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Larger 330 mm rear brakes from C6 Z51

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. 

Plus

  • 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

Minus

  • 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.


Stock C5 rotor and bracket compared to C6 Z51 rotor and bracket. Notice that the EBC Z51 rotor is ventilated on both sides, which is not the case for the stock C5 or Z51 rotor. Another benefit is that the EBC rotor is blank, no drilled holes prone to cracking as in the OEM Z51 rotor.



New rotor and bracket installed, using stock caliper and parking brake shoes.

Parts list

1 x EBC D7417 Ultima brake rotors (left and right)
1 x EBC DP51160NDX brake pads (left and right)
2 x GM 88964167 C6 Z51 caliper bracket (same left and right)






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