GT3 MKII Brakes on C2
03-10-2012, 01:54 PM
#1
Three Wheelin'
Thread Starter
GT3 MKII Brakes on C2
I just upgraded the brakes on my 99 C2 so I thought I'd share my experiences with this mod for anyone else that is contemplating doing it.
I considered the approach of using GT3 wheel carriers but I couldn't find used ones and the cost of new ones plus bearings & hubs etc was not economically feasible (I also did not want to upset the recent 12 hours worth of alignment/suspension & corner balancing work that had been done on my suspension).
So I went with the Rudtner racing adapter kit as per this link https://rennlist.com/forums/996-foru...t-3-stuff.html. It includes a modified (new) 6 piston caliper and an adapter that enables the new caliper to mount to the standard C2 wheel carrier using a stud-like arrangement.
To keep my braking system balanced I relocated my stock front calipers to the rear and installed a 4mm spacer between the caliper and the wheel carrier. This necessitates the use of red GT3 caliper bolts which are 5mm longer than Carrera bolts. OEM rear calipers are tapped for a screw to fix the brake line supporting bracket to the caliper. By moving the front caliper to the rear, I found there was no way to attach that bracket as the C2 front calipers are not tapped for such a screw. So I eliminated the small rear hard pipe and connected the flexible line straight to the caliper using a M10x1 convex male-male union. Note also that whilst the pad size is the same for a C2 front/GT3 rear setup, by using the C2 front caliper, the piston sizes are larger (40/36) than the GT3 rear caliper (30/28). Also worth noting is that the C2 includes a rear bias valve (which I have not touched) to reduce rear braking effect but the GT3 does not.
The front 6 pot caliper required a new hard-line to connect between the caliper and the standard c2 brake line supporting bracket. The part number is 996-355-581--9B & 9A.
So the parts I had to buy to do this mod included:
Rudtner racing Modified Porsche caliper & custom mount kit
350x34mm 996 MkII GT3 front brake discs.
PFC 08 Brake pads Front
330x28mm 996 MkII GT3 rear brake discs.
PFC 06 pads in 996 C2 front sizing = GT3 rear sizing. 0776.06.17.44
M12 4mm spacers x 4 generic
77mm GT3 caliper bolts x 4 999-067-042-09
Pin/spring kit for 6 pot caliper 996-351-959-30
Front caliper hardlines (L&R) 996-355-581--9B & 9A.
Male-male m10x1 convex unions x 2
Fresh brake fluid.
I retained the 996 C2 brake booster and master cylinder (initially). The C2 & turbo use a brake booster with a boost ratio of 3.85 whereas the GT3 uses a lower boost ratio of 3.15. The C2 uses a master cylinder with an 18mm stroke and 23.8mm piston. The Turbo & GT3 use a master cylinder with a 25.4mm piston & 18mm stroke.
Having now used this setup at the track I can say that the 6 pot brakes do work with the standard servo & master cylinder but I found it was too easy to over brake / difficult to be consistent with the brake modulation. For those reasons I plan to switch to the GT3 booster & master cylinder. My ABS is the standard 99 C2 ABS for cars with TC/LSD. My LSD is also upgraded to 40/60 which helps with braking from speed.
Aside from the difficulty with applying consistent brake modulation, the system felt great on the car. Definitely confidence inspiring and a lot more like the fantastic stopping power I used to experience with big brakes on my 951. From my own standpoint I am very glad that I went ahead with this change and it's put more fun into driving the car on track.
I considered the approach of using GT3 wheel carriers but I couldn't find used ones and the cost of new ones plus bearings & hubs etc was not economically feasible (I also did not want to upset the recent 12 hours worth of alignment/suspension & corner balancing work that had been done on my suspension).
So I went with the Rudtner racing adapter kit as per this link https://rennlist.com/forums/996-foru...t-3-stuff.html. It includes a modified (new) 6 piston caliper and an adapter that enables the new caliper to mount to the standard C2 wheel carrier using a stud-like arrangement.
To keep my braking system balanced I relocated my stock front calipers to the rear and installed a 4mm spacer between the caliper and the wheel carrier. This necessitates the use of red GT3 caliper bolts which are 5mm longer than Carrera bolts. OEM rear calipers are tapped for a screw to fix the brake line supporting bracket to the caliper. By moving the front caliper to the rear, I found there was no way to attach that bracket as the C2 front calipers are not tapped for such a screw. So I eliminated the small rear hard pipe and connected the flexible line straight to the caliper using a M10x1 convex male-male union. Note also that whilst the pad size is the same for a C2 front/GT3 rear setup, by using the C2 front caliper, the piston sizes are larger (40/36) than the GT3 rear caliper (30/28). Also worth noting is that the C2 includes a rear bias valve (which I have not touched) to reduce rear braking effect but the GT3 does not.
The front 6 pot caliper required a new hard-line to connect between the caliper and the standard c2 brake line supporting bracket. The part number is 996-355-581--9B & 9A.
So the parts I had to buy to do this mod included:
Rudtner racing Modified Porsche caliper & custom mount kit
350x34mm 996 MkII GT3 front brake discs.
PFC 08 Brake pads Front
330x28mm 996 MkII GT3 rear brake discs.
PFC 06 pads in 996 C2 front sizing = GT3 rear sizing. 0776.06.17.44
M12 4mm spacers x 4 generic
77mm GT3 caliper bolts x 4 999-067-042-09
Pin/spring kit for 6 pot caliper 996-351-959-30
Front caliper hardlines (L&R) 996-355-581--9B & 9A.
Male-male m10x1 convex unions x 2
Fresh brake fluid.
I retained the 996 C2 brake booster and master cylinder (initially). The C2 & turbo use a brake booster with a boost ratio of 3.85 whereas the GT3 uses a lower boost ratio of 3.15. The C2 uses a master cylinder with an 18mm stroke and 23.8mm piston. The Turbo & GT3 use a master cylinder with a 25.4mm piston & 18mm stroke.
Having now used this setup at the track I can say that the 6 pot brakes do work with the standard servo & master cylinder but I found it was too easy to over brake / difficult to be consistent with the brake modulation. For those reasons I plan to switch to the GT3 booster & master cylinder. My ABS is the standard 99 C2 ABS for cars with TC/LSD. My LSD is also upgraded to 40/60 which helps with braking from speed.
Aside from the difficulty with applying consistent brake modulation, the system felt great on the car. Definitely confidence inspiring and a lot more like the fantastic stopping power I used to experience with big brakes on my 951. From my own standpoint I am very glad that I went ahead with this change and it's put more fun into driving the car on track.
12-06-2016, 06:53 AM
#3
Rennlist Member
I'm curious if anyone else has tried this or how it is working out for the OP. Especially the part about using the front C2 calipers on the rear.
