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Belt:A rubber coated layer of cords that is located
between the plies and the tread. Cords may be made
from steel or other reinforcing materials.
Bead:The tire bead contains steel wires wrapped by
steel cords that hold the tire onto the rim.
Bias Ply Tire:A pneumatic tire in which the plies are
laid at alternate angles less than 90 degrees to the
centerline of the tread.
Cold In ation Pressure:The amount of air pressure in
a tire, measured in pounds per square inch (psi) or
kilopascals (kPa) before a tire has built up heat
from driving. SeeInflation - Tire Pressure on page 5-56.
Curb Weight:This means the weight of a motor
vehicle with standard and optional equipment including
the maximum capacity of fuel, oil and coolant, but
without passengers and cargo.
DOT Markings:A code molded into the sidewall of a
tire signifying that the tire is in compliance with the U.S.
Department of Transportation (DOT) motor vehicle
safety standards. The DOT code includes the Tire
Identification Number (TIN), an alphanumeric designator
which can also identify the tire manufacturer, production
plant, brand and date of production.
GVWR:Gross Vehicle Weight Rating, seeLoading
Your Vehicle on page 4-28.GAWR FRT:Gross Axle Weight Rating for the front
axle, seeLoading Your Vehicle on page 4-28.
GAWR RR:Gross Axle Weight Rating for the rear axle,
seeLoading Your Vehicle on page 4-28.
Intended Outboard Sidewall:The side of an
asymmetrical tire, that must always face outward when
mounted on a vehicle.
Kilopascal (kPa):The metric unit for air pressure.
Light Truck (LT-Metric) Tire:A tire used on light duty
trucks and some multipurpose passenger vehicles.
Load Index:An assigned number ranging from
1 to 279 that corresponds to the load carrying capacity
of a tire.
Maximum In ation Pressure:The maximum air
pressure to which a cold tire may be inflated. The
maximum air pressure is molded onto the sidewall.
Maximum Load Rating:The load rating for a tire at the
maximum permissible inflation pressure for that tire.
Maximum Loaded Vehicle Weight:The sum of curb
weight; accessory weight; vehicle capacity weight;
and production options weight.
Normal Occupant Weight:The number of occupants a
vehicle is designed to seat multiplied by 150 lbs (68 kg).
SeeLoading Your Vehicle on page 4-28.
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Occupant Distribution:Designated seating positions.
Outward Facing Sidewall:The side of an asymmetrical
tire that has a particular side that faces outward when
mounted on a vehicle. The side of the tire that contains a
whitewall, bears white lettering, or bears manufacturer,
brand, and/or model name molding that is higher or
deeper than the same moldings on the other sidewall of
the tire.
Passenger (P-Metric) Tire:A tire used on passenger
cars and some light duty trucks and multipurpose
vehicles.
Recommended In ation Pressure:Vehicle
manufacturer’s recommended tire inflation pressure and
shown on the tire placard. SeeInflation - Tire Pressure on
page 5-56andLoading Your Vehicle on page 4-28.
Radial Ply Tire:A pneumatic tire in which the ply cords
that extend to the beads are laid at 90 degrees to the
centerline of the tread.
Rim:A metal support for a tire and upon which the tire
beads are seated.
Sidewall:The portion of a tire between the tread and
the bead.
Speed Rating:An alphanumeric code assigned to a tire
indicating the maximum speed at which a tire can
operate.
Traction:The friction between the tire and the road
surface. The amount of grip provided.Tread:The portion of a tire that comes into contact
with the road.
Treadwear Indicators:Narrow bands, sometimes
called wear bars, that show across the tread of a tire
when only 1/16 inch (1.6 mm) of tread remains.
SeeWhen It Is Time for New Tires on page 5-58.
UTQGS (Uniform Tire Quality Grading Standards):
A tire information system that provides consumers
with ratings for a tire’s traction, temperature, and
treadwear. Ratings are determined by tire manufacturers
using government testing procedures. The ratings are
molded into the sidewall of the tire. SeeUniform
Tire Quality Grading on page 5-60.
Vehicle Capacity Weight:The number of designated
seating positions multiplied by 150 lbs (68 kg) plus the
rated cargo load. SeeLoading Your Vehicle on
page 4-28.
Vehicle Maximum Load on the Tire:Load on an
individual tire due to curb weight, accessory weight,
occupant weight, and cargo weight.
Vehicle Placard:A label permanently attached to a
vehicle showing the vehicle’s capacity weight and the
original equipment tire size and recommended inflation
pressure. See “Tire and Loading Information Label” under
Loading Your Vehicle on page 4-28.
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In ation - Tire Pressure
Tires need the correct amount of air pressure to operate
effectively.
Notice:Do not let anyone tell you that
under-in ation or over-in ation is all right. It is not.
If your tires do not have enough air (under-in ation),
you can get the following:
Too much exing
Too much heat
Tire overloading
Premature or irregular wear
Poor handling
Reduced fuel economy
If your tires have too much air (over-in ation), you
can get the following:
Unusual wear
Poor handling
Rough ride
Needless damage from road hazardsA vehicle specific tire and loading information label is
attached to your vehicle. This label shows your vehicle’s
original equipment tires and the correct inflation
pressures for your tires when they are cold. The
recommended cold tire inflation pressure, shown on the
label, is the minimum amount of air pressure needed to
support your vehicle’s maximum load carrying capacity.
For additional information regarding how much weight
your vehicle can carry, and an example of the tire
and loading information label, seeLoading Your Vehicle
on page 4-28. How you load your vehicle affects
vehicle handling and ride comfort, never load your
vehicle with more weight than it was designed to carry.
When to Check
Check your tires once a month or more. Do not forget to
check the compact spare tire. For additional information
regarding the compact spare tire, seeCompact
Spare Tire on page 5-73.
How to Check
Use a good quality pocket-type gage to check tire
pressure. You cannot tell if your tires are properly inflated
simply by looking at them. Radial tires may look properly
inflated even when they are under-inflated. Check the
tire’s inflation pressure when the tires are cold. Cold
means your vehicle has been sitting for at least
three hours or driven no more than 1 mile (1.6 km).
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Wheel Replacement
Replace any wheel that is bent, cracked or badly rusted
or corroded. If wheel nuts keep coming loose, the
wheel, wheel bolts and wheel nuts should be replaced.
If the wheel leaks air, replace it (except some
aluminum wheels, which can sometimes be repaired).
See your dealer if any of these conditions exist.
Your dealer will know the kind of wheel you need.
Each new wheel should have the same load-carrying
capacity, diameter, width, offset and be mounted
the same way as the one it replaces.
If you need to replace any of your wheels, wheel bolts
or wheel nuts, replace them only with new GM
original equipment parts. This way, you will be sure to
have the right wheel, wheel bolts and wheel nuts
for your vehicle.{CAUTION:
Using the wrong replacement wheels, wheel
bolts, or wheel nuts on your vehicle can be
dangerous. It could affect the braking and
handling of your vehicle, make your tires lose
air and make you lose control. You could have
a collision in which you or others could be
injured. Always use the correct wheel, wheel
bolts and wheel nuts for replacement.
Notice:The wrong wheel can also cause problems
with bearing life, brake cooling, speedometer or
odometer calibration, headlamp aim, bumper height,
vehicle ground clearance, and tire or tire chain
clearance to the body and chassis.
SeeChanging a Flat Tire on page 5-64for more
information.
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