 move bias forward the rotors move it back, net result is a little more front than a stock 993, they can use it because of 2 things AWD and LSD both have the same effect as more rear bias.


993RS uses 30/36 on 322x28mm rotors w/ 40/60 acc/del lsd and relatively stickier rear tires. It has more rear bias than either 993 or tt/C4 but only under lightly loaded conditions. Extra rear bias in all of these cars is reduced by the p/v's under very heavy braking.

Martin S.

The POI of my car added the Big Reds...I don't know if he changed anything else. I'd have to have a Porsche Tech root around to find out. All I know is that the Big Reds work great with no apparent (to me) bias.

The car stops just fine with the following set ups: Pagid Black on Front/Pagid Orange on Rear, Pagid Orange front and rear, stock pads front and rear.

I have done some hard braking on the car at Streets of Willow with stock pads, a short course notoriously hard on brakes...the stock pads worked fine.

However for Cali Speedway, I go to Pagids...I also do the same at Laguna Seca and Infineon (Sears Point). At these tracks I am taking no chances that any fading can occur.

In closing, the StopTech article is very, very informative...and only further confirms what some of have been saying all along...it is your tires that are doing the most working stopping the car....size of the tire patch and the stickiness of the compound.

Bill Verburg

As Martin said the full 993RS f/r setup is great w/ stock p/v.

I have 2 cars w/ them now, the '76 Carrera hasn't got a p/v or ABS, the '95 has both stock p/v and ABS. Both have LSD and relatively large rear contact patches in the back. The Abs and p/v just give you more lattitude for foot error in very heavy braking.

Both use 23.8mm m/c, but the power in the '95 helps to get line pressures up w/o strain. Makes longer sesssions less wearisome.

Bill Verburg

Just as an aside, I also have a set of tt rears which I want to experiment w/. Just to see what the difference might be. Maybe next summer

TonyN

I did not actually mean "lockup", I meant "tires starting to slide which causes ABS to actuate". Of course one can use different kind of pads F+R to adjust bias, and also change the brake bias valve, but the 993RS rears provide more rear braking power and heat up the rear pads more. All 3 things can be changed to make adjustments. A number of threads have discussed this in great detail. I actually think that it is best and cheapest to change the brake bias valve if one had a box full of them, and had the time and skill to swap them out until you got it right. I did that with my race car, but as someone pointed out, the factory did most of that work for you with the 993RS calipers. I can testify and many others that the 993RS rear calipers provide better brake balance and more braking power for the 993c2 than the TT/C4S BR setup.

(I don't want to hijack this thread and discuss braking with the ABS or without, but my opinion is that one can and should brake harder by not actuating the ABS. When I get into the ABS under max braking conditions, the car actually speeds up a bit. Max braking is achieved by me on my cars by getting the tires to sing a bit without actually invoking the ABS. I only get into the ABS when I make a mistake, it's wet, or the friction coefficient of friction changes suddenly.)