Shakey brakey!

[Lemming]

Originally Posted by Racer Boy

Now no fade as far as a I can tell, because the rotors warp so badly that you can't brake hard after a few laps.

See -Warped- Brake Disc and Other Myths

[Nine8Six]

A cracked rotor will vibrate under thermal stress. Also true for improperly mixed cast iron (impurities).

A warped rotor will vibrate no matter hot or cold. Permanent stage.

Go easy on them until you find the cause