(F) Uniform Tire Quality Grading (UTQG): Tire
manufacturers are required to grade tires based on
three performance factors: treadwear, traction and
temperature resistance. For more information see
Uniform Tire Quality Grading on page 5-67.
(G) Maximum Cold Inflation Load
Limit
: Maximum load that can be carried and the
maximum pressure needed to support that load.
Tire Size
The following illustration shows an example of a
typical passenger (p-metric) vehicle 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 60,
as shown in item C of the illustration, it would
mean that the tire’s sidewall is 60 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.
5-52
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