Abstract: IDetailed calculations have been made on the dynamics of four-axle pwoer cars with motor mounted on frame. The numerical results show that the frame masses between the primary and the secondary suspensions influence the riding quality greatly. It is very important to set an appropriate secondary lateral stop clearance, and the influences of damping of the secondary suspension to the riding quality is related to the stiffness of the secondary suspension. It is also necessary for the parameters of yaw dampers to match those of lateral dampers to achieve good hunting stability.