2008 PONTIAC GRAND PRIX width

Q:What is wrong with this?
A:The belt is twisted across the body.
{CAUTION:
You can be seriously injured by a twisted belt.
In a crash, you would not have the full width of
the belt to spread impact forces. If a belt is
twisted, make it straight so it can work
properly, or ask your dealer/retailer to x it.
Lap-Shoulder Belt
All seating positions in your vehicle have a
lap-shoulder belt.
Here is how to wear a lap-shoulder belt properly.
1. Adjust the seat, if the seat is adjustable, so you can
sit up straight. To see how, see “Seats” in the Index.
2. Pick up the latch plate and pull the belt across you.
Do not let it get twisted.
The lap-shoulder belt may lock if you pull the belt
across you very quickly. If this happens, let the belt
go back slightly to unlock it. Then pull the belt
across you more slowly.
If you ever pull the shoulder portion of a passenger
belt out all the way, you may engage the child
restraint locking feature. If this happens, just let the
belt go back all the way and start again.
1-22

Headlamp aiming is done with the low-beam headlamps.
The high-beam headlamps will be correctly aimed if the
low-beam headlamps are aimed properly.
To adjust the vertical aim, do the following:
1. Open the hood. SeeHood Release on page 5-11
for more information.
Find the aim dot on the lens of the low-beam lamp.
2. Locate the aim dot on the lens of the low-beam
headlamp.
3. Measure the distance from the ground to the aim
dot on the lamp. Record the distance.4. At the wall measure from the ground upward (A) to
the recorded distance from Step 3 and mark it.
5. Draw or tape a horizontal line (B) on the wall the
width of the vehicle at the height of the mark
in Step 4.
6. Turn on the low-beam headlamps and place a
piece of cardboard or equivalent in front of the
headlamp not being aimed. This should allow only
the beam of light from the headlamp being aimed to
be seen on the at surface.
Notice:Do not cover a headlamp to improve beam
cut-off when aiming. Covering a headlamp may
cause excessive heat build-up which may cause
damage to the headlamp.
5-52

Low-Prole Performance Tire (GXP)
If your vehicle has P255/45R18 size tires on the
front wheels and P225/50R18 size tires on the
rear wheels, they are classied as low-prole
performance tires. These tires are designed for very
responsive driving on wet or dry pavement. You
may also notice more road noise with low-prole
performance tires and that they tend to wear faster.
Notice:If your vehicle has low-prole tires,
they are more susceptible to damage from road
hazards or curb impact than standard prole
tires. Tire and/or wheel assembly damage
can occur when coming into contact with road
hazards like, potholes, or sharp edged
objects, or when sliding into a curb. Your
vehicle warranty does not cover this type of
damage. Keep tires set to the correct ination
pressure and, when possible avoid contact
with curbs, potholes, and other road hazards.
Tire Sidewall Labeling
Useful information about a tire is molded into its
sidewall. The examples below show a typical
passenger vehicle tire and a compact spare tire
sidewall.(A) Tire Size
:The tire size is a combination of
letters and numbers used to dene a particular
tire’s width, height, aspect ratio, construction type,
and service description. See the “Tire Size”
illustration later in this section for more detail.
(B) TPC Spec (Tire Performance Criteria
Specication)
:Original equipment tires designed
to GM’s specic tire performance criteria have a
TPC specication code molded onto the sidewall.
GM’s TPC specications meet or exceed all federal
safety guidelines.Passenger (P-Metric) Tire Example
5-63

(B) Tire Ply Material:The type of cord and
number of plies in the sidewall and under
the tread.
(C) Tire Identication Number (TIN)
:The letters
and numbers following the DOT (Department of
Transportation) code is the Tire Identication
Number (TIN). The TIN shows the manufacturer
and plant code, tire size, and date the tire was
manufactured. The TIN is molded onto both sides of
the tire, although only one side may have the date
of manufacture.
(D) Maximum Cold Ination Load Limit
:Maximum load that can be carried and the
maximum pressure needed to support that load.
(E) Tire Ination
:The temporary use tire or
compact spare tire should be inated to 60 psi
(420 kPa). For more information on tire pressure
and ination seeInflation - Tire Pressure on
page 5-69.
(F) Tire Size
:A combination of letters and
numbers dene a tire’s width, height, aspect ratio,
construction type, and service description. The
letter T as the rst character in the tire size means
the tire is for temporary use only.(G) TPC Spec (Tire Performance Criteria
Specication)
:Original equipment tires designed
to GM’s specic tire performance criteria have a
TPC specication code molded onto the sidewall.
GM’s TPC specications meet or exceed all federal
safety guidelines.
Tire Size
The following illustration shows an example of a
typical passenger vehicle tire size.
(A) Passenger (P-Metric) Tire
:The United States
version of a metric tire sizing system. The letter P
as the rst character in the tire size means a
passenger vehicle tire engineered to standards set
by the U.S. Tire and Rim Association.
5-65

(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 60, as
shown in item C of the illustration, it would mean
that the tire’s sidewall is 60 percent 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 R means radial ply construction;
the letter D means diagonal or bias ply
construction; and the letter B means belted-bias
ply construction.
(E) Rim Diameter
:Diameter of the wheel in
inches.
(F) Service Description
:These characters
represent the load range and speed rating of the
tire. The load index represents the load carry
capacity a tire is certied to carry. The load index
can range from 1 to 279. The speed rating is the
maximum speed a tire is certied to carry a load.
Speed ratings range from A to Z.
Tire Terminology and Denitions
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.
5-66

Different Size Tires and Wheels
If you add wheels or tires that are a different size than
your original equipment wheels and tires, this may affect
the way your vehicle performs, including its braking, ride
and handling characteristics, stability, and resistance to
rollover. Additionally, if your vehicle has electronic
systems such as, anti-lock brakes, traction control, and
electronic stability control, the performance of these
systems can be affected.
{CAUTION:
If you add different sized wheels, your vehicle
may not provide an acceptable level of
performance and safety if tires not
recommended for those wheels are selected.
You may increase the chance that you will
crash and suffer serious injury. Only use GM
specic wheel and tire systems developed for
your vehicle, and have them properly installed
by a GM certied technician.
SeeBuying New Tires on page 5-78andAccessories
and Modifications on page 5-3for additional information.
Uniform Tire Quality Grading
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
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-type
snow tires, space-saver, or temporary use 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.
5-80

Wheel Alignment and Tire Balance
The tires and wheels on your vehicle were aligned
and balanced carefully at the factory to give you the
longest tire life and best overall performance.
Adjustments to wheel alignment and tire balancing will
not be necessary on a regular basis. However, if you
notice unusual tire wear or your vehicle pulling to one
side or the other, 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 your wheels, wheel bolts,
wheel nuts, or Tire Pressure Monitor System (TPMS)
sensors, replace them only with new GM original
equipment parts. This way, you will be sure to have the
right wheel, wheel bolts, wheel nuts, and TPMS sensors
for your vehicle.
5-82