Maintenance
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Tire terminology and definitions
Air Pressure: The amount of air
inside the tire pressing outward on
the tire. Air pressure is expressed in
pounds per square inch (psi) or kilo-
pascal (kPa).
Accessory Weight : This means the
combined weight of optional acces-
sories. Some examples of optional
accessories are, automatic
transaxle, power seats, and air con-
ditioning.
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 kilo-
pascals (kPa) before a tire has built
up heat from driving.
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: The DOT code
includes the Tire Identification
Number (TIN), an alphanumeric des-
ignator which can also identify the
tire manufacturer, production plant,
brand and date of production.
GVWR: Gross Vehicle Weight Rating
GAWR FRT: Gross Axle Weight
Rating for the Front Axle.
GAWR RR: Gross Axle Weight
Rating for the Rear axle.
Intended Outboard Sidewall
: The
side of an asymmetrical tire, that
must always face outward when
mounted on a vehicle.
Kilopascal (kPa): The metric unit for
air pressure.
Load Index: An assigned number
ranging from 1 to 279 that corre-
sponds to the load carrying capacity
of a tire.
Maximum Inflation Pressure: The
maximum air pressure to which a
cold tire may be inflated. The maxi-
mum air pressure is molded onto the
sidewall.
Maximum Load Rating : The load
rating for a tire at the maximum per-
missible inflation pressure for that
tire.
Maximum Loaded Vehicle Weight:
The sum of curb weight; accessory
weight; vehicle capacity weight; and
production options weight.
Normal Occupant Weight: The
number of occupants a vehicle is
designed to seat multiplied by 68 kg
(150 pounds).
