A reduction in vehicle weight sometimes results in a reduction in truck body torsional stiffness. Hence, the authors investigate the influence of vehicle body torsional stiffness on vehicle controllability and stability. A simulation analysis and vehicle test are carried out on a medium-duty truck, and the frequency response characteristics of the vehicle are studied by changing vehicle design parameters. The results show that a reduction in body torsional stiffness does not affect the yaw and lateral characteristics of vehicle motion, but increases the steady state gain of the front roll angle. Accordingly, even if body torsional stiffness is unavoidably lowered, appropriate controllability and stability can be maintained by increasing the roll stiffness of the front suspension, thereby reducing the front roll angle.