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(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/transaxle, 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. SeeIn ation - Tire Pressure
on page 422.
Curb Weight:This means 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.
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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
includes the Tire Identi cation 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 Your Vehicle on page 354.
GAWR FRT:Gross Axle Weight Rating for the
front axle. SeeLoading Your Vehicle on page 354.
GAWR RR:Gross Axle Weight Rating for the
rear axle. SeeLoading Your Vehicle on page 354.
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 In ation Pressure:The maximum air
pressure to which a cold tire may be in ated.
The maximum air pressure is molded onto
the sidewall.
Maximum Load Rating:The load rating for a tire
at the maximum permissible in ation 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). SeeLoading Your Vehicle
on page 354.
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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.
Passenger (P-Metric) Tire:A tire used on
passenger cars and some light duty trucks and
multipurpose vehicles.
Recommended In ation Pressure:Vehicle
manufacturer’s recommended tire in ation
pressure as shown on the tire placard. See
In ation - Tire Pressure on page 422andLoading
Your Vehicle on page 354.
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.
SeeWhen It Is Time for New Tires on page 428.
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 431.
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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 354.
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 354.
Run-Flat Tires
Your vehicle, when new, had run- at tires. There
is no spare tire, no tire changing equipment,
and no place to store a tire in the vehicle. Run- at
tires perform so well without any air that a Tire
Pressure Monitor (TPM) is used to alert you
if a tire has lost pressure.If a tire goes at, you will not need to stop on the
side of the road to change the tire. You can
just keep on driving. The shorter the distance you
drive and the slower the speed, the greater the
chance that the tire will not have to be replaced. If
you drive on a de ated run- at tire for 50 miles
(80 km) or less and at speeds of 55 mph (90 km/h)
or less, there is a good chance that the tire can
be repaired. The tire can operate effectively
with no air pressure for up to 100 miles (160 km)
at speeds up to 55 mph (90 km/h), but the tire
would then have to be replaced. When a tire
is lled with air, it provides a cushion between the
road and the wheel. Because you will not have
this cushion when driving on a de ated tire, try to
avoid potholes that could damage your wheel
and require replacement of it.
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