Don't drive with your nannies on!
With active handling in competition mode, yaw control is still active and using the rear brakes to correct slides/excessive yaw on corner entry and exit. This causes the rear brakes to run hot, and in my case one of the rotors cracked as it cooled down in the pit. I even heard the *PING* as it happened.
In hindsight, the nannies were keeping me safe (as they are supposed to). I drove one session with TC and AH disabled - and spun the car. Coming from a Lotus Elise I'm used to mashing the throttle on corner exit, there was never too much throttle with an 1.8 l mid-engined car.
305 to 330 mm brake rotor
After some research online, I found that the C6 with the Z51 option code uses a larger 330 mm brake rotor, but share the same caliper and parking brake dimensions.
- Increased thermal capacity. The EBC Z51 rotors are ventilated on both sides, have a higher mass and increase the swept diameter of the brake pad
- Better looks, the brakes fill the 18" wheel and looks more in balance with the front big brake kit.
- Reuse of stock brake calipers and parking brakes
- Change of brake brake bias. The increased rotor diameter causes a braking torque increase of ~ 10%, which could affect the front to rear brake bias. The C6 Z51 caliper has a smaller diameter brake piston to compensate, but I'm expecting the marginal brake torque increase to be within the capabilities of the ABS system, preventing early rear brake lockup.
- Increased unsprung mass, from 6.5 to 6.9 kg.