Cadillac 2011 CTS Coupe Owner's Manual page 388

Many General Motors high
performance models come
factory equipped with tires that
are optimized for maximum dry
and wet road performance while
still retaining satisfactory tread
life, excellent durability, and low
noise levels. In severe winter
climates where snowfall may be
significant, these tires may be
found to provide less traction.
Useful information about a tire
is molded into its sidewall. The
examples below show a typical
passenger vehicle tire and a
compact spare tire sidewall.
The tire size is
a combination of letters and
numbers used to define a
particular tire's width, height,
aspect ratio, construction type,
and service description. See the
Tire Size illustration later in this
section for more detail.
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
Department of Transportation
(DOT) code indicates that
the tire is in compliance
with the U.S. Department of
Transportation Motor Vehicle
Safety Standards.