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(C) Aspect Ratio: A two-digit
number that indicates the tire
height-to-width measurements.
For example, if the tire size
aspect ratio is 75, as shown
in item C of the light truck
(LT-Metric) tire illustration,
it would mean that the tire’s
sidewall is 75 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
:
The service description indicates
the load range and speed
rating of a tire. The load index
can range from 1 to 279. Speed
ratings range from A to Z.
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 5-51.
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.
5-48 Service and Appearance Care