deputydog95

When I did the conversion on my 996 C2, we did the GT3 caliper, rotors, uprights, and the GT3 master cylinder. Pressed in new wheel bearings. Everything fit like a champ. No problems.

I would be surprised if your current MC will have the ooomph to handle the much larger front calipers. Guess you could try it with stock MC and see how it works.

Or.... take all the money you're spending to do this conversion and buy a stack of rotors instead

Odd that you're having these issues. Nick and Steve tracked the hell out of their C2s and did not run into the same problem you're having.

utkinpol

it may work. still i suspect you are dealing here with some GTS specific crap related to a lack of air flow in the wheel arch as they have changed something in the bumper or liners, or who knows what.

so what you also can try to do here, for a $0 cost - at next event take out your fog lights, then look at your liner in the wheel arch, at the spot next to where GT2 air duct begins on the inside, cut a 2"x1" rectangular hole so airflow from bumper would be directed close enough to gt2 duct, it may add enough air flow to reduce heat accumulation on the caliper. it is easy enough to put fog lights back on, or you can get permanent spacers for $300 or so.
it would also help to use some thermo paint to measure your factual heat level on the caliper before and after this change. bigger caliper with 6 pistons and bigger pads on a bigger rotors not necessarily will result in less heat produced during extreme braking, if your problem`s origin is in insufficient air flow it is may not be much of a help.

what BGB thinks of this issue? did you ask them about that? what is their opinion on rotors life expectation at sebring?

mdrums

I do need to get some of those thermo paint strips you tape on the caliper. The inside of the rotor doesn't crack as easy but the out rotor surface is all cracked up. Inside of caliper is brighter red than outside of caliper.
BGB says this is typical of these brakes on a car driven hard at the track.

mdrums

I've looked for GT3 uprights used...nothing out there that I could find on various forums for sale. I'm worried about the MC and brake bias with 6 piston 380mm up front and 4 piston 330mm in the rear but Bob said it would work. However I will now never know because I'm not going to go through the mickey mouse stuff to make that work and he is going to see if 997 Turbo 6 piston and 350mm rotors are direct bolt on.

utkinpol

well, it is typical, but question is - to what degree.

from engineering perspective alone i would say - try to measure max temperature on the inside and outside of you rotors and calipers.

if your cracks are related to extreme overall overheat it is one thing, if they are related to the extreme temperature fluctuation or a difference of a temperature drop speed on the inside and the outside side of your rotors - it is an another thing, both issues may require alteration of the existing air flow but in the different way. not enough air is bad, too much air directed to one side only is also bad.

simplest realistic path to remedy this crap is to drop off your front bumper, get a grandam or a cup car one and put in all proper ductwork and liners. i am not sure if it will work for you as you obviously like to drive your car on a street and with cup car bumper it is close to impossible. on my car now i have rottec front splitter that sits high enough for street driving, altered liners and custom placed ducts, permanently bolted to other plastic pieces to direct air better and my stock small oem rotors do not crack at all now, but it took some time to get it done right.

again, there are no univeral solutions here. if you will alter size of your rotors and calipers as well it may alter the air flow and remedy the issue as well, so, if 996/turbo calipers/rotors combo will fit and you will be able to get slotted rotors - try that path first as to deal with aero changes is tricky.

Nick Wong

If I read your problem correctly, you have a bias problem first and foremost, if the fronts are getting blown out and the rears are fat and happy.

You can try swapping out the MC for a more rearward biased one. That would take some of the energy dissipation out of the front system and make the rears work more, but that would be a bit of a handful in the rain if not done right. Food for thought.

utkinpol

hmm. what it is you mean by that? a manual dual MC combo from a cup car?
and how it is supposed to be paired with stock ABS in the GTS car?

any stock MC porsche has to offer, 'S' or base or GT3 one only differs by an internal bore diameter, there are no embedded adjustments for brake bias. that bias (how i understand) is done by internal valves in the ABS unit to which you connect feeding lines from MC unit. or do i understand it wrong?

Nick Wong

No idea. I am Porsche illiterate, and only offered that up as a suggestion to the problem at hand. On the Skyline GT-R we have tested four or five different OE MCs to get the right bias- ended up with a station wagon MC (Nissan Stagea 17/16") that has a few more % rear bias and firmer pedal for threshold feel. Good for dry tracks, a bit tricky for wet expecially if you don't have the right spring rates. By moving the bias rearward we were able to take heat out of the fronts. I think the new GT-R is even more rearward but they have the transmission/rear LSD in the back. ABS is four channel input, linked to ETS computer, and rear ABS is one channel output combined.

deputydog95

I don't recall Mike having this issue in his red 997S. And he was faster in that car

Izzone

Me neither......why mess with it, does the car not stop?

El Matador

Steve was Mr. Rogers in his c2s days, not the bad *** of south tampa he is now. Doesn't count.

mdrums

Car stops..I need to brake earlier than you guys for sure but my main reason for larger brakes is heat dissipation and to make rotors and pads last longer...bigger rotors and pads don't work as hard as small rotors and pads.

mdrums

Actually not really...my issues is I did nothing to the C2S just drove it and got use to it. I've been futzing around with different wheel sizes, tires sizes and brands, sway bars and now new coil overs and am not getting totally comfortable to the car. I haven't been studying my Race-Keeper data like I should either.

At Chin I instruct on Saturday and that has me occupied a lot and less track time the way green and red are. Bit on Sunday I'm just driving and should be in a better grove....so we will see.

I'm always trying to improve but not focused on ultimate hot flyer lap. I'm working on smooth consistent lap times over and over.

mdrums

I got the Porsche 6 piston calipers to fit by using Turbo 350mm rotors. The Turbo rotors are 20mm bigger than my stock rotors and the turbo rotor offset is correct for my upright. John from BGB Motorsports clued me in on all this. So I don't even have to use a spacer. The swept area from the 350 to 380mm rotor is the same some the pfc08 pads I bought from Clarke at Apex Performance fit perfectly.

Next step will be to upgrade my rear rotors and pads to 350mm ad this I will have the same brake system BGb and Rum Bum are running n in the Rolex Grand AM Continental series.

Alan C.

Mike,

So you ended up with 997tt rotors and calipers?

Hopefully this solves your issues. I used to go through a lot of pads on my RSA. I switched out to Big Reds and the new calipers paid for themselves in reduced pad usage.