Abstract: A vehicle wheel suspension system includes a suspension device having a double acting hydraulic actuator, of which the piston position is adjustable in response to forces acting on the piston and/or to a selective control input, and a load bearing strut operable in response to the actuator piston experience to minimize the actuator load. The device comprises an inner member having a portion slidable within an outer member with the piston on the inner member and slidably engaging the outer member and a fluid body operative between the members, the volume of which is selectively adjustable to alter and strut pre-load and load deflection characteristics. The fluid body may be a body of oil or a gas.

Abstract: A vehicle suspension system comprises suspension units (2) with double acting hydraulic actuators (12) for carrying the road wheels (4). Signals from transducers sensing actuator load and actuator piston position (14,15) are used in a control system (5) to generate signals representing forces corresponding to heave, pitch, roll and warp modes of vehicle movement and control signals are generated for supply to servo-valves (18) associated with the actuators to obtain desired vehicle attitude. The control signals can be modified by signals representing vehicle speed and lateral and longitudinal acceleration and under selective control of the driver.