(C) Aspect Ratio: A two-digit number that indicates thetire height-to-width measurements. For example,if the tire size aspect ratio is “70,” as shown in item “C”of the illustration, it would mean that the tire’s sidewallis 70% as high as it is wide.(D) Construction Code: A letter code is used toindicate the type of ply construction in the tire. The letter“R” means radial ply construction; the letter “D” meansdiagonal or bias ply construction; and the letter “B”means belted-bias ply construction.(E) Rim Diameter: Diameter of the wheel in inches.(F) Service Description: These characters representthe load range and speed rating of the tire. The loadindex represents the load carry capacity a tire is certifiedto carry. The load index can range from 1 to 279.The speed rating is the maximum speed a tire is certifiedto carry a load. Speed ratings range from “A” to “Z”.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.5-63
