A hub mounted on-vehicle lathe is highly recommended. This type of lathe trues the rotor to the vehicles hub/bearing.The disc brake rotor can be machined if scored or worn. The on-vehicle lathe must machine both sides of the rotor simultaneously with dual cutter heads. The rotor mounting surface must be clean before placing on the on-vehicle lathe. Equipment capable of machining only one side at a time may produce a tapered rotor This type of rotor machining is not recommended.Proper wheel torque is also critical to help prevent any warping of the disc brake rotor.Brake rotors that do not meet minimum thickness specifications before or after machining must be replaced.