Chevrolet 2011 Express 1500 Cargo Owner's Manual page 326

of cord and number of plies in
the sidewall and under the tread.
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
and
.
The type
The following examples show
the different parts of a tire size.
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.
The three digit
number indicates the tire section
width in millimeters from
sidewall to sidewall.
A two digit
number that indicates the tire
height to width measurements.
For example, if the tire size
aspect ratio is 75, as shown in
item C of the illustration, it would
mean that the tire's sidewall is
75 percent as high as it is wide.
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.