Can anyone help me with a question that rose up with my brake upgrade project. I'm installing GT2 calipers and discs to my 951 and planned to use GT2 iron ( M449, #996 351 409/410 9H ) discs.Now I'm about to get GT3 Super Cup car's discs ( 350x33mm, 996 351 409/410 9J ) with a very reasonable price,but there's one question that the seller/dealer can't answer. Is it a direct replacement to GT2's disc,ie is the distance from hat's inner surface to rotor's center the same?And is there a problem with bolt circle b/c the 9J is from a car with centerlock wheel...
Do you have knowledge or can you please measure this for me? ( The distance from hat's inner surface to rotor's inner surface is also OK ! )

 

996GT2, 996GT3 and the 6 piston front caliper 996 GT3 Cup use the same offset and diameter rotors.

I've 996 GT2 calipers at my four corners. The GT3Cup front rotors are a direct swap.

However, the GT2/GT3 equipped with PCCB use a different size rear rotor. If you're using GT2 rear rotors (the car came to U.S with PCCB standard), then you will need custom steel rotors for the rear, because the 996GT3Cup rear are smaller.

 

I believe these should be OK as NJ-GT said.

Did you update the master cylinder to match?

Also the brakes on the 911s are proportioned with respect to the rearward weight bias, you may need a brake bias valve to fine tune this.

 

Thanks!

I will use GT3 rear calipers and steel rotors,330x28mm.

I will start with std 951 master cylinder,it should be adequate,because:
951 pistons: F 44/36 mm,area 25,38 mm2,R 30/28 mm,area 13,22 cm2
GT3 pistons: F 44/36 mm, R 30/28 mm
GT2 pistons: F 38/32/28 mm,area 25,54 mm2, R 30/28 mm.

I have two different brake bias valves to play with for balance...

 

Why do the Cup cars use steel rotors instead of the composite?

 

grussell,

Search the forums for "ceramic" or "PCCB" and you will get an ocean of return hits on these topics!

Ciao,

Johannes E.

GT3 CS