(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 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, 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.
SeeInflation - Tire Pressure on
page 9-46.
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.
Vehicle Service and Care 9-43
ProCarManuals.com
