Carrera Brake R&R

[North Coast Cab]

I've just returned from a 3 day track weekend and I'm doing some work on the stock Carrera brakes. Here's what I'm experiencing on brakes that are totally new within the last two years. I've done about 16 track days and 1500 street miles. New stock solid rotors, front brake cooling ducts, PF 97 pads, and rebuilt calipers.

Front pads 70%, rear pads 10%
Outer caliper piston seals fried and crunchy on all four calipers. Inner seals seem rubbery and plyable

Is this normal? How often will I have to rebuild the calipers? Why do the rears wear so fast? Anything I can do to extend the life of any of the components?

John

[Bill Verburg]

The Carrera has more rear bias than earlier cars, the p/v is supposed to compenstae but only does so at line pressures >33bar

To use less rear brake you need to push harder for a shorter period of time, but don't jab the brake as that creates pressure spikes that are worse.

The calipers saw temps of 400 - 1000&degF or so and will need to be replaced after each track event unless you can get the rotor temps down and keep them there at all times.

A Carrera is a very underbraked car for track use, if class rules allow 930 size or better rotors are the best way to reduce temps.

Cooling helps but only marginally in this case.

[OZCarrera3]

Originally posted by Bill Verburg
The calipers saw temps of 400 - 1000&degF or so and will need to be replaced after each track event unless you can get the rotor temps down and keep them there at all times.

Bill, I would assume any track work that resulted in noticeable brake fade would mean that rotors have seen in excess of 400 degF (and my understanding is that 400 is not that high for brakes)? Do I understand you correctly that your statement means that you need to rebuild the calipers after every track day?

I not doubting your expertise in general when it comes to brakes and their packaging and maybe I have misunderstood the intent of your comment, but I would query the fact that they need to be rebuilt after each track event. I've done two track days on my brakes that have not been rebuilt in the last 2 years at the very least (nor have I seen anything in the PO receipts that suggest that this has been done in the last 5yrs), where I have experienced very hot brakes to the point where they were fading excessively (i.e. 50% or more increase in pedal travel). To date there have appears to have no lasting issues, the brakes pull the car up fine with excellent pedal pressures and no leaks or funny noises. The only preparation I've done is to replace the brake fluid with AP Racing 551 fluid.

Could you please restate the intention of the above comment?

[North Coast Cab]

Bill,
Thanks for the input. I have never experienced fade so I assume they have never really gotten to the high end of the temperature range. I think I do a pretty good with my braking, but was wondering if these are normal attributes. I guess I'll rebuild the calipers, change pads and move on. Just wanted to make sure there were no other issues.

John

[Bill Verburg]

Originally posted by OZCarrera3
Bill, I would assume any track work that resulted in noticeable brake fade would mean that rotors have seen in excess of 400 degF (and my understanding is that 400 is not that high for brakes)? Do I understand you correctly that your statement means that you need to rebuild the calipers after every track day?

The calipers during use generally do not see temps of 400 F. The seals are toasted if they do. Seals are generally rated to 360 - 400 F max but begin to harden at much lower temps, it's a time @ temp relation. 1 hour @ 300 is equivalent to a few minutes at 380 and it's cumulative, but nonlinearly


a few minutes at 440&deg, will be ok the first time but not the tenth.

[JeremyD]

With todays higher boiling point brake fluid it's easy to fry your caliper seals without getting fade. ask me how I know. Especially in a fat a$$ cabriolet.

[Bill Verburg]

I have never experienced fade so I assume they have never really gotten to the high end of the temperature range.

Not necessarily true. The newer high temp track pads can easily handle temps to >1000&degF w/o fade. The weak link here is rubber parts, fluid and rotors.

[randywebb]

Typo: remove the 7 or a 0 from Bill's post above.
The Solar surface apparent radiative temperature is only 6,000 oF.... so I don't think the brake pads will withstand that temperature.

[Bill Verburg]

RW Thanks, i was in a hurry and didn't proof it. Corrected now

[randywebb]

no prob -- "keeping it real" if not "down to earth"

[North Coast Cab]

Ok so the seals go after X amount of high temp time. What about the rear pad wear, is that normal?

John

[OZCarrera3]

Sorry for the misunderstanding Bill, 400 degree caliper temps are obviously a whole lot different story to rotor temps - my bad.