2012 GMC Sierra Owner's Manual - Page 441

Vehicle Care (LT‐Metric) tire illustration, it would mean that the tire's sidewall is 75 percent as high as it is wide. Light Truck (LT‐Metric) Tire 10-55 (single/dual). The speed rating is the maximum speed a tire is certified to carry a load. (A) Light Truck (LT‐Metric) Tire: The United States version of a metric tire sizing system. The letters LT as the first two characters in the tire size mean a light truck tire engineered to standards set by the U.S. Tire and Rim Association. (B) Tire Width: The three‐digit number indicates the tire section width in millimeters from sidewall to sidewall. (C) Aspect Ratio: A two‐digit number that indicates the tire height‐to‐width measurements. For example, if the tire size aspect ratio is 75, as shown in item C of the light truck (D) Construction Code: A letter code is used to indicate the type of ply construction in the tire. The letter R means radial ply construction; the letter D means diagonal or bias ply construction; and the letter B means belted‐bias ply construction. (E) Rim Diameter : Diameter of the wheel in inches. (F) Load Range: Load Range. (G) Service Description: The service description indicates the load index and speed rating of a tire. If two numbers are given as in the example, 120/116, then this represents the load index for single versus dual wheel usage Tire Terminology and Definitions Air Pressure: The amount of air inside the tire pressing outward on each square inch of the tire. Air pressure is expressed in kPa (kilopascal) or psi (pounds per square inch). Accessory Weight: The combined weight of optional accessories. Some examples of optional accessories are automatic transmission, power steering, power brakes, power windows, power seats, and air conditioning. Aspect Ratio: The relationship of a tire's height to its width.