2007 PONTIAC GRAND PRIX tire type
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Loss of Control
Let us review what driving experts say about what
happens when the three control systems — brakes,
steering, and acceleration — do not have enough
friction where the tires meet the road to do what the
driver has asked.
In any emergency, do not give up. Keep trying to
steer and constantly seek an escape route or
area of less danger.
Skidding
In a skid, a driver can lose control of the vehicle.
Defensive drivers avoid most skids by taking
reasonable care suited to existing conditions, and
by not overdriving those conditions. But skids
are always possible.
The three types of skids correspond to your
vehicle’s three control systems. In the braking skid,
your wheels are not rolling. In the steering or
cornering skid, too much speed or steering in a
curve causes tires to slip and lose cornering force.
And in the acceleration skid, too much throttle
causes the driving wheels to spin.
A cornering skid is best handled by easing your
foot off the accelerator pedal.If you do not have the Enhanced Traction System
(ETS) or the Traction Control System (TCS), or
if the system is off, then an acceleration skid
is also best handled by easing your foot off the
accelerator pedal. SeeEnhanced Traction System
(ETS) on page 293orTraction Control System
(TCS) on page 292.
If your vehicle starts to slide, ease your foot off the
accelerator pedal and quickly steer the way you
want the vehicle to go. If you start steering quickly
enough, your vehicle may straighten out. Always be
ready for a second skid if it occurs.
Of course, traction is reduced when water, snow,
ice, gravel, or other material is on the road.
For safety, you will want to slow down and adjust
your driving to these conditions. It is important
to slow down on slippery surfaces because
stopping distance will be longer and vehicle control
more limited.
While driving on a surface with reduced traction, try
your best to avoid sudden steering, acceleration, or
braking, including reducing vehicle speed by
shifting to a lower gear. Any sudden changes could
cause the tires to slide. You may not realize the
surface is slippery until your vehicle is skidding.
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Page 327 of 526
Total Weight on Your Vehicle’s Tires
Be sure the vehicle’s tires are in ated to the upper
limit for cold tires. These numbers can be found
on the Tire and Loading Information label,
that is located on the driver’s side center B-pillar.
SeeLoading Your Vehicle on page 317.Be
sure not to go over the GVW limit for the vehicle,
or the GAWR, including the weight of the trailer
tongue. If a weight distribution hitch is used, make
sure not to go over the rear axle limit before
applying the weight distribution spring bars.
Hitches
It is important to have the correct hitch equipment.
Crosswinds, large trucks going by, and rough
roads are a few reasons why the correct hitch is
needed. Here are some rules to follow:
The rear bumper on the vehicle is not intended
for hitches. Do not attach rental hitches or
other bumper-type hitches to it. Use only
a frame-mounted hitch that does not attach to
the bumper.
If any holes need to be made in the body of the
vehicle to install a trailer hitch, then be sure to
seal the holes later when the hitch is removed.
If the holes are not sealed, deadly carbon
monoxide (CO) from the exhaust can get into
the vehicle. SeeEngine Exhaust on page 119.
Dirt and water can, too.
Safety Chains
Always attach chains between the vehicle and the
trailer. Cross the safety chains under the tongue of
the trailer so that the tongue will not drop to the
road if it becomes separated from the hitch.
Instructions about safety chains may be provided
by the hitch manufacturer or by the trailer
manufacturer. Follow the manufacturer’s
recommendation for attaching safety chains and do
not attach them to the bumper. Always leave just
enough slack so the rig can be turned around. And,
never allow safety chains to drag on the ground.
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Page 401 of 526
Low-Pro le 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 classi ed as low-pro le
performance tires. These tires are designed for
very responsive driving on wet or dry pavement.
You may also notice more road noise with
low-pro le performance tires and that they tend to
wear faster.
Notice:If your vehicle has low-pro le tires,
they are more susceptible to damage from road
hazards or curb impact than standard pro le
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 GM
warranty does not cover this type of damage.
Keep tires set to the correct in ation 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.
Passenger (P-Metric) Tire Example
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(A) Tire Size:The tire size is a combination of
letters and numbers used to de ne 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
Speci cation):Original equipment tires designed
to GM’s speci c tire performance criteria have
a TPC speci cation code molded onto the sidewall.
GM’s TPC speci cations meet or exceed all
federal safety guidelines.
(C) DOT (Department of Transportation):The
Department of Transportation (DOT) code
indicates that the tire is in compliance with the
U.S. Department of Transportation Motor Vehicle
Safety Standards.(D) Tire Identi cation Number (TIN):The letters
and numbers following DOT (Department of
Transportation) code is the Tire Identi cation
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.
(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 418.
(G) Maximum Cold In ation Load
Limit:Maximum load that can be carried
and the maximum pressure needed to support
that load.
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(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, see
Compact Spare Tire on page 447andIf a Tire
Goes Flat on page 422.(B) Tire Ply Material:The type of cord and
number of plies in the sidewall and under
the tread.
(C) Tire Identi cation Number (TIN):The letters
and numbers following the DOT (Department of
Transportation) code is the Tire Identi cation
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 In ation Load
Limit:Maximum load that can be carried and
the maximum pressure needed to support
that load.
(E) Tire In ation:The temporary use tire or
compact spare tire should be in ated to 60 psi
(420 kPa). For more information on tire pressure
and in ation seeIn ation - Tire Pressure on
page 408.
(F) Tire Size:A combination of letters and
numbers de ne 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.
Compact Spare Tire Example
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(G) TPC Spec (Tire Performance Criteria
Speci cation):Original equipment tires designed
to GM’s speci c tire performance criteria have
a TPC speci cation code molded onto the sidewall.
GM’s TPC speci cations 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 certi ed to carry. The load index
can range from 1 to 279. The speed rating is
the maximum speed a tire is certi ed to carry a
load. Speed ratings range from A to Z.
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How to Check
Use a good quality pocket-type gage to check tire
pressure. You cannot tell if your tires are
properly in ated simply by looking at them. Radial
tires may look properly in ated even when they
are under-in 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
in ation 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.
Re-check 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.
Tire Pressure Monitor System
The Tire Pressure Monitor System (TPMS) uses
radio and sensor technology to check tire pressure
levels. If your vehicle has this feature, sensors
are mounted onto each tire and wheel assembly,
except for the spare tire. The TPMS sensors
monitor the air pressure in your vehicle’s tires and
transmit tire pressure readings to a receiver
located in the vehicle.
When a low tire pressure condition is detected,
the TPMS will illuminate the low tire pressure
warning symbol on the instrument panel cluster,
and at the same time a warning message to check
the pressure in a speci c tire displays on the
Driver Information Center (DIC). The low
tire pressure warning light and the DIC warning
message CHECK TIRE PRESSURE come
on at each ignition cycle until the tires are in ated
to the correct in ation pressure.
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Tire Inspection and Rotation
Tire rotation is not recommended if your vehicle is
a GXP model equipped with P255/45R18 size
tires on the front wheels and P225/50R18 size tires
on the rear wheels. Different tire sizes front to
rear should not be rotated.
Tire rotation is recommended if the original
equipment tires installed on your vehicle are
of the same size and type on all four tire/wheel
positions. Original equipment tires of the
same size and type should be rotated every
5,000 to 8,000 miles (8 000 to 13 000 km).
Any time you notice unusual wear, rotate your
vehicle’s tires as soon as possible and check the
wheel alignment. Also check for damaged tires
or wheels. SeeWhen It Is Time for New Tires on
page 415andWheel Replacement on page 419
for more information.
The purpose of regular rotation is to achieve more
uniform wear for all tires on the vehicle. The
rst rotation is the most important. SeeScheduled
Maintenance on page 473for scheduled rotation
intervals.The correct rotation pattern shown here is only for
non-GXP tires.
Do not include the compact spare tire, if equipped,
in your vehicle’s tire rotation.
After the tires have been rotated, adjust the front
and rear in ation pressures as shown on the Tire
and Loading Information label, and reset the Tire
Pressure Monitor System. SeeTire Pressure
Monitor System on page 409for additional
information.
Rotation Pattern for Non-GXP Tires Only
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