10-54 Vehicle Care
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 kPa (kilopascal)
or psi (pounds per square inch).
Accessory Weight
: The
combined weight of optional
accessories. Some examples
of optional accessories are
automatic transmissio n, 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 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 kPa (kilopascal)
or psi (pounds per square inch)
before a tire has built up heat
from driving. See Tire Pressure
on page 10‑56.
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 Vehicle Load Limits
on page 9‑10.
GAWR FRT
: Gross Axle Weight
Rating for the front axle. See
Vehicle Load Limits on
page 9‑10.
GAWR RR
: Gross Axle Weight
Rating for the rear axle. See
Vehicle Load Limits on
page 9‑10.
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