2008 PONTIAC G8 Owners Manual

(E) Tire Ply Material:The type
of cord and number of plies
in the sidewall and under
the tread.
(F) Uniform Tire Quality
Grading (UTQG)
:Tire
manufacturers are required to
grade tires based on three
performance factors: treadwear,
traction, and temperature
resistance. For more information
seeUniform Tire Quality
Grading on page 9-59.
(G) Maximum Cold Ination
Load Limit
:Maximum load that
can be carried and the
maximum pressure needed to
support that load.(A) Temporary Use Only:The
compact spare tire or temporary
use tire has a tread life of
approximately 3,000 miles
(5 000 km) and should not be
driven at speeds over 65 mph
(105 km/h). The compact
spare tire is for emergency use
when a regular road tire has
lost air and gone at. If
your vehicle has a compact
spare tire. SeeCompact Spare
Tire on page 9-79andIf a
Tire Goes Flat on page 9-62.(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.
Compact Spare Tire Example
Vehicle Service and Care 9-41
2008 - Pontiac G8 Owner Manual

(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 see
Inflation - Tire Pressure on
page 9-46.
(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.
(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
AtoZ.
9-42 Vehicle Service and Care
2008 - Pontiac G8 Owner Manual

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.
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
Identication 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

GAWR RR:Gross Axle Weight
Rating for the rear axle. See
Loading the Vehicle on
page 8-28.
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 Ination
Pressure
:The maximum air
pressure to which a cold tire can
be inated. The maximum air
pressure is molded onto the
sidewall.
Maximum Load Rating
:The
load rating for a tire at the
maximum permissible ination
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
the Vehicle on page 8-28.
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 Ination
Pressure
:Vehicle
manufacturer’s recommended
tire ination pressure as
shown on the tire placard. See
Inflation - Tire Pressure on
page 9-46andLoading
the Vehicle on page 8-28.
9-44 Vehicle Service and Care
2008 - Pontiac G8 Owner Manual

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. See
When It Is Time for New Tires on
page 9-56.
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 9-59.
Vehicle Capacity Weight
:The
number of designated seating
positions multiplied by 150 lbs
(68 kg) plus the rated cargo load.
SeeLoading the Vehicle on
page 8-28.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 ination pressure.
See “Tire and Loading
Information Label” under
Loading the Vehicle on
page 8-28.
Vehicle Service and Care 9-45
2008 - Pontiac G8 Owner Manual

Ination - Tire Pressure
Tires need the correct amount of
air pressure to operate
effectively.
Notice:Do not let anyone tell
you that under-ination or
over-ination is all right. It is
not. If your tires do not have
enough air (under-ination),
you can get the following:
Too much exing
Too much heat
Tire overloading
Premature or irregular wear
Poor handling
Reduced fuel economyIf your tires have too much air
(over-ination), you can get
the following:
Unusual wear
Poor handling
Rough ride
Needless damage from road
hazards
A vehicle specic Tire and
Loading Information label is
attached to the vehicle’s center
pillar, below the driver’s door
latch. This label lists the
vehicle’s original equipment tires
and the recommended cold
tire ination pressure for the tires
when they are cold. The
recommended cold tire ination
pressure, shown on the label,is the minimum amount of air
pressure needed to support your
vehicle’s maximum load
carrying capacity. For more
information regarding how much
weight your vehicle can carry,
seeLoading the Vehicle on
page 8-28.
How you load your vehicle
affects vehicle handling and ride
comfort. When driving with
less than the maximum load
capacity allowed for your vehicle,
you can set tire ination
pressure to the recommended
amounts shown in the following
chart. Never load your vehicle
with more weight than it
was designed to carry.
9-46 Vehicle Service and Care
2008 - Pontiac G8 Owner Manual

Tire SizeRecommended Cold Tire InationOccupant and Cargo Weight:
573 lbs (260 kg) or Less Occupant and Cargo Weight:
Up to 917 lbs (416 kg)
(Vehicle Capacity Weight)
Front Tires Rear Tires Front Tires Rear Tires
P245/45R18 96V 33 psi (230 kPa) 33 psi (230 kPa) 36 psi (250 kPa) 39 psi (270 kPa) 245/45R18 96V 36 psi (250 kPa) 36 psi (250 kPa) 36 psi (250 kPa) 39 psi (270 kPa)
245/40R19 94W 36 psi (250 kPa) 36 psi (250 kPa
)36 psi (250 kPa) 39 psi (270 kPa)
T155/80R17 111M (Compact Spare) 60 psi (420 kPa) 60 psi (420 kPa) 60 psi (420 kPa) 60 psi (420 kPa)
When to Check
Check your tires once a month
or more.
Do not forget the compact spare
tire, if your vehicle has one. It
should be at 60 psi (420 kPa).
For more information about
the vehicle’s compact spare tire,
see Compact Spare Tire on
page 9-79 . How to Check
Use a good quality pocket-type
gage to check tire pressure.
You can’t tell if your tires
are properly inated simply by
looking at them. Radial tires may
look properly inated even
when they’re underinated.
Check the tire’s ination
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 ination pressure
matches the recommended
pressure on the Tire and
Loading Information label, no
further adjustment is necessary.
If the ination pressure is
low, add air until you reach the
recommended amount.
Vehicle Service and Care 9-47
2008 - Pontiac G8 Owner Manual

If you overll 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.High-Speed Operation
{CAUTION
Driving at high speeds,
100 mph (160 km/h) or higher,
puts an additional strain on
tires. Sustained high-speed
driving causes excessive heat
build up and can cause sudden
tire failure. You could have a
crash and you or others could
be killed. Some high-speed
rated tires require ination
pressure adjustment for high
speed operation. When speed
limits and road conditions are
such that a vehicle can be
driven at high speeds, make
sure the tires are rated for high
speed operation, in excellent
condition, and set to the
correct cold tire ination
pressure for the vehicle load.Vehicles with P245/45R18 96V,
245/45R18 96V, or 245/40R19 94W
size tires, require ination pressure
adjustment when driving the
vehicle at speeds of 100 mph
(160 km/h) or higher. Use the
following chart to determine the cold
tire ination pressure when
operating the vehicle under
high-speed conditions.
9-48 Vehicle Service and Care
2008 - Pontiac G8 Owner Manual