5-28 SERVICE AND APPEARANCE CARE
78J00-03E
C. Aspect Ratio:
A two-digit number that indicates the
tire height-to-width measurements.
For example, if the tire size aspect
ratio is 60, as shown in item C of the
illustration, it would mean that the
tire’s sidewall is 60 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:
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 max-
imum speed a tire is certified to carry
a load. Speed ratings range from A to
Z.
Tire Terminology and DefinitionsAir 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 trans-
mission/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, mea-
sured in pounds per square inch (psi) orkilopascals (kPa) before a tire has built up
heat from driving. Refer to “Inflation – Tire
Pressure” in this section.
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.
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 manufac-
turer, production plant, brand, and date of
production.
GVWR:
Gross Vehicle Weight Rating. Refer to
“Loading Your Vehicle” in “Your Driving,
the Road, and Your Vehicle” in the “Driving
Your Vehicle” section.
GAWR FRT:
Gross Axle Weight Rating for the front
axle. Refer to “Loading Your Vehicle” in
“Your Driving, the Road, and Your Vehicle”
in the “Driving Your Vehicle” section.
GAWR RR:
Gross Axle Weight Rating for the rear axle.
Refer to “Loading Your Vehicle” in “Your
