2004 GMC SIERRA Owner's Manual

(A) Light Truck (LT-Metric) Tire:The United States
version of a metric tire sizing system. The letter ªLTº as
the ®rst two characters in the tire size means a light
truck tire engineered to standards set by the U. S. Tire
and Rim Association.
(B) Tire Width:The three-digit number indicates the
tire section width in millimeters from sidewall to sidewall.
(C) Aspect Ratio:A two-digit number that indicates
the tire height-to-width measurements. For example, if
the tire size aspect ratio is ª75,º as shown in item ªCº of
the illustration, it would mean that the tire's sidewall is
75% as high as it is wide.(D) Construction Code:A letter code is used to
indicate the type of ply construction in the tire. The letter
ªRº means radial ply construction; the letter ªDº means
diagonal or bias ply construction; and the letter ªBº
means belted-bias ply construction.
(E) Rim Diameter:Diameter of the wheel in inches.
(F) Service Description:The service description
indicates the load range and speed rating of a tire. The
load index can range from 1 to 279. Speed ratings
range from ªAº to ªZº. The light truck tire size example
above shows dual or single tire con®gurations.Tire Terminology and De®nitions
Air Pressure:The amount of air inside the tire pressing
outward on each square inch of the tire. Air pressure
is expressed in pounds per square inch (psi) or
kilopascal (kPa).
Accessory Weight:This means the combined weight
of optional accessories. Some examples of optional
accessories are, automatic transmission, power steering,
power brakes, power windows, power seats, and air
conditioning.
Aspect Ratio:The relationship of a tire's height to its
width. Light Truck (LT-Metric) Tire
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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. See
In¯ation - Tire Pressure on page 5-84.
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 motor vehicle safety
standards. The DOT code includes the Tire Identi®cation
Number (TIN), an alphanumeric designator which can
also identify the tire manufacturer, production plant,
brand and date of production.
GVWR:Gross Vehicle Weight Rating, see
Loading
Your Vehicle on page 4-57.GAWR FRT:Gross Axle Weight Rating for the front
axle, see
Loading Your Vehicle on page 4-57.
GAWR RR:Gross Axle Weight Rating for the rear axle,
see
Loading Your Vehicle on page 4-57.
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.
There are 6.9 kPa's to one psi.
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 in¯ated. The
maximum air pressure is molded onto the sidewall.
Maximum Load Rating:The load rating for a tire at the
maximum permissible in¯ation pressure for that tire.
Maximum Loaded Vehicle Weight:The sum of curb
weight; accessory weight; vehicle capacity weight;
and production options weight.
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Normal Occupant Weight:The number of occupants a
vehicle is designed to seat multiplied by 150 pounds
(68 kg). See
Loading Your Vehicle on page 4-57.
Occupant Distribution:Designated seating positions.
Outward Facing Sidewall:The side of a 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 in¯ation pressure and
shown on the tire placard. See
In¯ation - Tire Pressure
on page 5-84andLoading Your Vehicle on page 4-57.
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 ªwear bars,º that show across the tread of a tire
when only 2/32 inch of tread remains. See
When It
Is Time for New Tires on page 5-88.
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. See
Uniform Tire Quality
Grading on page 5-90.
5-83

Vehicle Capacity Weight:The number of designated
seating positions multiplied by 150 lbs. (68 kg) plus
the rated cargo load. See
Loading Your Vehicle
on page 4-57.
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 original equipment tire size
and recommended in¯ation pressure. See
Loading Your
Vehicle on page 4-57.
In¯ation - Tire Pressure
The tire and loading information label, shows the correct
in¯ation pressures for your tires when they're cold.
ªColdº means your vehicle has been sitting for at least
three hours or driven no more than 1 mile (1.6 km). See
Loading Your Vehicle on page 4-57, for the location
of your vehicle's tire and loading information label.
Notice:Don't let anyone tell you that underin¯ation
or overin¯ation is all right. It's not. If your tires
don't have enough air (underin¯ation), you can get
the following:
·Too much ¯exing
·Too much heat
·Tire overloading
·Bad wear
·Bad handling
·Bad fuel economy
If your tires have too much air (overin¯ation), you
can get the following:
·Unusual wear
·Bad handling
·Rough ride
·Needless damage from road hazards
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When to Check
Check your tires once a month or more.
Also, check the tire pressure of the spare tire.
How to Check
Use a good quality pocket-type gage to check tire
pressure. You can't tell if your tires are properly in¯ated
simply by looking at them. Radial tires may look
properly in¯ated even when they're underin¯ated. Check
the tire's in¯ation 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).
Remove the valve cap from the tire valve stem. Press
the tire gage ®rmly onto the valve to get a pressure
measurement. If the cold tire in¯ation pressure matches
the recommended pressure on the tire and loading
information label, no further adjustment is necessary.
If the pressure is low, add air until you reach the
recommended amount.
If you over®ll the tire, release air by pushing on the
metal stem in the center of the tire valve. Recheck the
tire pressure with the tire gage.
Be sure to put the valve caps back on the valve stems.
They help prevent leaks by keeping out dirt and
moisture.
Dual Tire Operation
When the vehicle is new, or whenever a wheel, wheel
bolt or wheel nut is replaced, check the wheel nut torque
after 100, 1,000 and 6,000 miles (160, 1 600 and
10 000 km) of driving. For proper torque and wheel nut
tightening information, see ªRemoving the Flat Tire
and Installing the Spare Tireº in the index.
The outer tire on a dual wheel setup generally wears
faster than the inner tire. Your tires will wear more
evenly and last longer if you rotate the tires periodically.
See ªTire Inspection and Rotationº earlier in this
section. Also see ªScheduled Maintenance Servicesº in
the Index for scheduled rotation intervals
{CAUTION:
If you operate your vehicle with a tire that is
badly underin¯ated, the tire can overheat. An
overheated tire can lose air suddenly or catch
®re. You or others could be injured. Be sure all
tires (including the spare) are properly in¯ated.
See ªTiresº and ªIn¯ation ± Tire Pressureº in the Index
for more information on proper tire in¯ation.
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Tire Inspection and Rotation
Tires should be rotated every 5,000 to 8,000 miles
(8 000 to 13 000 km).
Any time you notice unusual wear, rotate your tires as
soon as possible and check wheel alignment. Also
check for damaged tires or wheels. See
When It Is Time
for New Tires on page 5-88andWheel Replacement
on page 5-92for more information.
Make sure the spare tire is stored securely. Push, pull,
and then try to rotate or turn the tire. If it moves,
use the wheel wrench/hoist shaft to tighten the cable.
See
Changing a Flat Tire on page 5-96.
If your vehicle has dual rear wheels, also see
Dual Tire
Operation on page 5-85.
The purpose of regular rotation is to achieve more
uniform wear for all tires on the vehicle. The ®rst rotation
is the most important. See
Scheduled Maintenance
on page 6-4, for scheduled rotation intervals.If your vehicle has single rear wheels and the tread
design for your front tires is the same as your rear tires,
use the rotation pattern shown here when rotating
your tires.
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If your vehicle has dual rear wheels and the tread
design for your front tires is the same as your rear tires,
always use one of the correct rotation patterns shown
here when rotating your tires.
If your vehicle has dual rear wheels and the tread design
for the front tires is different from the dual rear tires,
always use the correct rotation pattern shown here when
rotating your tires. The dual tires are rotated as a pair,
and the inside rear tires became the outside rear tires.
When you install dual wheels, be sure the vent holes in
the inner and outer wheels on each side are lined up.After the tires have been rotated, adjust the front and
rear in¯ation pressures as shown on the
Certi®cation/Tire label or Tire and Loading Information
label. See
Loading Your Vehicle on page 4-57.
Make certain that all wheel nuts are properly tightened.
See ªWheel Nut Torqueº under
Capacities and
Speci®cations on page 5-134.
{CAUTION:
Rust or dirt on a wheel, or on the parts to
which it is fastened, can make wheel nuts
become loose after a time. The wheel could
come off and cause an accident. When you
change a wheel, remove any rust or dirt from
places where the wheel attaches to the vehicle.
In an emergency, you can use a cloth or a
paper towel to do this; but be sure to use a
scraper or wire brush later, if you need to, to
get all the rust or dirt off. See ªChanging a Flat
Tireº in the Index.
5-87

When It Is Time for New Tires
One way to tell when it's
time for new tires is to
check the treadwear
indicators, which will
appear when your tires
have only 1/16 inch
(1.6 mm) or less of tread
remaining. Some
commercial truck tires may
not have treadwear
indicators.You need a new tire if any of the following statements
are true:·You can see the indicators at three or more places
around the tire.
·You can see cord or fabric showing through the
tire's rubber.
·The tread or sidewall is cracked, cut or snagged
deep enough to show cord or fabric.
·The tire has a bump, bulge or split.
·The tire has a puncture, cut or other damage that
can't be repaired well because of the size or
location of the damage.
5-88