When inspecting tires, you should look closely at
the outer sidewall, tread area, and inner sidewall for
bulges, splits, cracks, chunking, cupping, and other
abnormal wear or damage. If problems are found
before repairing or replacing the tire, determine what
caused the failure.
Tire Impact Damage
Tire impact damage or road damage includes tears,
punctures, cuts, and other physical injuries. Depending
upon the severity of the damage, the tire must either be
repaired or replaced.
Tire Wear Patterns
Tire wear patterns can be studied to determine the
cause of abnormal tread wear. By inspecting the tread
wear, you can determine what parts should be serviced,
repaired, or replaced. Common tread wear patterns are
as follows (fig. 8-47):
FEATHERING (A) is caused by erratic
scrubbing against the surface of the road when the tire is
in need of toe-in or toe-out alignment correction.
OVERINFLATION (B) causes fast center line
wear in bias and bias belted tires. In this case, the center
of the tread has more contact with the road and wears
faster than the outer area of the tread.
UNDERINFLATION (C) causes the outer tread
areas (shoulders) of the tire to have more contact with
the road; therefore, they wear faster than the center area
of the tread.
ONE-SIDE WEAR (D) is caused by excessive
camber, which means that the tire is leaning too much to
the inside or outside. This places all the work on one
side of the tire, resulting in excessive wear.
CUPPING (E) is caused by several problems,
such as imbalanced wheels. faulty shock absorbers,
faulty ball joints. or a combination of these troubles.
Tire Inflation Problems
The correct tire inflation pressure is important to
the service life of the tire. Proper inflation is required to
ensure that the tread of the tire fully contacts the road
surface. This condition allows for even wear across the
tread, therefore. resulting in increased tire life and
improved handling and safety.
Tire overinflation causes the center area of the
tread to wear quickly. The high pressure causes the
Figure 8-47.Tread wear patterns.
body of the tire to stretch outward, pushing the center
of the tread against the road surface. This action lifts
the outer edges of the tread OFF the road. An
overinflated tire produces a rough or hard ride. It is also
more prone to impact damage.
Tire underinflation is a very common and
destructive problem. This condition wears the outer
edges of the tread (shoulders) because low pressure
allows the sidewalls of the tire to flex which builds up