Abstract: Every pressure vessel is connected by the agency of a connection channel to a control chamber. In both connection channels a shut-off valve is provided. The control chamber comprises a spring bellows whereby a spring counteracts a pressure force acting onto the mean area of said spring bellows. A ring is arranged on a control rod which controls the position of said shut-off valves. Upon a pressure loss in one of the pressure vessels the control rod operates the shut-off valves into their shut-off position such that upon a later pressure rise in one of the pressure vessels these shut-off valves remain closed. This ensures that upon a later pressure rise in an undamaged of the two pressure vessels such will remain separated from the damaged one. This pressure control means is preferably used in a motor vehicle having twin tires such as a truck or bus.