2014 Cadillac CTS Owner Manual - Page 371
2014 Cadillac CTS Manual
Page 371 highlights
Vehicle Care (1) Passenger (P-Metric) Tire: The United States version of a metric tire sizing system. The letter P as the first character in the tire size means a passenger vehicle tire engineered to standards set by the U.S. Tire and Rim Association. (2) Tire Width: The three-digit number indicates the tire section width in millimeters from sidewall to sidewall. (3) Aspect Ratio: A two-digit number that indicates the tire height-to-width measurements. For example, if the tire size aspect ratio is 60, as shown in item 3 of the illustration, it would mean that the tire's sidewall is 60 percent as high as it is wide. (4) 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. (5) Rim Diameter : Diameter of the wheel in inches. (6) Service Description: These characters represent the load index and speed rating of the tire. The load index represents the load carrying capacity a tire is certified to carry. The speed rating is the maximum speed a tire is certified to carry a load. 10-67 Accessory Weight: The combined weight of optional accessories. Some examples of optional accessories are automatic transmission, power windows, power seats, and air conditioning. Aspect Ratio: The relationship of a tire's height to its width. Belt: A rubber coated layer of cords between the plies and the tread. Cords may be made from steel or other reinforcing materials. Bead: The tire bead contains steel wires wrapped by steel cords that hold the tire onto the rim. Bias Ply Tire: A pneumatic tire in which the plies are laid at alternate angles less than 90 degrees to the centerline of the tread. 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).