VEHICLE CARE 305Treadwear indicators are one way totell when it is time for new tires.Treadwear indicators appear when thetires have only 1.6 mm (1/16 in) orless of tread remaining. See TireInspection 0 303 and Tire Rotation0 303.The rubber in tires ages over time.This also applies to the spare tire,if the vehicle has one, even if it isnever used. Multiple factors includingtemperatures, loading conditions, andinflation pressure maintenance affecthow fast aging takes place. GMrecommends that tires, including thespare if equipped, be replaced after sixyears, regardless of tread wear. Thetire manufacture date is the last fourdigits of the DOT Tire IdentificationNumber (TIN) which is molded intoone side of the tire sidewall. The firsttwo digits represent the week (01–52)and the last two digits, the year. Forexample, the third week of the year2010 would have a four-digit DOTdate of 0310.Vehicle StorageTires age when stored normallymounted on a parked vehicle. Park avehicle that will be stored for at leasta month in a cool, dry, clean areaaway from direct sunlight to slowaging. This area should be free ofgrease, gasoline, or other substancesthat can deteriorate rubber.Parking for an extended period cancause flat spots on the tires that mayresult in vibrations while driving.When storing a vehicle for at least amonth, remove the tires or raise thevehicle to reduce the weight from thetires.Buying New TiresGM has developed and matchedspecific tires for the vehicle. Theoriginal equipment tires installedwere designed to meet GeneralMotors Tire Performance CriteriaSpecification (TPC Spec) systemrating. When replacement tires areneeded, GM strongly recommendsbuying tires with the same TPCSpec rating.GM's exclusive TPC Spec systemconsiders over a dozen criticalspecifications that impact theoverall performance of the vehicle,including brake systemperformance, ride and handling,traction control, and tire pressuremonitoring performance. GM'sTPC Spec number is molded ontothe tire's sidewall near the tiresize. If the tires have an all-seasontread design, the TPC Specnumber will be followed by MS formud and snow. See Tire SidewallLabeling 0 293, for additionalinformation.GM recommends replacing worntires in complete sets of four.Uniform tread depth on all tireswill help to maintain theperformance of the vehicle.Braking and handling performancemay be adversely affected if all thetires are not replaced at the sametime. If proper rotation andmaintenance have been done, allfour tires should wear out at
