Asco

Seems like something strange is going on in the rear..

ajw45

Yeah, I'm going to go back and see if I can get them to do the measurement with the rotors off the car. Seems like some folks have gotten funky readings in the rear maybe due to interference from the backing plates.

NMM991

That's not a bad idea, my rotors are off the car now that I have replaced them with cast iron.

I found it strange the my left rear rotor was the worse, and considering worse than the right rear; especially since my home track in Lime Rock -- 6 out of 7 are right hand turns.

Tried to make that argument with PCNA and got stonewalled.

CRex

Brake bias.

Happened to all my street GT3s.

gp1

I have a RS with PCCB coming. I plan to track the car and also worried about the really high replacement cost. I see a lot of you guys are shelving the stock PCCB and putting it back when at resale.

I did essentially paid for the PCCB as it was part of the total overall price ot he car. Not using is it like paying for something, not use it, and saving it for the next guy.

My thought was to simply run down the stock PCCB and when the time came use aftermarket iron options. Would resale be that negative if the car originally specced with PCCB but for sale with aftermarket option?

MaxLTV

Good point. It would not apply on the track as much because ABS would override any brake bias setting and make sure each wheel is at threshold, shifting most effort to the front. But at below threshold level, rear brake bias can make rears wear faster.

NMM991

My 2015 GT3 PCCBs wore fairly evenly front to back, 18,000 miles with 3,500 track miles. My 2016 GT3RS was very different - in general wear was much faster hitting the 18,000 miles wear levels in only 10,000 miles (1,100 track miles) AND one rear rotor was at 40% remaining life.

unclejosh

Guys

I have a set of Surface Transforms Rotors for sale that are take offs from my GT3 991.1.

The kit is from the UK, and the rotors can be refurbished 4x.

I sold my GT3 991.1.

I am kicking down a good deal to move the kit.

PM me for details.

isv

Even the 996s? The 7s I agree as stock wear the rears a heck of a lot but I didn't think it was also the case with the 6 (much stronger diff that doesn't have the rear brakes interfering like the 7).

ajw45

Update! Cliffs: Have rotors measured OFF the car

Went back to the same dealer and asked them to remove the rear rotors and measure them again. The service manager asked me 3 times if I was really sure I wanted to do it and even called the lead tech since they all thought it was a waste of time and I might be a little off in the head. However, after assuring them that if the numbers came back exactly the same I wouldn't freak out and that I would pay the tab either way the took the car....

New numbers!

Rotor---Max----On Car----Off Car----Min---New % Worn
LR-------55-----47.7-------52.5-------42----19.2
LR-------56-----49.0-------53.9-------43----16.2
LR-------53-----45.4-------50.4-------41----20

RR-------57-----49.4-------53.9-------43----22.1
RR-------54-----46.7-------51.0-------41----23.1
RR-------58-----50.6-------54.8-------44----22.9

The good news is there is a massive difference with the rotors off the car and the new readings came out to about 21% worn, less than half as bad as the original reading. If anyone is getting their PCCBs measured, definitely have them pulled off the car and thank you to everyone that suggested it.

I'm not upset that they didn't do this the first time since they didn't actually charge me for the first measurements and they are just looking to make sure the rotors are in spec vs trying to geek out and measure wear rates. However, I do wonder if owners have had to buy new PCCBs due to misreads. I would be PISSED if I spent $10k on PCCBs cause the tech didn't measure the rotors correctly and tossed a perfectly good set of rotors in the trash.

The rate of wear on the rears is still more than double that of the fronts even with the latest readings. That still concerns me but given the front rotors weren't measured off the car and the voodoo in measuring these things, who knows what the real rate is. I'll check again next year but if the wear rate is linear and I can go 20+ years just replacing a rear set of PCCBs that sounds like a good deal to me.

signes

^ Do you know how they measured them each time? My dealer uses the Carboteq tool by Proceq. Same technique on or off the car.

ajw45

Yup, same tool but the readings are different when the rotors are OFF the car. Something around interference from the metal backing plates so note the rotor is on a wood table in this video the tech sent to me...

https://qkvideo.net/#/service/watch/...be591248e6ec75

Ritesh

Good Info. Thx!!

CAlexio

Well this is the first time we’ve heard of anything like this. I can’t think of any information like this before. Is it possible that measurements have been done wrong for so long as they are almost always done on the car? Is it possible that these situations of PCCB wearing out prematurely are really just related to measuring the density incorrectly?

Petevb

From the Proceq documentation:
https://www.proceq.com/uploads/tx_pr...ngual_high.pdf

The GT3 has both an electrical parking brake and rear wheel steering actuators in close proximity to the rear rotors (perhaps very close depending on rotor angle). Both are motors that will be generating some magnetic field. I’m wondering if they are sufficient to throw the Proceq off.

Regardless of the reason the on vs off the car difference needs to be confirmed and raised up to PAG ASAP so they change procedure. If the difference is consistent this error may well already have cost Porsche customers north of seven figures while doing more damage to PCCB’s already fragile reputation.