Buick Enclave Owner's Manual page 300

Maximum load that
can be carried and the
maximum pressure needed to
support that load.
The
temporary use tire or compact
spare tire should be inflated to
420 kPa (60 psi). For more
information on tire pressure and
inflation see
.
A combination of
letters and numbers define a
tire's width, height, aspect ratio,
construction type, and service
description. The letter T as the
first character in the tire size
means the tire is for temporary
use only.
Original
equipment tires designed to
GM's specific tire performance
criteria have a TPC specification
code molded onto the sidewall.
GM's TPC specifications meet or
exceed all federal safety
guidelines.
The following is an example of a
typical passenger vehicle
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 60, as shown in
item 3 of the illustration, it would
mean that the tire's sidewall is
60 percent as high as it is wide.
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.
A letter