Suspension system (10) includes a compressible fluid (12), a suspension strut (14), a hydraulic cavity (16), a reservoir (18), and a volume modulator (20). The hydraulic cavity (16) is at least partially defined by the suspension strut (14) and is adapted to contain a portion of the compressible fluid (12). The hydraulic cavity (16) and the compressible fluid (12) supply a suspending spring force that biases a wheel (22) of a vehicle toward the road surface. The volume modulator (20) selectively pushes the compressible fluid (12) into the hydraulic cavity (16) and vents the compressible fluid (12) from the hydraulic cavity (16), thereby actively modulating the suspending spring force.