Tire Terminology and DefinitionsAir Pressure: The amount of air inside the tire pressingoutward on each square inch of the tire. Air pressureis expressed in pounds per square inch (psi) orkilopascal (kPa).Accessory Weight: This means the combined weightof optional accessories. Some examples of optionalaccessories are, automatic transmission, power steering,power brakes, power windows, power seats, and airconditioning.Aspect Ratio: The relationship of a tire’s height toits width.Belt: A rubber coated layer of cords that is locatedbetween the plies and the tread. Cords may be madefrom steel or other reinforcing materials.Bead: The tire bead contains steel wires wrapped bysteel cords that hold the tire onto the rim.Bias Ply Tire: A pneumatic tire in which the plies arelaid at alternate angles less than 90 degrees to thecenterline of the tread.Cold Inflation Pressure: The amount of air pressure ina tire, measured in pounds per square inch (psi) before atire has built up heat from driving. See Inflation - TirePressure on page 5-68.Curb Weight: This means the weight of a motorvehicle with standard and optional equipment includingthe maximum capacity of fuel, oil and coolant, butwithout passengers and cargo.DOT Markings: A code molded into the sidewall of atire signifying that the tire is in compliance with theU.S. Department of Transportation motor vehicle safetystandards. The DOT code includes the Tire IdentificationNumber (TIN), an alphanumeric designator which canalso identify the tire manufacturer, production plant,brand and date of production.GVWR: Gross Vehicle Weight Rating, see LoadingYour Vehicle on page 4-33.GAWR FRT: Gross Axle Weight Rating for the frontaxle, see Loading Your Vehicle on page 4-33.GAWR RR: Gross Axle Weight Rating for the rear axle,see Loading Your Vehicle on page 4-33.5-65
