Description:

Brake disc (or rotor) is the rotating part of a wheel's disc brake assembly, against which the brake pads are applied.

The material is typically gray iron(G3000, HT250), a form of cast iron. The design of the discs varies somewhat. Some are simply solid, but others are hollowed out with fins or vanes joining together the disc's two contact surfaces (usually included as part of a casting process). The weight and power of the vehicle determines the need for ventilated discs. The "ventilated" disc design helps to dissipate the generated heat and is commonly used on the more-heavily loaded front discs.

Two piece discs (rotors) are a disc where the center mounting part of the disc is manufactured separately from the outer friction ring. The central section used for fitment is often referred to as the bell or hat and is commonly manufactured from an alloy such as a 7075 alloy and hard anodised for a lasting finish. The outer disc ring or rotor usually is manufactured from grey iron but in special applications can be from steel. Two piece discs can be supplied as a fixed assembly with regular nuts, bolts and washers. Key advantages of a two piece disc are a saving in critical un-sprung weight and the dissipation of heat from the disc surface through the alloy bell (hat).