Vehicle suspension spring system

A vehicle attitude control system for a vehicle having a plurality of wheel stations including:

• a strut assembly at each wheel station,
• each strut assembly having an hydraulic cylinder with a piston which divides the cylinder volume into a main oil volume and an annular oil volume,
• said main oil volume communicating via a first oil passage with an associated first accumulator having a main gas volume,
• said annular oil volume communicating via a second oil passage with an associated second accumulator having an auxiliary gas volume,
• the oil in each accumulator being separated from the gas by a separator piston or diaphragm,
• a third oil passage with an isolating valve which interconnects said first and second oil passages,
• means for switching the isolating valve between open and closed positions,
• said struts being connected to a common controller and sensing means,
• the sensing means for sensing one or more vehicle attitude parameters,
• said sensing means being connected to the controller which is operable for independently switching the isolating valve of each strut between open and closed positions for independently altering spring stiffness of each strut in response lo said sensed vehicle attitude parameter or parameters,
• wherein the controller includes means for inferring a lateral acceleration of the vehicle from a sensed vehicle speed and steer angle and a solenoid actuated dual rate hydro-pneumatic suspension strut at each wheel station of the vehicle,
• the controller being operable to engage a required spring rate at each wheel station to counter body roll induced by the said lateral acceleration.