A hydropneumatic system for suspensions of vehicle wheel assemblies is provided, for each suspension, with a respective hydropneumatic cylinder having a first and a second body, which can move axially relative to each other and define respective chambers, axially separated from each other via a piston element; the latter is coupled in a fluid-tight manner to the second body and floats between two stroke end positions in response to the pressures in the two chambers; the two chambers of each hydropneumatic cylinder communicate respectively with a hydraulic supply line and with a pneumatic supply line; the system further has a pressurization device which sets the pressure in the pneumatic supply line to a value at least equal to the pressure in the hydraulic supply line.