Abstract: A readily releasable parking brake for a bicycle includes a housing to be secured to the underside of the down tube of a bicycle frame, and a generally U-shaped spring wire form which has the ends of its leg portions received in a recess in the housing and turned out for pivotal mounting in a pair of aligned holes in the side walls of the housing providing for movement of the wire form through approximately 90.degree. between the back and bottom walls of the recess. Aligned grooves in the side walls of the housing adjacent their junctions with the back and bottom walls of the recess act as keepers for the legs of the wire form, and the head of the screw by which the housing is mounted on a bicycle is proportioned to spread the form legs into interfitting relation with these grooves, so that engagement and disengagement of the spring form with respect to these grooves is with a snap action.