Disc Brakes and Brake Discs

On a disc brake, a steel disc (rotor) is bolted to the wheel hub. When you pull the lever, hydraulic pressure pushes pistons in the caliper, which squeeze friction pads against both sides of the disc. Friction turns speed into heat. Nearly all modern motorcycles, scooters and ATVs use disc brakes at least at the front.

Discs can be fixed or floating (the braking ring mounted on carriers so it can expand freely), and drilled or wave-shaped to save weight and shed heat and dirt.

• Discs wear: measure thickness against the minimum stamped on the disc.
• A pulsing lever usually means uneven disc thickness or deposits, often described as a warped disc.
• Change pads before the friction material gets down to about 1–2 mm, or at the wear indicator groove.
• Keep oil, chain lube and polish away from discs and pads.