A system is disclosed including valves which are opened or closed dependent upon the position of master cylinder pistons. Upon commencement of slip control, pumps supply fluid either into the slip control cycle or into the working chambers depending upon the position of the pistons. As a result, the pistons are reset until a pin of the valve reaches a ramp or cam and the valve opens. When the valve is open at the start of the control, the pumps first supply fluid into the open cycle, and the pressure fluid discharged from the wheel brakes for slip control is replenished out of the pressure chambers until the pin contacts the ramp or cam whereby pressure fluid supply from the pumps takes place.