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394 Vehicle Care
{Warning
The brake wear warning
sound means that soon the
brakes will not work well.
That could lead to a crash.
When the brake wear
warning sound is heard,
have the vehicle serviced.
Caution
Continuing to drive with
worn-out brake linings could
result in costly brake repairs.
Properly torqued wheel nuts
are necessary to help prevent
brake pulsation. When tires
are rotated, inspect brake
linings for wear and evenly
tighten wheel nuts in the
proper sequence to torque
specifications. See Capacities
and Specifications 0480.
Brake linings should be
replaced as complete
axle sets.
Brake Squeal and
Brake Dust
Some driving conditions or
climates can cause a brake
squeal when the brakes are
first applied, clearing up
following several applies. This
does not mean something is
wrong with the brakes.
Vehicles equipped with high
performance brake systems
provide superior fade
resistance, but will produce
increased brake squeal and
brake dust on the wheels and
calipers as compared to
standard brake linings. This is
normal.
To help reduce squeal, high
performance brake pads are
treated with an anti-squeal
paste that may need to be
reapplied periodically as part
of normal vehicle maintenance.
The anti-squeal paste will
dissipate over time. Also, the
use of wheel cleaners or
power washers directly on the
brake calipers may remove the anti-squeal paste from the
brake pads. It may be
necessary to reapply the
anti-squeal paste if it is
removed during cleaning.
If brake squeal is excessive,
the anti-squeal paste should
be reapplied. The anti-squeal
paste should always be
reapplied whenever the brake
pads are removed or replaced.
See your dealer for service.
Brake Pedal Travel
See your dealer if the brake
pedal does not return to
normal height, or if there is a
rapid increase in pedal travel.
This could be a sign that brake
service may be required.
Replacing Brake System
Parts
Always replace brake system
parts with new, approved
replacement parts. If this is
not done, the brakes may not
work properly. The braking
performance can change in
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Vehicle Care 417
tires be installed on the
vehicle if frequent driving at
temperatures below
approximately 5 °C (40 °F) or
on ice or snow covered roads
is expected. See Winter Tires
0414.
Caution
High performance summer
tires have rubber
compounds that lose
flexibility and may develop
surface cracks in the tread
area at temperatures below
−7 °C (20 °F). Always store
high performance summer
tires indoors and at
temperatures above −7 °C
(20 °F) when not in use. If the
tires have been subjected to
−7 °C (20 °F) or less, let them
warm up in a heated space
to at least 5 °C (40 °F) for
24 hours or more before
being installed or driving a
vehicle on which they are
installed. Do not apply heat
(Continued)
Caution (Continued)
or blow heated air directly
on the tires. Always inspect
tires before use. See Tire
Inspection0429.
Tire Sidewall Labeling
Useful information about a
tire is molded into its
sidewall. The example
shows a typical passenger
tire sidewall.
Passenger Tire Example
(1) Tire Size:The tire size
is a combination of letters
and numbers used to
define a particular tire's
width, height, aspect ratio,
construction type, and
service description. See the
“Tire Size” illustration later
in this section.
(2) TPC Spec (Tire
Performance Criteria
Specification)
:Original
equipment tires designed
to GM's specific tire
performance criteria have a
TPC specification code
molded onto the sidewall.
GM's TPC specifications
meet or exceed all federal
safety guidelines.
(3) DOT (Department of
Transportation)
:The
Department of
Transportation (DOT) code
indicates that the tire is in
compliance with the U.S.
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Vehicle Care 419
(2) Tire Width:The 3-digit
number indicates the tire
section width in millimeters
from sidewall to sidewall.
(3) Aspect Ratio
:A 2-digit
number that indicates the
tire height-to-width
measurements. For
example, if the tire size
aspect ratio is 75, as
shown in item (3) of the
illustration, it would mean
that the tire's sidewall is
75 percent as high as it
is wide.
(4) 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.
(5) Rim Diameter
:
Diameter of the wheel in
inches. (6) Service Description
:
These characters
represent the load index
and speed rating of the
tire. The load index
represents the load
carrying capacity a tire is
certified to carry. The
speed rating is the
maximum speed a tire is
certified to carry a load.
Tire Terminology and
Definitions
Air Pressure:The amount
of air inside the tire
pressing outward on each
square inch of the tire. Air
pressure is expressed
in kPa (kilopascal) or psi
(pounds per square inch).
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 kPa
(kilopascal) or psi (pounds
per square inch) before a
tire has built up heat from
driving. See Tire Pressure
0 422.
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436 Vehicle Care
balancing are not necessary
on a regular basis. Consider an
alignment check if there is
unusual tire wear or the
vehicle is significantly pulling
to one side or the other. Some
slight pull to the left or right,
depending on the crown of the
road and/or other road
surface variations such as
troughs or ruts, is normal.
If the vehicle is vibrating when
driving on a smooth road, the
tires and wheels may need to
be rebalanced. See your
dealer 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.
Some aluminum wheels can be
repaired. See your dealer if
any of these conditions exist.
Your dealer will know the kind
of wheel that is needed.Each new wheel should have
the same load-carrying
capacity, diameter, width,
offset, and be mounted the
same way as the one it
replaces.
Replace wheels, wheel bolts,
wheel nuts, or Tire Pressure
Monitor System (TPMS)
sensors with new GM original
equipment parts.
{Warning
Using the wrong
replacement wheels, wheel
bolts, or wheel nuts can be
dangerous. It could affect
the braking and handling of
the vehicle. Tires can lose air
and cause loss of control,
resulting in a crash. Always
use the correct wheel, wheel
bolts, and wheel nuts for
replacement.
{Warning
Replacing a wheel with a
used one is dangerous. How
it has been used or how far
it has been driven may be
unknown. It could fail
suddenly and cause a crash.
When replacing wheels, use
a new GM original
equipment wheel.
Caution
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.