PURPOSE: To excellently maintain the rectilinear advancing ability of a vehicle even if a tire supported through a vehicle suspension moves vertically during the rectilinear running of the vehicle.
CONSTITUTION: In setting the characteristic of the variation of a toe angle caused by the vertical movement of a tire to a car body of a vehicle suspension, the characteristic of the variation of the towing angle is set up so that the toe angle may vary with the vertical movement of the tire so as to cancel the change of the cornering force of the tire based on the change ΔW of a tire load due to the vertical movement of the tire to the car body during the running of a vehicle by the change of the cornering force of the tire based on the change ΔSA of a slip angle due to the change of the toe angle of the tire.