A method of controlling the roll stiffness and roll moment distribution of a vehicle suspension system of a vehicle, the vehicle suspension system including front and rear vehicle support means for supporting the vehicle and any load carried by the vehicle, and at least one roll moment reaction means for providing a variable roll stiffness for the vehicle suspension system;The method including the step of adjusting the roll stiffness and the roll moment distribution of the vehicle suspension system in dependence on the load carried by at least a rear or front of the vehicle.