9-56 Vehicle CareTire Terminology andDefinitionsAir Pressure : The amount ofair inside the tire pressingoutward on each square inch ofthe tire. Air pressure isexpressed in psi (pounds persquare inch) or kPa (kilopascal).Accessory Weight : Thismeans the combined weight ofoptional accessories. Someexamples of optionalaccessories are, automatictransmission, power steering,power brakes, power windows,power seats, and airconditioning.Aspect Ratio : The relationshipof a tire's height to its width.Belt : A rubber coated layer ofcords that is located betweenthe plies and the tread. Cordsmay be made from steel or otherreinforcing materials.Bead : The tire bead containssteel wires wrapped by steelcords that hold the tire ontothe rim.Bias Ply Tire : A pneumatic tirein which the plies are laid atalternate angles less than90 degrees to the centerline ofthe tread.Cold Tire Pressure : Theamount of air pressure in a tire,measured in psi (pounds persquare inch) or kPa (kilopascal)before a tire has built up heatfrom driving. See Tire Pressureon page 9‑59.Curb Weight : The weight of amotor vehicle with standard andoptional equipment including themaximum capacity of fuel, oil,and coolant, but withoutpassengers and cargo.DOT Markings : A code moldedinto the sidewall of a tiresignifying that the tire is incompliance with the U.S.Department of Transportation(DOT) motor vehicle safetystandards. The DOT codeincludes the Tire IdentificationNumber (TIN), an alphanumericdesignator which can alsoidentify the tire manufacturer,production plant, brand, anddate of production.GVWR : Gross Vehicle WeightRating. See Vehicle Load Limitson page 8‑11.
