Tire SizeThe following illustration shows an example of a typicalpassenger vehicle tire size.(A) Passenger (P-Metric) Tire: The United Statesversion of a metric tire sizing system. The letter P asthe first character in the tire size means a passengervehicle tire engineered to standards set by the U.S. Tireand Rim Association.(B) Tire Width: The three-digit number indicates thetire section width in millimeters from sidewall to sidewall.(C) Aspect Ratio: A two-digit number that indicates thetire height-to-width measurements. For example,if the tire size aspect ratio is 60, as shown in item C ofthe illustration, it would mean that the tire’s sidewallis 60 percent as high as it is wide.(D) Construction Code: A letter code is used to indicatethe type of ply construction in the tire. The letter R meansradial ply construction; the letter D means diagonal orbias ply construction; and the letter B means belted-biasply 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. Thespeed rating is the maximum speed a tire is certifiedto carry a load. Speed ratings range from A to Z.5-57
