Lesson 3/Learning Event 2
Learning Event 2:
DESCRIBE THE TYPES, CONSTRUCTION, AND INSPECTION PROCEDURES OF
TIRES AND WHEELS
CONSTRUCTION AND TYPES OF TIRES AND TUBES
Additional cushioning and traction qualities are provided by the vehicle tires. The tire
assembly generally used on trucks consists of the tire, inner tube, and flap. The inner
tube contains the air, and the flap protects the tube in the rim and bead area.
The parts that make up the tire are the tread, breaker, cushion, plies, and bead. Each part
of the tire serves a definite purpose.
The tread is a layer of rubber on the outside of the tire. It is the part that contacts the
road and is the wearing surface. The tread is designed to reduce skids and to increase the
traction needed for driving and braking the vehicle. The tread also protects the cords
(breakers) from cuts, bruises, and moisture. Rubber extends from the tread down over
the sidewalls of the tire to protect the cords.
Breakers are layers of rubber-covered cords (strings). They are similar to plies, but the
cords are spaced farther apart. When the tire hits a bump, the breakers spread out the
shock. This prevents a lot of strain from being placed on one small section of the plies.
The breakers also prevent the tread from separating from the tire.
The cushion is soft, heat-resisting rubber. It absorbs road shocks, and it bonds (fastens)
the breakers to the plies. Cord plies have strength to resist internal pressures, to support
loads, and to absorb road shocks.
The bead is the part of the tire that secures the tire to the rim. It consists of hard rubber
molded in and around steel wire cables. The cord plies are wrapped around the bead to
secure it to the tire sidewalls.
Some tires are built for use without inner tubes. These are called tubeless tires and have
a soft rubber liner on their insides to prevent air leaks.