pcar928fan

I put mine on backwards and my mechanic caught it later. I had not gone to the track or anything, but he noticed it. I didn't know which way the air was supposed to flow through them so I just got it wrong...

drnick

carbo pads from ring racing work really well.

Jim bailey - 928 International

Some have found that changing the brake proportioning valve shifts a bit more of the work to the rear brakes especially on light pedal initial braking. Also as mentioned using the brakes quick and hard limits the amount of time the pads are in contact with the rotor, the less time the less heat transfer to the pad and the less to the pistons and the less to the brake fluid. Often at the track , people will come into the pit and hold their foot on the brake pedal as they manuever into their parking place only to have the fluid boil over ! Too much contact for too long....

pcar928fan

I HIGHLY recommend going to the old Turbo brake bias bar (I think it is 45 bar or something like that) for the rear brakes on an S4 (taking them up from 18 bar). It really makes for MUCH better stopping power!

Jim M.

I agree, BUT the 18 bar brake bias valve was used only in the lawsuit crazy USA. The ROW cars had (IIRC) 33 bar valve. He could go to the 45 or 55 or 65 Bar valve though.

pcar928fan

Jim,

Thanks for the info! I was not aware that only the USA got the 18! I think I did the 45 bar on my S4. Works GREAT! I wonder if the 55 would be even better???

Jim M.

II ran with the 55 bar valve in both my 89 GT and also in the GTS. Works great!

RKD in OKC

On my 90 GT I was burning up the brakes, smoking pads, boiling fade, and warping rotors. Went to slotted cryo rotors and the 55 bar bias. Painted the rotors with some color changing heat sensitive paint. The paint color said the front rotors were getting up to 850°F before the bias change. The 55 bar bias valve got the temps down to about 700°F. I did have to pay attention coming up on a car on a clover leaf as the rear would just start to rotate as I applied the brakes. Not too bad though.

GregBBRD

Pagid race pads require serious break in proceedures, in order to work correctly. Ignoring these proceedures will usually result in a one way conversation with "God".

The difference between the source of "brake fade" between the pads and the fluid is very obvious. Pad "fade" is when the pedal doesn't change feeling, but the car will not stop, regardless of how much pressure you put into the brake pedal. There is no way to fix this, short of letting the brakes cool. This is actually what I think is being described, here.

Boiling fluid results in the brake pedal going to the floor, without any resistance. Rapid "pumping" and praying will usually result in a return of the brake pedal.

Bill Ball

Well, it all depends on which way you look at them. From the top view, they are curved backwards. Regardless, they face away from the direction of rotation. (Don't get confused by the slots cut in the surface)

brianrheffron

Overheating of the brake fluid seems to be at the root of brake problems on the track so anything to disrupt the disc to pad to brake fluid heat transfer path should be a good thing. To this end Race Tech sell thin titanium pads that fit between the pad and the brake piston. In the UK there is at least one company that will machine you a set of stainless steel brake pistons usually to prevent corrosion in the brakes of off roaders. Stainless steel is a much poorer conductor of heat than aluminium so should keep the fluid cooler. This could be one worthwhile mod.
Anything to make the disc run cooler will also help the situation. No matter how you duct air to the disc, as it rotates it will carry with it a very thin layer of air on its surface; the boundary layer. This actally insulates the disc raising temperature. If you can disrupt this layer and create turbulance close to the disc surface it will cool faster. In the good old days of British touring car racing
some teams used Ford Facons and Galaxies but their small disc brakes would fade after only a few laps. One team managed to limit this by bending some thin steel rod to conform very closely to the the shape of the disc and fixing it to the calliper. This disrupted the boundary layer, cooled the discs and gave them a few extra laps of good braking. This mod costs next to nothing and could be done in a couple of hours. Anyone care to try it and report back.

Jim M.

I also read somewhere that a coating of anti-seize on the back side of the wheel where it contacts the hub helps transfer the heat to the wheel and hence reduces the temperture of the rotor and caliper. May also be worth a try and cheaper than titanium plates.

brianrheffron

Wheels are connected to the hub not by shear in the studs but by clamping pressure/ friction between the back of the wheel and the face of the hub. Maybe using anti-sieze in this area is not a good idea.
If the face of the hub was cleaned to a bright finish removing all corrosion and the mating surface of the wheel was stripped and likewise cleaned that would give you a good heat path. Some portion of brake heat would be conducted to the wheel and lost that way. Every little helps.