build.bat

i swapped my PCCB rotors and pads for girodisc rotors and using cobalt xr pads. i am wondering if this could have any negative effect on the ABS. when on track with cup2s, dry track, i seem to be hitting ABS way earlier than i would expect. either the rotors+pads are way grippy and the tires just can't handle the braking, or maybe there is some mis-calibration in the ABS module? track is high plains raceway in denver, condition of the track is pretty good to excellent surface and none of the days i would say had abnormal conditions like had a WRL event the day before with tons of rubber left on the track, etc.

i was thinking of swapping back my PCCB for next track day and testing my theory or i can try a different set of iron pads, but like i said, it does not appear the braking grip seems to be the issue.

steveP911

I changed from PCCB to GiroDiscs and Ferodo DS3.12, then Pagid yellow pads. I have a 997.1 C2S. I don't recall having the ABS issue you are talking about except when I ask too much of the brakes in a high-speed slowdown. Not an expert but as long as your tire sizes match the OEM setup (front dia approx 1/2" less than rear) I don't see how your ABS is misbehaving. Did you change to Cup 2's at the same time? I'm not familiar with Cobalt pads (but a quick check shows 5 compounds - which do you have?). Did you check with GiroDisc or the rotor/pad seller(s) about the matchup you now have, along with your tire selection / car / driving level?

build.bat

yea, running OEM wheels and tire sizes on cup2s. i never ran the PCCBs on track, i basically drove it on the street until break-in service, then got track alignment and swapped the PCCBs and now its a track only car. so right now my only experience on track is this one setup with 992 gt3, which is why i am wondering what might be going on. these are the cobalt xr1s, which i ran in a g80 m3 on the same track many times without issue (though i had the OEM rotors on the BMW)

girodisc did say that they saw no issue with the cobalt pads, but i have a set of girodisc's equivalent pads (recommended by girodisc) ready to try as well. i guess swapping to the girodisc pads would be easier then swapping the PCCBs back, if i have to start trying a few things. i mainly wanted to at least see if others have had success with swapping rotors / pads from PCCB to iron without issue, seems like it, so maybe just swapping the pads should be my next test.

these cup2s have about 1/2 track day left, then i have a set of goodyear f1s to ready to try. i have tried cup2 Rs on g80 before and because most of my tracking is long 6+ hr days in higher temps, i found the cup2rs to be better for 1-2 sessions and then suck the rest of the day due to heat soak. so i decided to try the F1s, but never had issues like this with cup2s previously. still puzzled where the issue may be at: tires, pads, rotors, ABS system, etc

ParadiseGT3

Interpreting correctly that you didn't run on track with PCCB, so this is based upon first track day with the car (w/ girodisc setup)?

By what measure do the Cup 2's have 1/2 day left? They're probably dead, heat cycled, likeliest cause for overactive abs. Loss of braking performance is sure sign.

Probably not relevant for your situation, but do find the PCCB calibration different w/ Girodisc setups vs. factory iron calibration w/ Girodisc setups. Not in terms of abs, but pedal characteristics. All things being equal with the Girodisc setups -- fluid, pads, discs -- PCCB calibration doesn't have the same initial bite for me.

nineball

i changed my 718 S and my 987.2 S from iron to giro and there was a noticeable improvement in braking. no experience with pccb so can't comment on one vs the other but the giros are top notch gear.

build.bat

ok yea, let me just add a few more details, but also let me just say, i dont think i have enough information to properly solve this yet. i certainly believe and hope that this is an occam’s razor situation, the simplest theories is probably what is happening here. i just wanted to double check with others that have done this swap, PCCBs to iron for track, that there wasn’t some sort of computer / calibration issue, before i start chasing physical/mechanical issues.

4 track days on this setup, girodisc + cup2s (which had 900 mi of basic street driving for break-in period) and 2 of those track days for PCA days, so very minimal # of laps and not nearly at 100% on the PCA days. so by 1/2 a track day left, i was simply trying to say that i have multiple days on this setup and the experience has been the same each time as far as i can remember. something i did not experience before with m3 (g80) and m235iR on the same track, similar weather, etc. g80 on same pads and cup2s as well. both g80 and gt3 also had fresh motul 660 fluid.

this may also just be my inexperience with porsche and coming from BMW, i may just not be used to the brake dynamics of the vehicle, but it seemed strangely and aggressively hitting ABS. once i switch over to the new rubber, i will certainly do more pointed tests. it seems like tho, there shouldn’t be too much issue with this swap, or at least i should focus on more normal stuff, like tires (wear and temps) and try and see if its happening all the time or not.

thx

Matt Romanowski

Have you looked at https://rebrakeusa.com/ for maintence on the PCCB? I have no idea if they are really good, but their post on FB and customers response seems pretty good. I think if I had a PCCB car, I would consider just running the PCCB and having them redone when needed.

ParadiseGT3

Can say for sure that the PCCB to Girodisc transfer does not necessarily result in overactive, disruptive abs characteristics. If you experienced this from day 1 with the Cup 2, it might be technique.

Come from a decade + with M cars. The braking technique is certainly different with GT cars, and especially with the RS, keep in mind it wants you to get a big chunk of any high speed braking done on that initial hit with the aero in full effect.

Not saying you are, but if you dilly dally on the brakes, start modulating to correct initial misapplication, get the trail wrong, then entry imbalance can result in the abs and/or esc/tc aids starting to correct your physics.

ParadiseGT3

I'm about through the girodiscs that came on my RS, with the PCCB boxed up. Had the PCCB discs checked at the dealer, plenty of life left. So think I am actually going to run them and consider rebrake when the time comes. They're "free" and I also want to see what I make of that unsprung weight loss.

build.bat

they don’t list any prices. i wonder what it costs vs replacing the the girodisc rings. (~$2200 for all 4 replacement rings)

seems like the pagid rsc1 pads for pccb are about the same prices as any other steel track pads.

build.bat

yea when i swapped my rotors i weighed the PCCBs vs girodisc, 14 lbs for PCCB and 28 lbs for girodisc per rotor, so ~40 lbs of unsprung weight loss, but sadly for me, i am not probably not limited by that currently on the track, still very much a beginner, and make much more fundamental mistakes than worrying about PCCBs vs steel

build.bat

yea i am hoping it technique / application, that is easier to correct than any sort of mechanical / software stuff

ParadiseGT3

RS braking performance is pretty mind boggling coming from more normal performance car platforms like M.

Provided you have the tires for it, aero in maximum attack, proper alignment -- considerably deeper into a high speed brake zone, smooth but very aggressive initial application, then the trail is pretty accelerated as well. Overall less time under braking than you're used to. RS returns to equilibrium for turn in so quickly, efficiently. It doesn't respond well to any half hearted braking techniques Also allow the front axle to work on turn in similar to an M car.

Ximian

Not actual numbers but they've posted before that it's roughly half the price of new PCCB rotors. Shipping to Germany and back can't be cheap.

steveP911

Yes, it is a bit of a weight penalty to give up the PCCB rotors, but I just couldn't swallow the $$$ when needing new rotors. Also, I do not think I am at the driving point where unsprung weight is a critical factor - i.e., I am not good enough to appreciate. Not saying that should apply to you.

I did find that a very brief ramp-up in brake application did help plant the car (all four tires) and allow me to then go to max brake without much unsettling/ABS. I wish I could graph my guess at the ideal brake pressure curve. Pretty sure that any max brake application has the potential for triggering ABS. Maybe just experiment with this? Like you said, much cheaper than new parts.

Last thing. Are you regularly checking your alignment? Are both rear wheels equally set with proper toe-in (not out)? I discovered this once and it had played heck with me in max braking zones. Added a toe link locking kit to resolve it.

Good luck.