(C) Aspect Ratio: A two-digit number thatindicates the tire height-to-width measurements.For example, if the tire size aspect ratio is 60, asshown in item C of the illustration, it would meanthat the tire’s sidewall is 60 percent as high asit is wide.(D) Construction Code: A letter code is used toindicate the type of ply construction in the tire. Theletter R means radial ply construction; the letter Dmeans diagonal or bias ply construction; and theletter B means belted-bias ply construction.(E) Rim Diameter: Diameter of the wheel ininches.(F) Service Description: These charactersrepresent the load index and speed rating of thetire. The load index represents the load carrycapacity a tire is certified to carry. The speedrating is the maximum speed a tire is certified tocarry a load.Tire Terminology and DefinitionsAir Pressure: The amount of air inside the tirepressing outward on each square inch of the tire.Air pressure is expressed in pounds per squareinch (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 is locatedbetween the plies and the tread. Cords may bemade from steel or other reinforcing materials.Bead: The tire bead contains steel wires wrappedby steel cords that hold the tire onto the rim.5-68
