Hydraulic rim brake

A hydraulically actuated rim brake (50) with a pair of brake arms (2, 3). Both brake arms (2, 3) may rotate about a common axis, which is the axis of a single bolt (1) that mounts the assembly (50) to a bicycle. The system has one piston slidably disposed in a piston cylinder. The piston's cylinder may be formed in one of the two brake arms (2, 3). Actuation of the piston in the cylinder causes movement of both brake arms (2, 3).