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.
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 Tire 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 9-46.
Curb Weight
: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
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. SeeLoading the Vehicle
on page 8-28.
GAWR FRT
:Gross Axle Weight
Rating for the front axle. See
Loading the Vehicle on
page 8-28.
Vehicle Service and Care 9-43
2008 - Pontiac G8 Owner Manual
the alignment might need to be
checked. If you notice your vehicle
vibrating when driving on a
smooth road, the tires and wheels
might need to be rebalanced.
See your dealer/retailer for proper
diagnosis.
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/retailer if any of
these conditions exist.
Your dealer/retailer 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 the
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 the 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 (V6
Engine) on page 9-71for more
information.
Used Replacement Wheels
{CAUTION
Putting a used wheel on the
vehicle is dangerous. You
cannot know how it has been
used or how far it has been
driven. It could fail suddenly
and cause a crash. If you have
to replace a wheel, use a new
GM original equipment wheel.
Vehicle Service and Care 9-61
2008 - Pontiac G8 Owner Manual
