Originally Posted by msheredy
Cross-drilled or slotted rotors are not meant to dissipate heat. Vented rotors are. Cross-drilled or slotted rotors allow the expanding gases that build between the pad and the rotor (when the brakes are applied) to escape. This makes the brakes work more efficiently. Plus they look really cool!
actually I believe the cross drilled rotors are not designed to remove gasses even though they do have that effect, but the real reason for drilling out the rotor is to remove excess rotational weight from the car's driveline. this is only necessary for full ***** to the wall race cars who are trying to shave off every ounce of weight.