In the design of car suspension system, handling and stability should always be considered. The understeer gradient, defined in steady-state cornering, is directly related to these performance. Therefore, it is very important to know the understeer gradient characteristics.
The design variables of suspension system are anti-roll bars, bushes, hard points, and so on. The purpose of this paper is to show the influence on understeer gradient by design variables of car suspension system. Dynamic analysis for varying design variables was performed by ADAMS, the commercial simulation software of multi-body system. This simulation is based on the constant speed method, which is one of the experimental measurement tests of understeer gradient.
The cornering forces of tire are dependent on, and nolinear with, load. More roll moment on the front axles contributes to understeer, whereas more roll moment on the rear axles contributes to oversteer. The result is to show decrease in understeer gradient as reducing front anti-roll bar stiffness, and increase as reducing rear anti-roll bar stiffness. Hard points are related steer angle. Tie-rod points make more contribution by changing toe angle.
