WARNING: (Continued)
.Overinflated tires are more likely to be
cut, punctured, or broken by a sudden
impact—such as when you hit a pothole.
Keep tires at the recommended pressure.
.Worn, old tires can cause accidents.
If the tire's tread is badly worn, or if your
vehicle's tires have been damaged,
replace them.
Tire Sidewall Labeling
Useful information about a tire is molded into its
sidewall. The examples below show a typical
passenger car tire and a compact spare tire
sidewall.
Passenger Car Tire Example
(A) 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 for more detail.
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(B) 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.
(C) Tire Identification Number (TIN)
:The
letters and numbers following DOT code are the
Tire Identification 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) Tire Ply Material
:The type of cord and
number of plies in the sidewall and under the
tread.
(E) 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
see Uniform Tire Quality Grading
on page 6‑65.
(F) Maximum Cold Inflation Load Limit
:
Maximum load that can be carried and the
maximum pressure needed to support that load.
For information on recommended tire pressure
see Inflation - Tire Pressure
on page 6‑57and
Loading the Vehicle
on page 5‑14.
Compact Spare Tire Example
(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 flat.
See Compact Spare Tire
on page 6‑78andIf a
Tire Goes Flat
on page 6‑69.
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(B) Tire Ply Material:The type of cord and
number of plies in the sidewall and under the
tread.
(C) Tire Identification Number (TIN)
:The Tire
Identification 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 Inflation Load Limit
:
Maximum load that can be carried and the
maximum pressure needed to support that load.
See Compact Spare Tire
on page 6‑78and
Loading the Vehicle
on page 5‑14.
(E) Tire Inflation
:The temporary use tire or
compact spare tire should be inflated to 60 psi
(420 kPa). For more information on tire pressure
and inflation see Inflation - Tire Pressure
on
page 6‑57
.
(F) Tire Size
:A combination of letters and
numbers define a tire's width, height, aspect ratio,
construction type and service description. The
letter T as the first character in the tire size means
the tire is for temporary use only.
Tire Size
The following illustration shows an example of a
typical passenger car tire size.
(A) Passenger (P‐Metric) Tire:The United
States version of a metric tire sizing system. The
letter P as the first 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 70, as
shown in item C of the illustration, it would mean
that the tire's sidewall is 70% as high as it is wide.
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(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 index and speed rating of the
tire. The load index represents the load carry
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 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. See Inflation - Tire Pressure
on
page 6‑57
.
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
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includes the Tire Identification Number (TIN), an
alphanumeric designator which can also identify
the tire manufacturer, production plant, brand, and
date of production.
GVWR
:Gross Vehicle Weight Rating. See
Loading the Vehicle
on page 5‑14.
GAWR FRT
:Gross Axle Weight Rating for the
front axle. See Loading the Vehicle
on page 5‑14.
GAWR RR
:Gross Axle Weight Rating for the
rear axle. See Loading the Vehicle
on page 5‑14.
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 Inflation Pressure
:The maximum air
pressure to which a cold tire can be inflated. The
maximum air pressure is molded onto the
sidewall.
Maximum Load Rating
:The load rating for a
tire at the maximum permissible inflation 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). See Loading the Vehicle
on
page 5‑14
.
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.
6-55
Passenger (P-Metric) Tire:A tire used on
passenger cars and some light duty trucks and
multipurpose vehicles.
Recommended Inflation Pressure
:Vehicle
manufacturer's recommended tire inflation
pressure as shown on the tire placard. See
Inflation - Tire Pressure
on page 6‑57and Loading
the Vehicle
on page 5‑14.
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 6‑63.
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. See Uniform
Tire Quality Grading
on page 6‑65.
Vehicle Capacity Weight
:The number of
designated seating positions multiplied by 150 lbs
(68 kg) plus the rated cargo load. See Loading the
Vehicle
on page 5‑14.
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 inflation pressure. See “Tire and
Loading Information Label” underLoading the
Vehicle
on page 5‑14.
6-56
Inflation - Tire Pressure
Tires need the correct amount of air pressure to
operate effectively.
Notice:Do not let anyone tell you that under‐
inflation or over‐inflation is all right. It is not.
If your tires do not have enough air (under‐
inflation), you can get the following:
.Too much flexing
.Too much heat
.Tire overloading
.Premature or irregular wear
.Poor handling
.Reduced fuel economy
If your tires have too much air (over‐inflation),
you can get the following:
.Unusual wear
.Poor handling
.Rough ride
.Needless damage from road hazards A vehicle specific Tire and Loading Information
label is attached to your vehicle. This label shows
your vehicle's original equipment tires and the
correct inflation pressures for your tires when they
are cold. The recommended cold tire inflation
pressure, shown on the label, is the minimum
amount of air pressure needed to support your
vehicle's maximum load carrying capacity.
For additional information regarding how much
weight your vehicle can carry, and an example of
the Tire and Loading Information label, see
Loading the Vehicle
on page 5‑14. How you load
your vehicle affects vehicle handling and ride
comfort. Never load your vehicle with more weight
than it was designed to carry.
When to Check
Check your tires once a month or more. Do not
forget to check the compact spare tire, it should
be at 60 psi (420 kPa). For additional information
regarding the compact spare tire, see Compact
Spare Tire
on page 6‑78.
6-57
How to Check
Use a good quality pocket-type gage to check tire
pressure. You cannot tell if your tires are properly
inflated simply by looking at them. Radial tires
may look properly inflated even when they are
under‐inflated. Check the tire's inflation 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 firmly onto the valve to get a
pressure measurement. If the cold tire inflation
pressure matches the recommended pressure on
the Tire and Loading Information label, no further
adjustment is necessary. If the inflation pressure
is low, add air until you reach the recommended
amount.
If you overfill 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.
The TPMS sensors monitor the air pressure in your
vehicle's tires and transmit tire pressure readings to a
receiver located in the vehicle.
Each tire, including the spare (if provided), should be
checked monthly when cold and inflated to the inflation
pressure recommended by the vehicle manufacturer on
the vehicle placard or tire inflation pressure label. (If
your vehicle has tires of a different size than the size
indicated on the vehicle placard or tire inflation pressure
label, you should determine the proper tire inflation
pressure for those tires.)
As an added safety feature, your vehicle has been
equipped with a tire pressure monitoring system
(TPMS) that illuminates a low tire pressure telltale when
one or more of your tires is significantly under‐inflated.
Accordingly, when the low tire pressure telltale
illuminates, you should stop and check your tires as
soon as possible, and inflate them to the proper
pressure. Driving on a significantly under‐inflated tire
causes the tire to overheat and can lead to tire failure.
Under‐inflation also reduces fuel efficiency and tire
tread life, and may affect the vehicle's handling and
stopping ability.
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