Tire SizeThe following illustration shows an example of atire size.(A) P-Metric Tire: The United States version ofa metric tire sizing system. The letter P as thefirst character in the tire size means a passengervehicle tire engineered to standards set by theU. S. Tire and Rim Association.(B) Tire Width: The three-digit number indicatesthe tire section width in millimeters from sidewallto sidewall.(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.5-53
