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6-12
TROUBLE DIAGNOSIS
CHASSIS SUSPENSION
(210)
FINS O
R RAISED
PORTIONS
Figure 6-13-Cornering Tread Wear
ROU
N DED EDGE
O
F OUTSIDE
l.
SHO ULDER
,
turn is made at high speed, however, centrifu-
gal force acting on the car causes the tires to
be distorted sideways and to slip or skid on the
road surface. This produces a diagonal cross
type of wear, which in severe cases will result
in a fin or sharp edge on each rib of the tire
treads.
Cornering wear can be distinguished from
toe or camber wear by the rounding of the out-
side shoulder of the tire, and by the roughening
of the tread surface in this section denoting
severe abrasion. See figure 6-13.
No alignment or tire pressure change can be
made that will relieve cornering wear. Only
the driver can effect a cure, and that by slow-
ing down on the curves.
g. Heel and Toe Tread Wear
Heel and toe wear is a saw-tooth effect with
one end of each tread block worn more than
the other. The end which wears is that which
first grips the road when the brakes are ap-
plied. High speed driving and excessive use of
the brakes will cause this type of irregular tire
wear. This type of wear will occur on any type
of block tread design. See figure 6-14.
Heel and toe wear is not so prevalent on the
rear tires because of the propelling action which
creates a counteracting force which
wears
the
opposite end of the tread
block.
These two
stresses on the rear tires wear the tread blocks
in opposite directions and result in more even
wear, while on the f
ront
tires the braking stress
is the only one which is effective. This may be
counteracted by interchanging tires (par. 6-8).
A small amount of irregular wear, slightly
saw-toothed in appearance, at the outer seg-
ments of tires is a normal condition and is due
to the difference in circumference between the
•
Figure 6-12-Side or Camber Tread Wear
e. Side or Camber Wear
Excessive wheel camber, either positive or
negative, causes the tire to run at such an
angle to the road surface that one side of the
tread wears much more than the other. See
figure 6-12.
The amount or angle of the camber wear
will be governed by the amount of positive or
negative camber in relation to the perpendicu-
lar, and by the shape of the road surface. With
any given camber angle, tires driven on modern
flat concrete highways will show greater cam-
ber wear than when driven on the earlier type
crowned highways. Camber wear mayor may
not be smooth or uniform, depending largely
on the tire tread design.
Tire tread wear very similar in appearance
to camber wear may be caused by driving on
turns at excessive speeds. This "cornering"
tread wear
(subpar.
f, below) cannot be cor-
rected by change of camber angle.
Adjustment for specified camber is covered
in paragraph 6-30.
f.
Cornering
Trea d W
e a r
The modern independently sprung automo-
bile allows
the
driver to negotiate turns at a
much higher rate of speed with the
same
feel-
ing of safety that he had with the older type
cars. This fact is responsible for a compara-
tively new type of tread wear that can easily
be mistaken for toe or camber wear.
When a car is making a turn, the tires are
supposed to be rolling in a circle. When the
Cornering wear caused by high speed driv-
ing on curves (subpar. f, below) sometimes
has the appearance of toe wear. Care must be
used to distinguish between these two types of
wear so that the proper corrective measures
.will be used.
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