Spring rate is one of several factors that affect the ride performance of passenger car tires. A technique has been developed for obtaining precise spring rate measurements in the laboratory under conditions approximating road operation. The spring rate properties of many different tire designs have been measured. The effect of wear and several tire construction variables on spring rate is presented. A correlation between the laboratory measurement of spring rate and vehicle ride evaluations is discussed. It is necessary to measure tire spring rate for the rolling condition with a resonance test technique in order to generate data that are useful for ride performance analyses.