Wilwood's new Dynamic Bobbin Mount Hats incorporate a new rotor mounting system that allows the rotors to move independently of the hats as they expand and contract through heat cycles. All thermally generated stress is removed from the rotor attachment points. The rotors stay flatter and run truer. Brake response and pedal feel remain consistent. Pad knock back and rotor drag are eliminated. The hats are no longer distorted by stresses generated by thermal expansion and shrinkage of the rotors. All problems associated with thermal distortion are eliminated.