(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.
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.
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Federal Communications
Commission (FCC) and Industry
and Science Canada
The Tire Pressure Monitor System (TPMS) operates
on a radio frequency and complies with Part 15 of
the FCC Rules. Operation is subject to the following
two conditions:
1. This device may not cause harmful interference.
2. This device must accept any interference received,
including interference that may cause undesired
operation.
The TPMS operates on a radio frequency and complies
with RSS-210 of Industry and Science Canada.
Operation is subject to the following two conditions:
1. This device may not cause interference.
2. This device must accept any interference received,
including interference that may cause undesired
operation of the device.
Changes or modi cations to this system by other than
an authorized service facility could void authorization to
use this equipment.
Tire Pressure Monitor Operation
Your vehicle may have a Tire Pressure Monitor System
(TPMS) designed to warn the driver when a low tire
pressure condition exists. TPMS sensors are mounted
onto each tire and wheel assembly, excluding the spare
tire and wheel assembly. The TPMS sensors monitor
the air pressure in the vehicle’s tires and transmits
the tire pressure readings to a receiver located in the
vehicle.
When a low tire pressure
condition is detected, the
TPMS illuminates the low
tire pressure warning light
located on the instrument
panel cluster.
At the same time a message to check the pressure in
a speci c tire appears on the Driver Information Center
(DIC) display. The low tire pressure warning light and the
DIC warning message come on at each ignition cycle
until the tires are in ated to the correct in ation pressure.
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One or more TPMS sensors are missing or
damaged. The DIC message and the TPMS
malfunction light should go off when the TPMS
sensors are installed and the sensor matching
process is performed successfully. See your dealer/
retailer for service.
Replacement tires or wheels do not match your
vehicle’s original equipment tires or wheels. Tires
and wheels other than those recommended for your
vehicle could prevent the TPMS from functioning
properly. SeeBuying New Tires on page 5-64.
Operating electronic devices or being near facilities
using radio wave frequencies similar to the TPMS
could cause the TPMS sensors to malfunction.
If the TPMS is not functioning it cannot detect or
signal a low tire condition. See your dealer/retailer for
service if the TPMS malfunction light and DIC message
comes on and stays on.
TPMS Sensor Matching Process
Each TPMS sensor has a unique identi cation code. Any
time you rotate your vehicle’s tires or replace one or more
of the TPMS sensors, the identi cation codes will need to
be matched to the new tire/wheel position. The sensors
are matched to the tire/wheel positions in the following
order: driver side front tire, passenger side front tire,
passenger side rear tire, and driver side rear tire using
a TPMS diagnostic tool. See your dealer/retailer for
service.
The TPMS sensors can also be matched to each
tire/wheel position by increasing or decreasing the
tire’s air pressure. If increasing the tire’s air pressure,
do not exceed the maximum in ation pressure indicated
on the tire’s sidewall.
To decrease air-pressure out of a tire you can use the
pointed end of the valve cap, a pencil-style air pressure
gage, or a key.
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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.
Treadwear
The treadwear grade is a comparative rating
based on the wear rate of the tire when tested
under controlled conditions on a speci ed
government test course. For example, a tire
graded 150 would wear one and a half (1.5) times
as well on the government course as a tire
graded 100. The relative performance of tires
depends upon the actual conditions of their use,
however, and may depart signi cantly from the
norm due to variations in driving habits, service
practices, and differences in road characteristics
and climate.
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