EFFECT OF THE NORMAL FORCE DEPENDENCE OF CORNERING STIFFNESS ON THE LATERAL STABILITY OF RECREATIONAL VEHICLES

A study of tire cornering stiffness makes use of Bergman's quadratic expression relating cornering stiffness and normal load by correlating tire test data from four different sources. This quadratic expression, as well as linear and constant approximations of it, are used in lateral stability analyses of a car and of a car/trailer system. It is shown that the change in cornering stiffness with normal load significantly affects critical speed. Parameters other than cornering stiffness also change with changes in normal loads: e.g. roll steer, aligning torque, and camber stiffness. These variations may have to be included in order to obtain valid lateral stability information.