The invention relates to a combined vehicle brake, comprising a hydraulically operable working brake and an electromechanically operable parking brake. The parking brake acts on a brake piston (5) by means of a gear (1). The gear comprises a threaded spindle (2) and a threaded nut (3) which contact each other by means of several roller bodies (4). The invention further relates to a gear for converting a rotational movement by means of a threaded spindle and a threaded nut which contact each other by means of several roller bodies. According to the invention, a high working efficiency with reduced electrical power consumption can be achieved by arranging the roller bodies (4) such as to be able to move between two stops (21, 22) in the thread path with a first spring element (10) arranged between the roller bodies (4) and a stop (21) and on load-free operation of the gear (1) slippage of the roller bodies (4) is permitted and, on operation of the gear (1) under load, rolling of the roller bodies (4) is permitted.