Abstract: A caster wheel supporting arrangement including anti-shimmy means which is particularly useful for vehicles in which the caster wheels may be orientated at different angles to the parts supported thereby during normal forward movement of the vehicle. Such a situation occurs in large airport runway sweepers where the broom frame, which is supported by caster wheels, may be set at varying orientations to the normal sweeper direction. The support arrangement includes a rotary hydraulic pump, preferably of the gerotor type, the rotor of which is connected to rotate with the caster wheel bracket, and a hydraulic circuit connects the ports of the pump, this circuit including a pressure sensitive flow resisting device which opens to increase the flow area therethrough with increasing pressure difference between the pump ports.