Tire size – GMC 2004 Canyon User Manual
Page 325
(F) Tire Size: A combination of letters and numbers
define a tire’s width, height, aspect ratio, construction
type and service description. The letter “T” as the
first character in the tire size means the tire is for
temporary use only.
(G) TPC Spec (Tire Performance Criteria
Specification): Original equipment tires designed to
GM’s specific tire performance criteria have a TPC
specification code molded onto the sidewall. GM’s TPC
specifications meet or exceed all federal safety
guidelines.
Tire Size
The following examples show the different parts of a
tire size.
(A) 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.
(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 illustration, it would mean that the tire’s sidewall
is 75% as high as it is wide.
(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) Service Description: The service description
indicates the load range and speed rating of a tire.
The load index can range from 1 to 279. Speed ratings
range from A to Z.
Passenger (P-Metric) Tire
5-61