A hydraulic system for a suspension system for a vehicle includes at least one first pair of wheel rams (11, 12) at a first end of the vehicle and at least one second pair of wheel rams (13, 14) at a second end of the vehicle, each rams including a compression chamber (45-48) and a rebound chamber (49-52); and the system includes first and second diagonal circuits with respect to said vehicle. The hydraulic system includes at least one first and second modal resilience devices (81, 82). These devices each including at least one resilient means (107-110), at least one moveable member (105-106) and at least first and second (89, 90 and 91, 92) system modal chambers. Motion of the moveable member of each modal resilience device due to roll or pitch motion of the vehicle is controlled by the respective at least one resilient means to thereby provide respective roll or pitch resilience in the system.