(C) Aspect Ratio : A two-digit number thatindicates the tire height-to-width measurements.For example, if the tire size aspect ratio is 60,as shown in item C of the illustration, it wouldmean that the tire’s sidewall is 60 percent ashigh 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 means diagonal or bias plyconstruction; and the letter B means belted-biasply construction.(E) Rim Diameter: Diameter of the wheel ininches.(F) Service Description: These charactersrepresent the load range and speed rating of thetire. The load index represents the load carrycapacity a tire is certified to carry. The load indexcan range from 1 to 279. The speed rating isthe maximum speed a tire is certified to carry aload. Speed ratings range from A to Z.Tire Terminology and DefinitionsAir Pressure: The amount of air inside thetire pressing outward on each square inch of thetire. Air pressure is expressed in pounds persquare 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.5-64
