36.
60 1973 OPEL SERVICE MANUAL
severe or careless driver. Rapid acceleration and de-
celeration, severe application of brakes, taking turns
at excessive speed, high-speed driving, and striking
curbs or other obstructions which lead to misalign-
ment are driving habits which will shorten the life of
any tire.
hiaintenance of proper inflation pressure and peri-
odic interchanging of tires to equalize wear are
within the control of the driver. Underinflation
raises the internal temperature of a tire greatly due
to the continual friction caused by the flexing of the
side walls. Tire squealing on turns is an indication of
underinflation or excessive speed on the turns. A
combination of underinflation, high road tempera-
tures, and high-speed driving will quickly ruin the
best tire made.
High speed on straight highways or expressways nor-
mally causes more rapid wear on the rear than on the
front tires, although cupping of front tires can result
if the tires are not periodically switched from wheel
to wheel. Driving turns and curves at too high a rate
of speed causes the front tires to wear much faster
than the rear tires.
An inspection of the tires, together with information
as to locality in which the car has been operated will
usually indicate whether abnormal wear is due to the
operating conditions described above or to mechani-
cal faults which should be corrected.
The various types of
abnormal
tire wear and their
causes are described in the following paragraphs.
Shoulder or Underinflation Tread Wear
When a tire is underinflated, the side walls and
shoulders of the tread carry the load, while the center
of tread folds in or compresses due to the low inter-
nal air pressure. This action causes the shoulders to
take all of the driving and braking load, resulting in
much faster wear of shoulders than of the center of
tread. See Figure 3G-7. For maximum results in han-
dling, riding and tire life, tire inflation pressures
should never be allowed to go below the specified
minimum pressure.
Continuous high-speed driving on curves, right and
left, may produce tread wear very similar to
underin-
flation 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 speeds, 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 increase tire inflation pres-
sures beyond specified limits, as this will cause center
or over-inflation wear. See paragraph below.
Canter or Overinflation Tread 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
3G-7.
When tire inflation pressures are maintained within
the specified limits, the tire will make a full contact
across the entire width of tread, thereby distributing
the wear evenly over the total surface of the tread
area.
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 cross wear or scraping action takes place rapidly
wearing away the tread of tires. This cross wear con-
dition will usually produce a tapered or feathered
edge on the ribs of the tire tread. See Figure
3G-7.
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 of both sides, it indicates that
one or both tires have excessive toe-in, while the
same condition in the outer sides of ribs indicates
excessive toe-out. Usually, excessive toe-in causes
excessive tire wear on the outer edge of the
right
front tire and toe-out
causes
tire wear on the inner
edge of the left front tire. See Section 3C for toe-in
correction.
Cornering wear caused by high-speed driving on
curves (see following paragraph) sometimes has the
appearance of toe wear. Care must be used to distin-
guish between these two types of wear so that the
proper corrective measures will be used.
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
3G-7.
The amount or angle of the camber wear will be
governed by the amount of positive or negative cam-
ber. Tire tread wear very similar in appearance to
camber wear may be caused by driving on turns at
excessive speeds. This “cornering” tread wear (see
paragraph below) cannot be corrected by change of
camber angle.
Adjustments for specified camber are covered in Sec-
tion 3C.
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