A method has been developed for determining passenger car tire and wheel uniformity needs by modeling subjective ride ratings. This approach allows consideration of main effects and interactions of all four tire positions on the vehicle. This method has been used to evaluate the impact of various input effects on predicted ride rating distributions. Smooth road shake with first harmonic inputs from the tire/wheel assembly has been addressed. Tire radial force and wheel radial runout first harmonic qualities were examined. Random and matched tire/wheel indexing were considered. Other inputs of interest were assembly balance and assembly vehicle mounting effects.