Cadillac 2008 DTS Owner's Manual page 349

(G) Single Tire Maximum Load
that can be carried and the maximum pressure
needed to support that load when used as a single.
For information on recommended tire pressure
see Inflation - Tire Pressure on page 5-58.
Tire Size
The following illustration shows an example of
a 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.
(B) Tire Width The three-digit number indicates
:
the tire section width in millimeters from sidewall
to sidewall.
5-54
Maximum load
:
(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
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
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
:
These characters
: