Rotor (Disc)

The rotor is a parallel-faced circular plate which is clamped by the pads in order to slow the vehicle. The rotor often has a series of vents which allow it to be cooled by outside air. The surfaces of the rotor are "turned" (machined) when the brake pads are replaced, in order to remove the "glazed" surface which forms with extended use. The turning process also "trues" the disc, which eliminates the pulsations experienced when the rotor is warped. Warped rotors give a slight tugging when the brakes are applied. If the rotor has been turned several times, it may become too thin to resurface, and require replacement. Semi metallic pads give good performance, longer replacement intervals and reduced "fade", but they also wear down the rotor more quickly than organic (non-metallic) pads.