Tire Size - Chevrolet 2005 Equinox Owner's Manual

(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 illustration shows an example of a typical
passenger vehicle tire size.
(A) 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.
5-50
(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 70, as shown in item C of
the illustration, it would mean that the tire's sidewall is
70 percent 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: These characters represent
the load range and speed rating of the tire. The load
index represents the load carry capacity a tire is certified
to carry. The load index can range from 1 to 279. The
speed rating is the maximum speed a tire is certified
to carry a load. Speed ratings range from A to Z.