Vehicle Care 9-55Tire DesignationsTire SizeThe following illustration showsan example of a typicalpassenger vehicle tire size.(A) Passenger (P‐Metric) Tire :The United States version of ametric tire sizing system. Theletter P as the first character inthe tire size means a passengervehicle tire engineered tostandards set by the U.S. Tireand Rim Association.(B) Tire Width : The three‐digitnumber indicates the tire sectionwidth in millimeters fromsidewall to sidewall.(C) Aspect Ratio : A two‐digitnumber that indicates the tireheight‐to‐width measurements.For example, if the tire sizeaspect ratio is 60, as shown initem C of the illustration, it wouldmean that the tire's sidewall is60 percent as high as it is wide.(D) Construction Code : Aletter code is used to indicatethe type of ply construction inthe tire. The letter R meansradial ply construction; theletter D means diagonal or biasply construction; and the letter Bmeans belted‐bias plyconstruction.(E) Rim Diameter : Diameter ofthe wheel in inches.(F) Service Description : Thesecharacters represent the loadindex and speed rating of thetire. The load index representsthe load carry capacity a tire iscertified to carry. The speedrating is the maximum speed atire is certified to carry a load.
