discbrake

A disc brake is a braking system that uses a brake rotor (disc) attached to a wheel and a caliper that squeezes friction pads against the rotor to slow or stop rotation. Braking force is generated by friction converting kinetic energy to heat, which is dissipated by the rotor and surrounding airflow.

Components include the rotor, caliper, brake pads, and a method of actuation—hydraulic fluid in most automotive and many bicycle systems, or a cable in mechanical bicycle disc brakes. Some systems use multiple pistons in the caliper for increased clamping force.

Rotors are typically made of cast iron and are either solid or ventilated (and sometimes cross-drilled or slotted for heat management). Calipers can be fixed or floating; fixed calipers use multiple pistons on both sides of the rotor, while floating calipers move laterally to apply pressure.

Materials for pads vary: organic, semi-metallic, and sintered compounds, chosen for grip, wear, and heat tolerance. In cars and motorcycles, discs are commonly paired with hydraulic actuation and anti-lock braking systems; in bicycles, hydraulic or cable-actuated disc brakes are common.

Advantages include strong and consistent braking with reduced fade under repeated use; better performance in wet or muddy conditions; and lower susceptibility to heat buildup in some configurations. Limitations include higher cost, more complex maintenance, rotor wear and occasionally warping; performance depends on pad condition, rotor condition, and proper bleeding and calibration in hydraulic systems.

History notes that disc brakes were developed in the early 20th century and became increasingly common in automobiles from the mid-20th century onward; bicycle disc brakes gained popularity in the late 20th century as an alternative to rim brakes.