Vehicle Care 9-71Uniform Tire QualityGradingQuality grades can be foundwhere applicable on the tiresidewall between tread shoulderand maximum section width. Forexample:Treadwear 200 Traction AATemperature AThe following information relatesto the system developed by theUnited States National HighwayTraffic Safety Administration(NHTSA), which grades tires bytreadwear, traction, andtemperature performance. Thisapplies only to vehicles sold inthe United States. The gradesare molded on the sidewalls ofmost passenger car tires. TheUniform Tire Quality Grading(UTQG) system does not applyto deep tread, winter-type snowtires, space-saver, or temporaryuse spare tires, tires withnominal rim diameters of10 to 12 inches (25 to 30 cm),or to some limited-productiontires.While the tires available onGeneral Motors passenger carsand light trucks may vary withrespect to these grades, theymust also conform to federalsafety requirements andadditional General Motors TirePerformance Criteria (TPC)standards.All Passenger Car Tires MustConform to Federal SafetyRequirements In Addition ToThese Grades.TreadwearThe treadwear grade is acomparative rating based on thewear rate of the tire when testedunder controlled conditions on aspecified government testcourse. For example, a tiregraded 150 would wear one anda half (1½) times as well on thegovernment course as a tiregraded 100. The relativeperformance of tires dependsupon the actual conditions oftheir use, however, and maydepart significantly from thenorm due to variations in drivinghabits, service practices anddifferences in roadcharacteristics and climate.