Tire Terminology and DefinitionsAir Pressure: The amount of air inside thetire pressing outward on each square inch ofthe tire. Air pressure is expressed in poundsper square inch (psi) or kilopascal (kPa).Accessory Weight: This means the combinedweight of optional accessories. Some examples ofoptional accessories are, automatic transmission,power steering, power brakes, power windows,power seats, and air conditioning.Aspect Ratio: The relationship of a tire’s heightto its width.Belt: A rubber coated layer of cords that islocated between the plies and the tread. Cordsmay be made from steel or other reinforcingmaterials.Bead : The tire bead contains steel wires wrappedby steel cords that hold the tire onto the rim.Bias Ply Tire: A pneumatic tire in which the pliesare laid at alternate angles less than 90 degreesto the centerline of the tread.Cold Tire Pressure: The amount of air pressurein a tire, measured in pounds per square inch(psi) or kilopascals (kPa) before a tire has builtup heat from driving. See Inflation - Tire Pressureon page 5-58.Curb Weight: The weight of a motor vehiclewith standard and optional equipment includingthe maximum capacity of fuel, oil, and coolant,but without passengers and cargo.DOT Markings: A code molded into the sidewallof a tire signifying that the tire is in compliancewith the U.S. Department of Transportation (DOT)motor vehicle safety standards. The DOT codeincludes the Tire Identification Number (TIN),an alphanumeric designator which can alsoidentify the tire manufacturer, production plant,brand, and date of production.GVWR: Gross Vehicle Weight Rating.See Loading Your Vehicle on page 4-20.GAWR FRT: Gross Axle Weight Rating forthe front axle. See Loading Your Vehicleon page 4-20.5-55
