(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 certified to carry. The load index
can range from 1 to 279. The speed rating is
the maximum speed a tire is certified to carry a
load. 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/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. See Inflation - 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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