Black Sea RD

Great suggestions on helping with the brake fade issues. I'll jump in with what I have learned playing on the track about my stock brakes (S4 style) on the 1986.5 track car.

I always change my brake fluid completely, front and rear, before every track day and I use a power bleeder. I use Valvoline "SYNPOWER" synthetic fluid that can be bought at just about any parts store. It's compatible with our ABS systems and has a very high wet boiling point, just a few degrees off from that fancy blue/gold brake fluid that, from what I understand, is not DOT approved for road use. I've never had an issue with brakes fading on me even on very hot Florida track days in July and August. This is the same fluid that was in the car when Mark A. ran it at the recent Sebring Club races. with no problems except for one problem I caused myself but which got better over a day of track use. Which was...

I changed both the rotors and brake pads (Pagid Orange front and rear) right before the races which Mark A. said should not be done since it takes time for the rotor and pad to work together to stop since no pad material was into the rotor. After the course of a day of run sessions the brakes got better and by the second day all seemed good.

I did have my brake master cylinder go bad and it presented with a soft pedal even after a full bleed. I would have to pump up the brake pedal a bit to have maximum firmness. I also noticed debris in the front caliper fluid when I changed the fluid. Brake pedal also would not hold firmness under constant pressure at a stop. I changed the brake master and all was set right again.

When intially going through the brake system after getting the car I wanted to put on the fancy SS lines. I did try to install a set but they were not fitting like the stock set would. After talking with Mark A. at 928 Intl. I decided to buy OE brake lines. The SS lines I'm sure will work but the OE lines are just more robust and I was told they are very strong compared to a SS set that have been known to break off at the crimp if the brake caliper's weight was placed onto the line by accident. Was told the OE lines would not do this. Never have had an issue with soft brakes except when I had the bad master problem.

I changed my brake bias module to a 33 bar. Even under hard braking and into ABS engagement no issues at all. Brakes feel very balanced. The car weight has been reduced to about 3000 lbs though.

HTH,
Constantine

Mike Simard

I second Constatine's fluid recommendation
I've tried many fluid types including Castrol SRF which is the only true high temp racing fluid. Another consideration should be the seal compatability. I used to have a car with a sleeve type throwout bearing that was very sensitive to seal swelling and lubricity, a great test bed! . Of the many fluids I tried Valvoline Synpower was the only one that allowed smooth travel thus implying good seal compatability and/or lubricity.

I also used it in my stock S4 on Hoosiers for a track day. Mine was one of the few cars that did not loose brakes and it was being driven very briskly. There are 2 other things important for brake non-boilingness:

1-Completely flush the fluid BEFORE AND AFTER a track day. Fluid collects water just being there day to day, that lowers it's boiling point daily just sitting around or driving gently. That's also the reason it's recommended to not use fluid on your shelf that was opened many moons ago.

2-When on track use the brakes harder for shorter intervals. Pretend that there's a clock with a given amount of time before the brakes boil once the pedal is applied, it doesn't matter if they're lightly applied or if you're standing on them.

SwayBar

Mark is correct. One other thing to do is correctly burnish the virgin rotors which includes a series of increasingly harder stops and letting the rotors cool down completely overnight before using them. A lot of cracked rotors are from thermal shock which burnishing helps alleviate.

Here is some in-depth info on the subject:

http://www.stoptech.com/tech_info/wp...contents.shtml

Best-case scenario is to have a brakepad/rotor combo for the street, and another brakepad/rotor combo for the track. The track combo should already have brakepds fully bedded-in on burnished rotors.

More kickass braking info here:

http://www.stoptech.com/tech_info/te...e_papers.shtml

Ed Hughes

My .02. With something like brakes and a track environment, you've not done things right. First, in our region of PCA, and I believe it's a National standard, it is required that brake fluid be no more than 6 months old to pass tech. I flush my brakes after every weekend, or should I say prior to every weekend. Cleanliness is next to Godliness. 14 month old fluid isn't good. As mentioned, ATE Super Blue or Motul RBF600 (better) are the ones to go with.

Secondly, if you have brake fade, which is usually caused by cooked fluid, you should've bled all 4 wheels, starting at the right rear (furthest) and ending at the left front (closest). Bleeding just the fronts was ineffective at bleeding a system.

928autobahndreamer

If there is a little sticking on one of the calipers is this something that can be freed up or is this a sign that the caliper needs to be rebuilt or replaced? Unfortunately I have noticed that under a hard panic stop that my car tends to be a little squirrley, pulling to the right. The wheel on that side does not spin as freely as the other. It stops after about half of a revolution where the other wheel spins more freely.

This may explain why I have not been impressed with my new S4s brakes. It sounds like they are not up to snuff. I have not yet replaced the brake fluid, but if I need to do a full overhaul, I may just try to do it all at once.

Ed Hughes

Could be a warped rotor, could be sticky caliper, could be wheel bearing. It will require disassembly and inspection to see what's wrong. Sticky caliper can be rebuilt usually, unless there is something dramatically wrong. When I got my low mileage car, the first task was replacement of all rotors, new pads, inspection of calipers and new fluid. Porsches have great brakes, if maintained. I wanted a clean slate and a solid baseline to start from.

Jim bailey - 928 International

My very first outing on a race track...Riverside my very first session The brake pedal went all the way to the floor !! My Instructor that day ? A guy I just met that day , Mark Anderson who very kindly took me out in HIS CAR ....yes a 928 ... that was in 1988. Mike made a very good comment about braking hard and for as little time as possible to limit heat transfer from the red hot rotor. Just as driving down a long steep grade holding the brakes on will soon over heat the brakes. You also do not want to stop the car and hold the brakes on as you leave the track and pit for the same reason heat transfer and the potential to warp a rotor since it cools unevenly when the pads are clamped to it.

mark kibort

i have 20 year old rubber lines and they work fine. i have more brakes than a 911 cup car, and its ALL stock S4 stock!

superblue and pagid orange is all you need. (and dont drag your brakes at the track.)

mk

mark kibort

also consider the "bedding" process. sometimes even "old" pads wont be bedded properly. this means you need to "cook" the "juices" out of the pad before they will be effective in track conditions.
also, there is really no place for a stock street pad on the track. they cook very easily and will boil the fuild. with a skilled foot, you can get away with it, but if you are new to the game, its going to be an issue.
i would be a little concerned with the disparate temps from rotor to rotor. generally, after a race session, my front rotors are 375f and the rears are 275f.

mk

atb

Charley,
I had serious fade issues on my '88 A/T w/stock calipers at one of the tracks out here (SRP) which is really hard on the brakes. I cured it by going with big reds all the way around, after trying numerous pad combinations and always using fresh fluid and stiill fading. No issues now.

I think a lot of it has to do with the driving technique used to get an A/T around the track. The 5 speeds weren't having the same fade issues. Were you braking differently in your S4 as compared to your 944?

cooleyjb

Happened to me at the end of a roughly 1 mile long straight in a 78 928. The brakes were getting spongy and it was taking one pump to really get the pedal to feel decent. Pedal worked for a bit and then went to the floor. Thankfully there was a nice runout area.

Came slowly back into the pits where teh pit marshall's eyes were wide open and he was jumping up and down. At which point the flames started to show over the freshly painted fenders. The street pads had caught on fire. Drove through a puddle and they stopped burning. Then I had the pleasure of telling my father (I was 17 at the time) that his car was done for the weekend halfway through the first session. I had been following him on track just prior to this happening. I wonder if there is a picture of the pads hanging around anywhere, I'll check on it.

After that a major brake upgrade to the 928 happened with good track pads and no issues since.

I don't think I've used street pads on track since.

mark kibort

I raced a 1979 928 at Thunderhill, bone stock, except the cat replaced with a high flow cat to a 2:10 on the long track. have you ever seen those hockey puck pads????? thunderhill is pretty tough on pads and is a very fast track. (not like road america, but faster than laguna) all i did was change the fluid and use a decent racing pad (mintex)

the point is, its all about the pad material, fluid and driver technique . you dont need big reds, as they can fade just as easily. remember the Evo in its first race a few years ago. they were complaining of fade, pedal, etc , because of their weight and " huge" HP. well, they weighed the same as me and guess what, their brembos were the identical ones on my S4. yet, for some reason, for 60 race days, ive never had an issue , not even a little one!! (and they are 20 years old too!!)

MK



mk

anonymousagain

...is this an appropriate summary (for the less versed with track brakes):

1) Synthetic brake fluid, period (ATE Blue, AP51,Valvoline SynPower, Castrol SRF, Motul RBF600)
2) <6mo fluid life and/or clean bleed prior to track day
3) Pagid Orange pads
4) OE brake lines (stainless not neccessary)
5) make sure pads are bed-in prior to track day

And a question - for street drivers, is there a pad that works as an adequate compromise? Perhaps the Pagid Orange are it?
Pad life is less important than best performance, but something that won't eat rotors or make too much dust for street driving... trying to balance as best as possible, 'cause Charlie's case seems realistic for most.

Excellent thread from all the experts !!!

Richard S

I was with Charley at Thunderhill last Monday. I didn't experience any brake problems. I used Valvoline SynPower fluid, about 6 mos old. New front rotors, somewhat broken in with the old pads, and I installed new Textar pad at the track. Several hard stops on the pads before getting on the track, and everything went just fine the whole day.

Dennis took my car out in the advanced group for a session, perhaps he can chime in on how my brakes felt to him. To me, the worked just fine. I echo everyones advice on new fluid. Cheap and easy to do.

Rich

Charley B

Rich - I think it was that lug nut you lent me. It did go on the right front which is where the temp. problem evolved. :>}