I am upgrading from my 991S in which I do 10-12 HPDE events a year TO A 991 GT 3. The S has upgraded rotors and pads to minimize fade vs OEM. How do the stock GT3 brakes differ from the S?

 

I did the same thing, but my S had PCCBs. The standard S brakes are 340/330mm f/r. The GT3 standard brakes are 380/380 f/r.

I am not sure where you DE but I had no fade from the PCCBs on the C2S at Sebring. I have not tried the GT3 there yet. I suspect higher speeds will put a bigger burden on the GT3 brakes. Based on how well they hold up I may upgrade the pads.

 

The Standard 991 GT3 brakes are 380 x 34 front (6 piston), 380 x 30 rear (4 piston). The limit of the brakes is often the tire and car setup. The better the tire, the more the stress on the brakes.

The S PCCB brakes are 350 x 34 front, 350 x 28 rear so significantly smaller. This means less brake torque and heat mass.

From our experience, 991 GT3 does best with upgraded front rotors (like a Brembo Racing setup) and endurance pads. Rear: Stock rotors with endurance pads. This is what we are using with our customers anyway.