Pontiac Solstice 2008 Owner's Manual page 250

(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 5-70.
(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
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.
5-54
:
:
The United States
:
(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
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
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.
A letter code is used to
:
These characters
: