Knowledge of that component of a vehicle's handling characteristics represented by the vehicle dynamics is necessary to analyze the driver's role in controlling the vehicle. One aspect of this problem is determination of the effect on the stability under differing road conditions in the linear as well as nonlinear region. The simulation presented evaluates the response the vehicle suspension system to suddenly applied external impulses which are identified as caused by wind gust and road disturbance. This analysis considers only the effect on the lateral stability of the vehicle. Thus this representation is assumed completely decoupled from the longitudinal dynamics of the vehicle. Proceeding in this fashion makes it possible to study the effect of large wind gust and lateral road impacts on the lateral stability of a vehicle containing nonlinear tire characteristics. The effects in the nonlinear region are clearly demonstrated with the aid of a conventional root locus plot.