goldfishhh

Too much track time... mmmk.

Steveo369

Those appear to be 1-piece rotors.

When the brakes are applied, the outer portion of the rotor heats up more than the inner hub, effectively stretching the outer portion of the rotor. The outer hole created a stress concentration and "pop", the rotor cracked.

This is one big reason to go to a 2-piece floating rotor, so that the rotor ring can expand more evenly without being restrained by the inner hub.

I'll venture a guess and say that x-drilling isn't as apt to cause this kind of problem on 2-piece rotors.

jprice@CPS

Sorry, but not true. They crack as well.. seen it in person on two cars.

J4SON

Not true, I've cracked 993turbo rotors myself

jprice@CPS

The problem is holes in the rotor, not too much track time.

goldfishhh

Cross drilling is teh suck and causes this to happen even more.

It happened to my slotted rotors because I wore them down under spec and repeatedly heated them up to glowing hot over and over.

jprice@CPS

Yep.. they eventually crack either way.. cross drilled quickest death ;-)