Tire Designations; Tire Terminology And Definitions - GMC Sierra Owner's Manual

Tire Designations

Tire Size
The examples show a typical light truck
tire size.
Light Truck (LT-Metric) Tire
(1) Light Truck (LT-Metric) Tire
United States version of a metric tire
sizing system. The letters LT as the first
two characters in the tire size mean a
light truck tire engineered to standards
set by the U.S. Tire and Rim
Association.
(2) Tire Width The 3-digit number
:
indicates the tire section width in
millimeters from sidewall to sidewall.
(3) Aspect Ratio
indicates the tire height-to-width
measurements. For example, if the tire
size aspect ratio is 75, as shown in item
3 of the light truck (LT-Metric) tire
illustration, it would mean that the
tire's sidewall is 75 percent as high as it
is wide.
(4) Construction Code
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
The
:
construction.
(5) Rim Diameter
wheel in inches.
(6) Load Range
(7) Service Description
description indicates the load index and
speed rating of a tire. If two numbers
are given as in the example, 120/116,
then this represents the load index for
single versus dual wheel usage (single/
dual). The speed rating is the maximum
speed a tire is certified to carry a load.
A 2-digit number that
:
A letter code is
:
Diameter of the
:
Load Range.
:
The service
:
Vehicle Care

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 kPa (kilopascal) or psi
(pounds per square inch).
Accessory Weight The combined
:
weight of optional accessories. Some
examples of optional accessories are
automatic transmission, 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
:
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.
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