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(2
09)
CHASSIS SUSPENSION
TR OUBL E
DIAGNOSIS
6-11
Figure 6-9-Underinflation Tread Wear
I
c
FEATHERED
EDGE
Figure
6-11-Toe-in
or Toe-out Tread Wear
d. Cross or Toe Tread Wear
When the front wheels
have
an excessive
amount of
either
toe-in or
toe-out,
the tires are
actually dragged
sideways
when they
travel
straight down the
road,
and a cross wear or
scraping action takes place, rapidly
wearing
away
the tread
of
tires. This cross
wear
condi-
tion will usually produce a tapered or feath-
ered edge on the ribs of the tire tread. See
figure 6-11. In most cases this can be detected
by
rubbing
the
hand across the tire tread.
If
the
tapered
or
feathered
edges
are
on the
inner sides of the ribs on one or
both
sides, it
indicates that
one
or both tires have
excessive
toe
-in,
while
the
same condition in the outer
sides of ribs indicate excessive toe-out. See
paragraph 6-30 for toe-in correction.
Cases may be encountered
wher e one
front
tire definitely indicates
toe-in wear
while the
opposite tire
indicates
t
oe-out
wear. Whenever
this
condition
is indicated
always
check
the
steering geometry or
turni ng
angles
of both
front
wheels
as
described in
paragraph 6-30.
It may
be fo
und that
the t
urning angles are
not
according to
speci fications,
so t
hat the in-
side
wheel on both turns either t
oes-in
or toes-
out too
mu
ch,
result ing in cross wear on
t
ur ns
only. Incor r ect
turning angles
are
cau sed
by
bent steering
a
rms.
faster
t
han the shoulders and, if tire is con-
tinuously overinflated, may be worn thin while
the shoulders have plenty of tread material
left. See figure 6-10.
When tire inflation pressures are maintained
within
the specified limits
(par.
6-8) the tire
will make a full contact across the entire width
of tread, thereby distributing the wear evenly
over the total surface of the entire tread
area.
r
CENTER TREAD
WEAR~
,
.,
6.
Ce nter
or Overinflation Tread W
ear
On a tire that is overinflated the center of
.
the
tread receives much more driving and
braking strain than the sides or shoulders. The
center
of tread therefore wears
away
much
Fig ure 6
-10-0verinflation
Tread Wear
Continuous high speed driving on curves,
right and left, may produce tread wear very
similar to underinflation wear and might very
easily be mistaken for such. Side thrust when
rounding turns causes wear on the sides of tire
tread. In making a turn to the left, especially
at high sp
eeds,
the outside shoulder of the
right tire and the inside shoulder of the left
tire take the side thrust and naturally receive
the most wear. The only possible correction is
to advise slower speeds on curves. Do not in-
crease tire inflation pressures beyond specified
limits as this will cause center or overinflation
wear (subpar.
c,
below).
See figu r e
6-9.
F
or
maximum
results
in han-
dling, riding and tire life, tire inflation pres-
sures should never be allowed to go below
t
he
specified minimum pressure (par. 6-8.)
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