nk993

Does anyone know what the piston sizes on the Brembo GT calipers are for the 993, especially for the rear?

The reason I am asking is because a distributor here quoted me 30/28mm pistons for the rear caliper... which is very strange to me as that means the rear brake torque, even with the 345mm discs is even lower than stock base brakes? The stock is 34/30 with 299mm discs. RS is 36/30 with 322mm. So the Brembo GT kit would have ~17% less rear brake torque than RS if my math is correct @Bill Verburg

Meanwhile they said the front 36/30/28mm which makes slightly more sense...but not when combined with that rear caliper.

They also said the GT, GT-S, and GT-R all use the exact same piston sizes.

nk993

I’ve gone ahead and confirmed this with BBI and race technologies. The rear pistons are 30/28…

this is a downgrade over even the base 993, let alone the RS rear. I fail to understand how for years they’ve been selling a $4k downgrade brake kit…

the worst part is the stubbornness where they tell you their engineers have expertly picked the correct piston sizes to match to the master cylinders bla bla bla when it’s clearly completely bull****

Peteinjp

The 964 rear Brembo GT is 28/30- it’s probably same caliper. The stock rear size on the 964 is 28/30.

The front 332mm 4 piston Brembo is also the same as 964 stock sizes 36/40 making this particular pair an excellent match for the stock 964 master…. not so for the 993 apparently.

Bill Verburg

Brembo Gt for 964 uses 36/40 front and 28/30 calipers on322x32 & 328x28 rotors, the improvement in brake torque & thermal capacity comes from the larger rotors, that's all good
this kit also reduces 964 front bias from 964RS 1/713 or 964 4/4 1.692 to 1.685, still not as good as 963 4/2 1.472 or 993RS 1.426 or 993 1.604

even a stock 96 can benefit from using a 23.8mm 993 m/c instead of the stock 20.6mm the 964 C4s uses 23.8 stock the larger m/c gives a harder higher pedal which is easier to modulate

pedal ratio
964 4/2 45.370 close to as high as usable and awful for modulation
964 4/4 43.004 slightly better

993 37.342 better yet
993RS 33.654 near ideal but still useable for those w/ less robust legs
964RS 32.786 again near ideal

Brembo GT for 963 43.004 w/ stock 20.6mm m/c again not so desirable from a performance perspective

32.342 w/ a 993 23.8mm m/c again near ideal

just for comparison 993 GT2 evo stand '97 27.826 great for younger pros

I believe that there is or was a different Brembo GT kit which Spyrex uses

28.30, 36 front 28/30 rear on 355x32 & 328x28 rotors bias is a poorer 1.857, pedal ratio w/ a 23.8mm m/c is 32.936

Brembo may also sell 350x28 rears w/ 32/34 calipers which would probably move bias too far back, I haven't run the numbers on that one yet.

nk993

I have had no luck with any of the UK dealers/distributors in convincing them to sell me a different caliper. All the Brembo M6 and M4 calipers are the same external shape I think, so i figured they can just swap the caliper with one from one of their other kits with slightly larger pistons, and the 993 brackets would still work fine. they refused to entertain that option and insisted Brembo are geniuses and that they're sure whatever brembo decided the piston size should be then they're correct. it feels like a cult

Bill Verburg

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