Abstract: A lift axle suspension for a tandem trailer has first and second suspension air bags for first and second axles. There is a lift air bag that, when pressurized, applies a lifting force to lift the second axle relative to the first axle. A first pneumatic circuit supplies compressed air to the first suspension air bag and a diverter valve and is controlled by a height selector valve that is opened and closed based on the ride height of the trailer. The diverter valve selectively supplies compressed air to the second suspension air bag and a pressure regulator that limits air pressure to a predetermined pressure. A second pneumatic supplies compressed air to the lift air bag and is controlled by a pilot valve.

Abstract: A lift axle suspension for a tandem trailer has first and second suspension air bags for first and second axles. There is a lift air bag that, when pressurized, applies a lifting force to lift the second axle relative to the first axle. A first pneumatic circuit supplies compressed air to the first suspension air bag and a diverter valve and is controlled by a height selector valve that is opened and closed based on the ride height of the trailer. The diverter valve selectively supplies compressed air to the second suspension air bag and a pressure regulator that limits air pressure to a predetermined pressure. A second pneumatic supplies compressed air to the lift air bag and is controlled by a pilot valve.

Abstract: A height control valve linkage assembly for an air suspension system, including an air bag and a height control valve controlling the supply of air to the air bag. A telescopic linkage is positioned between the arm of the height control valve and the suspension. The linkage is extended to alter the ride height setting of the height control valve, thereby selectively providing additional clearance.