Cadillac 2008 DTS - Manual (Page 348)

(G) Single Tire Maximum Load : 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.
(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.
5-54