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 5-42.
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
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 4-16.
GAWR FRT
: Gross Axle Weight
Rating for the front axle. See
Loading the Vehicle on
page 4-16.
GAWR RR
: Gross Axle Weight
Rating for the rear axle. See
Loading the Vehicle on
page 4-16.
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.
5-40 Service and Appearance Care
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