Brake pressure control valves with fluid pressure responsive valve

A pressure control valve assembly for use in vehicle braking system having separate pressure circuits, comprising a fluid pressure responsive valve adapted to be inserted in one of said circuits for controlling the flow of pressure fluid therein, the valve having a valve closure member and a cooperating valve seat, spring means urging said valve to an open position, a pressure differential responsive member adapted to be subjected at opposed ends respectively to the pressures in said circuits and normally occupying a first position, and force varying means having an operative connection with said spring means and with said pressure differential responive member for varying the force with which the spring means acts on said valve, and therefore the pressure at which said valve responds, when said pressure differential responsive member is moved from its first position to a second position in response to a pressure differential in said circuits, said force varying means comprising an adjustable abutment which is movable between a normal position and an actuated position in direct consequence of actuating movement of said pressure differential responsive member, means defining a first bore within which said abutment is movable and means defining a second bore extending transversely to said first bore within which said pressure differential responsive member is movable.