The invention relates to a brake cylinder (100) and a hydraulic rim brake comprising a unit for receiving a brake pad (103). With known brake cylinders, it is difficult to remove the running wheel if the tire mounted on the wheel rim (6) is substantially wider than the wheel rim (6), since the wheel has to be moved through the gap between the two brake pads arranged on the brake cylinder. The brake cylinder according to the invention should have a simple structure and permit easy removal of the running wheel. The brake cylinder (100) according to the invention has a connecting member (302) for the arrangement of the brake cylinder (100) on a frame part (2″) in a manner rotatable about an axis, the axis being essentially orthogonal to the receiving unit for the brake pad (103).