Maintenance38
7G201100AAM-ECTire terminology and definitions
Air Pressure: The amount of air
inside the tire pressing outward on the
tire. Air pressure is expressed in kilo-
pascal (kPa) or pounds per square
inch (psi).
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
kilopascals (kPa) or pounds per
square inch (psi) 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).
Occupant Distribution : Designated
seating positions.
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Maintenance
Outward Facing Sidewall:The side
of a asymmetrical tire that has a par-
ticular side that faces outward when
mounted on a vehicle. The outward
facing sidewall bears white lettering
or bears manufacturer, brand, and/or
model name molding that is higher or
deeper than the same moldings on
the inner facing sidewall.
Passenger (P-Metric) Tire : A tire
used on passenger cars and some
light duty trucks and multipurpose
vehicles.
Recommended Inflation Pressure :
Vehicle manufacturer's recommend-
ed tire inflation pressure and shown
on the tire placard.
Radial Ply Tire : A pneumatic tire in
which the ply cords that extend to the
beads are laid at 90 degrees to the
centerline of the tread.
Rim: A metal support for a tire and
upon which the tire beads are seat-
ed.
Sidewall: The portion of a tire
between the tread and the bead. Speed Rating: An alphanumeric
code assigned to a tire indicating the
maximum speed at which a tire can
operate.
Traction: The friction between the
tire and the road surface. The
amount of grip provided.
Tread: The portion of a tire that
comes into contact with the road.
Treadwear Indicators: Narrow
bands, sometimes called "wear
bars," that show across the tread of a
tire when only 2/32 inch of tread
remains.
UTQGS: Uniform Tire Quality
Grading Standards, a tire information
system that provides consumers with
ratings for a tire's traction, tempera-
ture and treadwear. Ratings are
determined by tire manufacturers
using government testing proce-
dures. The ratings are molded into
the sidewall of the tire.
Vehicle Capacity Weight
: The num-
ber of designated seating positions
multiplied by 68 kg (150 lbs.) plus the
rated cargo and luggage load. Vehicle Maximum Load on the
Tire: Load on an individual tire due to
curb and accessory weight plus
maximum occupant and cargo
weight.
Vehicle Normal Load on the Tire
:
Load on an individual tire that is
determined by distributing to each
axle its share of the curb weight,
accessory weight, and normal occu-
pant weight and driving by 2.
Vehicle Placard: A label permanent-
ly attached to a vehicle showing the
original equipment tire size and rec-
ommended inflation pressure.
