1999 GMC Sierra 1500 Pickup Owner's Manual - Page 359

r CAUTION If you operate your vehicle with a tire that is badly underinflated, the tire canoverheat. Anoverheatedtirecanloseairsuddenlyor catcl. fire. Youor others could beinjured.Besurealltires(includingthe spare, if any) are properlyinflated. I Buying New Tires To find outwhat kind and size of tires you need, look at the Certificationflire label.Thetires installed onyourvehiclewhen it wasnewhadaTire Performance Criteria Specification(TPCSpec)numberoneachtire'ssidewall. Whenyougetnewtires,getoneswiththatsameTPCSpecnumber.That way,your vehicle will continue to have tires that are designed to give proper endurance,handling,speedrating,traction,rideandotherthingsduring normalserviceonyourvehicle. Ifyour tires haveanall-seasontreaddesign, "MS" (formudandsnow). the TPCnumberwillbefollowedbya If youeverreplaceyour tires withthosenothavingaTPCSpecnumber, makesuretheyarethesamesize, load range,speedratingandconstruction type(bias,bias-belted or radial) as youroriginaltires. 1 CAUTION I * Mixingtirescouldcauseyou to losecontrolwhiledriving. If youmix ) tires of different sizes ortypes (radialand bias-belted tires),the vehicle maynothandleproperly,andyoucouldhaveacrash.Be sure to useand sameall the type size wheels. tires on I Uniform Tire Qua/ity Grading Thefollowinginformationrelates to the systemdevelopedbytheUnited StatesNationalHighwayTrafficSafetyAdministrationwhichgradestiresby treadwear,tractionandtemperatureperformance.(Thisappliesonlyto vehicles sold in theUnited States.) Treadwear Thetreadweargrade is acomparativeratingbasedonthewearrate of the tire whentestedundercontrolledconditionsonaspecifiedgovernment test (1 1/2) course. Forexample,a tire graded 150 wouldwearoneandahalf timesaswellonthegovernmentcourse as a tire graded 100. Therelative of their use, performance of tiresdependsupontheactualconditions however,andmaydepartsignificantlyfromthenormduetovariations in drivinghabits,servicepracticesanddifferences in roadcharacteristicsand climate. 6-81