General Motors requires that tires used on its vehicles meet certain performance requirements. Since the establishment of this Tire Performance Criteria (TPC) System, tire design, compounding technology, and testing capabilities have improved. Additional performance parameters important to the total tire/vehicle system have been identified and appropriate additional tire performance requirements have been established. Updated TPC test procedures and specifications are presented. Prior to 1984, three generations of TPC specification tires had been developed for General Motors’ vehicles. For 1984 and 1985 model years, development of a fourth generation of TPC specification tires was completed. The considerations which led to establishment of performance goals are discussed. Test data in major tire performance categories is presented in general summary form comparing fourth generation to third generation TPC specification tires. Fourth generation tire performance specifications are contained in the Appendix.