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Vehicle Care 10-57
position it is in. Directional tires
will have an arrow on the tire
indicating the proper direction of
rotation or will have“left”or
“right” molded on the sidewall.
Use this rotation pattern if the
vehicle has different size tires
on the front and rear and they
are non-directional.
Different tire sizes should not be
rotated front to rear.
Use this rotation pattern when
rotating tires of the same size
installed on all four wheel
positions.
If the vehicle has a compact
spare tire, do not include it in the
tire rotation.
Adjust the front and rear tires to
the recommended inflation
pressure on the Tire and
Loading Information label after
the tires have been rotated. See
Tire Pressure on
page 10-50 andVehicle Load
Limits on page 9-11.
Reset the Tire Pressure Monitor
System. See Tire Pressure
Monitor Operation on
page 10-53.
Check that all wheel nuts are
properly tightened. See “Wheel
Nut Torque” underCapacities
and Specifications on
page 12-2.
{Warning
Rust or dirt on a wheel, or on the
parts to which it is fastened, can
make wheel nuts become loose
after time. The wheel could come
off and cause an accident. When
changing a wheel, remove any
rust or dirt from places where the
wheel attaches to the vehicle. In
an emergency, a cloth or a paper
(Continued)
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10-58 Vehicle Care
Warning (Continued)
towel can be used; however, use
a scraper or wire brush later to
remove all rust or dirt.
Lightly coat the center of the
wheel hub with wheel bearing
grease after a wheel change or
tire rotation to prevent corrosion
or rust build-up. Do not get
grease on the flat wheel
mounting surface or on the
wheel nuts or bolts.
When It Is Time for New
Tires
Factors such as maintenance,
temperatures, driving speeds,
vehicle loading, and road conditions
affect the wear rate of the tires.
Treadwear indicators are one way to
tell when it is time for new tires.
Treadwear indicators appear when
the tires have only 1.6 mm (1/16 in)
or less of tread remaining. SeeTire
Inspection on page 10-56 andTire
Rotation on page 10-56.
The rubber in tires ages over time.
This also applies to the spare tire,
if the vehicle has one, even if it is
never used. Multiple factors
including temperatures, loading
conditions, and inflation pressure
maintenance affect how fast aging
takes place. GM recommends that
tires, including the spare if equipped, be replaced after six
years, regardless of tread wear. The
tire manufacture date is the last four
digits of the DOT Tire Identification
Number (TIN) which is molded into
one side of the tire sidewall. The
first two digits represent the week
(01–52) and the last two digits, the
year. For example, the third week of
the year 2010 would have a
four-digit DOT date of 0310.Vehicle Storage
Tires age when stored normally
mounted on a parked vehicle. Park
a vehicle that will be stored for at
least a month in a cool, dry, clean
area away from direct sunlight to
slow aging. This area should be free
of grease, gasoline, or other
substances that can deteriorate
rubber.
Parking for an extended period can
cause flat spots on the tires that
may result in vibrations while
driving. When storing a vehicle for
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Vehicle Care 10-61
Warning (Continued)
specific wheel and tire systems
developed for the vehicle, and
have them properly installed by a
GM certified technician.
See Buying New Tires on
page 10-59 andAccessories and
Modifications on page 10-2.
Uniform Tire Quality
Grading
The following information relates
to the system developed by the
United States National Highway
Traffic Safety Administration
(NHTSA), which grades tires by
treadwear, traction, and
temperature performance. This
applies only to vehicles sold in
the United States. The grades
are molded on the sidewalls of
most passenger car tires. The
Uniform Tire Quality Grading (UTQG) system does not apply
to deep tread, winter tires,
compact spare tires, tires with
nominal rim diameters of
10 to 12 inches (25 to 30 cm),
or to some limited-production
tires.
While the tires available on
General Motors passenger cars
and light trucks may vary with
respect to these grades, they
must also conform to federal
safety requirements and
additional General Motors Tire
Performance Criteria (TPC)
standards.
Quality grades can be found
where applicable on the tire
sidewall between tread shoulder
and maximum section width. For
example:
Treadwear 200 Traction AA
Temperature A
All Passenger Car Tires Must
Conform to Federal Safety
Requirements In Addition To
These Grades.
Treadwear
The treadwear grade is a
comparative rating based on the
wear rate of the tire when tested
under controlled conditions on a
specified government test
course. For example, a tire
graded 150 would wear one and
one-half (1½) times as well on
the government course as a tire
graded 100. The relative
performance of tires depends
upon the actual conditions of
their use, however, and may
depart significantly from the
norm due to variations in driving
habits, service practices and
differences in road
characteristics and climate.