Lesson 3/Learning Event 2
The small, red dot on the sidewall of the tire near the bead indicates the balance point.
The valve of the tire should be placed at the balance mark when the tire is installed on the
wheel to obtain the best wheel balance.
INSPECTION OF TIRES
In use, the tires of a vehicle are constantly in danger of being damaged. The tires may
run over sharp objects or strike large obstructions, such as curbs or rocks. When the tires
are being inspected during any type of service, the mechanic should be alert for all types
of cuts, punctures, and bruises. When inspecting cuts, remove the tire for repair if the cut
extends to or through any of the fabric of the plies. When there are small cuts in the tread
which do not reach the fabric, the tire need not be removed for repair. A bulge or unusual
lump on any part of the tire indicates internal damage to the plies, and the tire should be
removed for repair or replacement. The driver will normally remove sharp objects which
have entered the rubber of the tire.
On trucks equipped with dual tires in the rear, a visual check should be made to ensure
that no large rocks are lodged between the' tires. In addition to damaging the tires, rocks
can be thrown for great distances by the fast-turning wheels.
Drivers are sometimes guilty of driving a truck equipped with dual wheels when one of
the tires is flat. With two tires mounted together, a good tire supports a flat tire during
operation. However, the good tire is overloaded and is likely to blow out, or the flat tire
can slip on the rim and destroy the tube or cause further damage to the tire.
A mechanic can check dual tires by kicking the tires or striking both tires with some
object that will not bruise the tires. A flat tire on one of the dual wheels will not bounce
from the blow. This method is of no use if a tire has low pressure, but it will show if one
is completely flat.
Excess heat will damage tires. When a tire flexes too much due to low pressure, too
much heat is generated and the rubber may separate from the fabric.