A rim brake is the type of bicycle brake whose pads press directly against the wheel rim. The friction between the pads and the rotating rim converts the bicycle’s motion into heat, slowing the wheel and the bicycle.
Rim brakes are usually operated by a handlebar lever connected through a cable or hydraulic system. Common designs include caliper brakes, cantilever brakes, V-brakes, and older rod-actuated brakes. Although their shapes differ, all apply braking force at the rim rather than at the hub or a separate rotor.
This distinguishes them from disc brakes, whose pads clamp a rotor attached to the hub. Drum brakes enclose their braking mechanism inside a hub, while a coaster brake is activated by back-pedaling. Rim brakes are light, inexpensive, mechanically simple, and easy to service, which explains their long popularity on road and commuter bicycles.
Their main weakness is reduced performance when the rim is wet or muddy. The pads and rim also wear over time, and a badly misaligned or damaged rim can make braking uneven.