The brake disc is the friction coupling part of the disc brake. In addition to the strength and stiffness required as a component, it should also have a high and stable friction coefficient as much as possible, as well as appropriate wear resistance, heat resistance, heat dissipation and heat capacity. The brake disc (or rotor) is a rotating part of the wheel disc brake assembly, on which the brake pads rest. The material is usually gray cast iron, a kind of cast iron.