
(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.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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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 453.
Vehicle Capacity Weight:The number of
designated seating positions multiplied by 150 lbs
(68 kg) plus the rated cargo load. SeeLoading
Your Vehicle on page 361.
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 in ation pressure. See “Tire and
Loading Information Label” underLoading
Your Vehicle on page 361.In ation - Tire Pressure
Tires need the correct amount of air pressure to
operate effectively.
Notice:Do not let anyone tell you that
under-in ation or over-in ation is all right.
It is not. If your tires do not have enough air
(under-in ation), you can get the following:
Too much exing
Too much heat
Tire overloading
Premature or irregular wear
Poor handling
Reduced fuel economy
If your tires have too much air (over-in ation),
you can get the following:
Unusual wear
Poor handling
Rough ride
Needless damage from road hazards
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Tire Pressure Monitor System
The Tire Pressure Monitor System (TPMS) uses
radio and sensor technology to check tire pressure
levels. TPMS sensors are mounted onto each
tire and wheel assembly, except the spare
tire. TPMS sensors monitor the air pressure in
your vehicle’s tires and transmit tire pressure
readings to a receiver located in the vehicle.
The TPMS is designed to alert the driver, if a low
tire pressure condition exists. If your vehicle has the
Driver Information Center (DIC), the driver can also
check tire pressure levels using the DIC.
When a low tire pressure condition is detected,
the TPMS illuminates the low tire pressure warning
symbol located on the instrument panel cluster.
If your vehicle has the DIC feature, a message
to check the pressure in a speci c tire also
appears on the DIC display. The low tire pressure
warning symbol on the instrument panel cluster
and the CHECK TIRE PRESSURE warning
message on the DIC display appears at each
ignition cycle until the tires are in ated tothe correct in ation pressure. For additional
information and details about the DIC operation
and displays seeDIC Operation and Displays
(With DIC Buttons) on page 233orDIC Operation
and Displays (Without DIC Buttons) on page 239
andDIC Warnings and Messages on page 244.
You may notice, during cooler weather conditions,
the tire pressure monitor light, located on the
instrument panel cluster, and the CHECK TIRE
PRESSURE message appears when the vehicle
is rst started and then turn off as you start to drive
the vehicle. This could be an early indicator that
the tire pressures are getting low and need to
be in ated to the proper pressure.
Each tire, including the spare (if provided), should
be checked monthly when cold and in ated to
the in ation pressure recommended by the vehicle
manufacturer on the vehicle placard or tire
in ation pressure label. (If your vehicle has tires of
a different size than the size indicated on the
vehicle placard or tire in ation pressure label,
you should determine the proper tire in ation
pressure for those tires.)
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