The disc brake is a device for slowing or stopping the rotation of a wheel. A brake disc is connected to the wheel and/or the axle. To stop the wheel, friction material in the form of brake pads (mounted on a device called a brake caliper) is forced mechanically, hydraulically, pneumatically or electromagnetically against both sides of the disc. Friction causes the disc and attached wheel to slow or stop. Some newer mopeds come equipped with disc brakes, and older mopeds can be modified to use disc brakes.
See also: Drum brake