First and second cross-bars extend laterally across the width of a vehicle and are pivotally connected intermediate their lengths in scissors fashion. One end of each cross-bar is pivotally connected to a wheel support assembly which is in turn pivotally connected to the vehicle body by a spring and damper assembly. The other end of the first cross-bar is pivotally connected to the vehicle body by a hydraulic cylinder and piston assembly. The other end of the second cross-bar is pivotally connected via a lever to the actuator of a variable flow hydraulic valve. Lateral forces exerted by the wheels and cross-bars relative to the vehicle body during a turn operate the hydraulic valve to send a proportionate amount of hydraulic fluid to the upper or lower portion of the hydraulic cylinder to thereby prevent rolling of the vehicle body.