1993 GMC Suburban Owner's Manual - Page 319

I TREAD WEAR INDICATORS #I656 Oneway to tell whenit'stimefornewtires is to checkthetreadwear indicators,whichwillappearwhenyourtireshaveonly 2/32 inch (1.6 mm)or less of treadremaining. You need anew tire if: Q You can seethe indicators atthreeplacesaroundthe tire. to show You can see cord or fabricshowingthroughthetire'srubber. * The tread orsidewalliscracked,cutorsnaggeddeepenough cord or fabric. e The tire has a bump, bulge orsplit. The tire has apuncture, cut, or otherdamagethatcan'tberepairedwell because of thesizeor location of thedamage. e Bwying Mew TWes To find outwhat kind and size of tires youneed,lookatthe Certificationnire label.Thetires installed on yourvehiclewhen it wasnew had aTire PerformanceCriteriaSpecification(TPCSpec)number on eachtire'ssidewall. Whenyougetnew tires, getoneswiththatsameTPCSpecnumber.That way,yourvehiclewill continue to havetiresthataredesigned to giveproper endurance,handling,speedrating,traction,ride and otherthings during normal service on yourvehicle. If yourtireshave an all-season tread design, theTPCnumberwill be followed bya "MS" (for mud and snow). 6-53