GMC 2009 Sierra - Manual (Page 386)

The rubber in tires degrades over time, even if they
are not being used. This is also true for the spare tire,
if your vehicle has one. Multiple conditions affect
how fast this aging takes place, including temperatures,
loading conditions, and inflation pressure maintenance.
With proper care and maintenance tires will typically
wear out before they degrade due to age. If you
are unsure about the need to replace your tires as
they get older, consult the tire manufacturer for
more information.
Buying New Tires
GM has developed and matched specific tires for
your vehicle. The original equipment tires installed
on your vehicle, when it was new, were designed
to meet General Motors Tire Performance Criteria
Specification (TPC spec) system rating. If you need
replacement tires, GM strongly recommends that you
get tires with the same TPC Spec rating. This way,
your vehicle will continue to have tires that are
designed to give the same performance and vehicle
safety, during normal use, as the original tires.
GM’s exclusive TPC Spec system considers over a
dozen critical specifications that impact the overall
performance of your vehicle, including brake system
performance, ride and handling, traction control, and
tire pressure monitoring performance. GM’s TPC Spec
number is molded onto the tire’s sidewall near the
tire size. If the tires have an all-season tread design,
the TPC spec number will be followed by an MS for mud
and snow. See Tire Sidewall Labeling on page 5-59
for additional information.
GM recommends replacing tires in sets of four. This
is because uniform tread depth on all tires will help
keep your vehicle performing most like it did when the
tires were new. Replacing less than a full set of tires can
affect the braking and handling performance of your
vehicle. See Tire Inspection and Rotation on page 5-72
for information on proper tire rotation.
5-74