997gt3north

- never occurred to me that the brake pads would only last 3 track days especially when the trackdays were my first in the car, the car especially for the fist day was maybe doing 6/10th and on the second day half the runs the track was covered with water and on the 3rd day I only did 3 sessions before driving home

- but, took a look at the pads today and the REARS are almost totally gone - fronts look like they are about 1/4 used or have 3/4s to go

- as soon as I saw this i am guessing that this likely explains the further pedal travel - it would just figure that Porsche has decided to make changing the rear pads a more difficult process (i.e. caliper must be removed) than a simple remove the bridge, pop out the old pads, put in the new pads 10 minute routine

- i also have to say, who the fvck at Porsche could have gotten the bias this wrong that you will likely need 3 sets or rears for every set of fronts??

- it is unfortunate that it would seem that the 265MPSCs don't easily fit inside the front wheel as this maybe enough to get more front bias (am I wrong in thinking this?)

- the rear rotors are getting airflow (there is a duct bringing in air) so this can't be the major issue so is it brake bias? - if so, is there any easy fit for this?

- again, I was not overly hard on the brakes as the conditions just weren't right for it so anyone have any thought?

Oh, and I called Porsche Motorsport in cali trying to get some help - don't expect any here as no Porsche Racecars in America run ceramics. What they did say was if I send a picture and a trace on the stock pads, they will let me know if they are a match for the 996 Motorsport Pads. On this point, I asked if the Motorsport Pads were developed to work with Ceramics - their answer was NO - but that they offered the pad as a Porsche Part# that some 996GT3 customers would order through the dealership and they would send them - the feedback on this point was some people loved them, others didn't, and some complained about aggressive ceramic rotor ware.

Anyone got any ideas, suggestions, etc. ?

thx

Paul

mooty

wow, three days for rear pads.. i suspect something is not right. the bias is way too rearward to have 3:1 ratio of rear vs front.

i am very unhappy of this new rear caliper design... removing the caliper to change pads. this is a** backward .

RR

Sorry for your troubles. But that's the reason I decided to go with steels on my RS.

frayed

I think carrera GT posted temperature of the rears that were excessive. Now you've confirmed it. This is ****ty, and a black mark on an otherwise outstanding car.

I hope the aftermarket comes to the rescue.

My bet its more an airflow issue than rear brake bias. I talked with one race team who stated they've had a lot of airflow problems on their 997 cars, due to porsche's obsession in lower CD.

BobbyC

I'm scratching my head here and can't for the life of me figure how your rear pads were gone after 3 days????

Alan Smithee

Were you hanging the tail out? Perhaps the traction control was working overtime?

stout

Remember that Porsche AG announced that the new GT3 adjusts braking bias rearward under heavy braking to take advantage of the wide, wide rear tires....


-I wonder if this is playing a role in the rear-pad wear you're experiencing. If so, it is surprising that this would not have been unearthed in Porsche's development period for the GT3.

Once computers get really involved, things can get interesting... but 3x seems excessive to me. Perhaps Adam and others can provide more pad wear data points? Track configuration could be playing a role here, too.


-I do not think worn pads would result in a loss of brake pedal pressure. At least, I've never seen it (unless you're talking about worn-pad-related fade). As for the scary experiences with 997 ABS/PCCB Gen II+ described in the other post, as well as the *exact* chain of events following at the owner's dealership, I now suspect a fairly recent experience I had was no fluke.

This subject should be ear-marked and observed. Maybe there is a problem here. Maybe not. Time will tell.

Be safe out there...

pete

eclou

This was with PCCB correct? Damn glad that the rotors are so tough that the pads just vaporize in fear.

BobbyC

Can u post some pics of the worn pads and also take a measurement of thr remaining thickness? Are the pads cracked? Do you see white ash around edges of the pads and/or white ash like streaks across the pad surface? This info would be helpful in discerning what's going on. Thanks...

Carrera GT

You removed all pads from both rear rotors?
What were the thicknesses at the center on average?
Remember, the ends are heavily camfered.
Did you find the correct torque to reinstall the rear calipers?

Don't go to an agressive pad in the rear -- you don't want rotor wear and if rear bias is an issue, you'll want less bight in the rears.

I find the rears run significantly hotter than the fronts and I would put more cooling back there.

I haven't found a factory part to increase air-flow to the rears.

I've played with TC and am quite confident it's not contributing to the rear brake temperature.

I haven't experienced excessive rear pad wear compared to front -- over a lot more track days -- they're both at about 50% at last examination.

For a soft pedal, I'd suspect fluid and boiling, not thin pads, but thin pads will let through more heat of course and contribute to exceeding boiling points. For pedal travel, sure, really thin pads in the front, but no so much in the rears, the pistons don't have that much volume and they will stay on those flat ceramic rotors without getting knocked back into the calipers. Also, if you still get pedal travel after a pump or two, it's spongey, not travel -- that's what I've heard reported from some PCCB drivers.

Yes, I agree the rear caliper design is a step backwards -- the first Porsche caliper I've encountered that's not a quick pad change design (except for the street cars designs etc.)

ps. If you want to see a beefy caliper, check out the fronts on the new Cayenne Turbo ... huge ... I was looking for the "Kenworth" brand ...

NJ-GT

Pete, I didn't know about the computer controlled rear brake bias. Pretty cool stuff.

I've a wild guess about the soft pedal issue. This is my guess:

The computer detects a heavy braking condition, so fluid pressure is increased to the two rear brake lines. As more bite is applied to the rear brakes under heavy braking, the brakes will get hot. Eventually, the rear rotors and calipers are very hot, the fluid for the rear lines gets hot and less effective. The driver then applies more brake pedal, the computer sends more pressure to the rear lines because this is an even harder braking condition, but the fluid is already boiling, so the driver keeps applying brake pedal.

This guess would be easy to identify. Attach plastic rings to the front and rear brake lines, look for a cheap plastic that melts at 500-600 degrees. If the rear rings melt while the front ones don't, there is your answer for a sponge brake pedal.

You can also check the temperature for the lines when the condition occurs, by using a pyrometer.

The problem is that whatever aftermarket set of rotors/calipers/pads is installed, the line pressure is still controlled by the stock ABS unit.

A fix could be to install a proportioning valve on the rear lines, so the flow pressure gets reduced.

Anyway, if my guess is correct, it's a design problem and it should be corrected by Porsche. I'm afraid about the longevity of the rear PCCB rotors if they're continuously exposed to excessive wear and heat.

frayed

Pete, you lost me there. What were the (i) scary experiences and (ii) exact chain of events at the dealership, and (iii) your recent experience? And, is brake bias dynamically controlled by the ECU?

iLLM3

Would love to know as well, wow i love this forum.. Its a never ending wealth of knowledge

tdf360

So what does a set of pads run on the PCCB-equipped GT3?

Gary

Carrera GT

From memory it starts with a "3" for a set of rear pads and it starts with a "5" for a set of front pads.