Buick LeSabre 1965 Service Manual page 435

7 - 8 TROUBLE DIAGNOSIS
CHASSIS SUSPENSION
SECTION 7-B
TROUBLE DIAGNOSIS—CHASSIS SUSPENSION
CONTENTS OF SECTION 7-B
Paragraph Subject
7-4 Abnormal Tire Wear . . .
7-5 Faulty Springs, Shock
Absorbers or Ball Joints
7-4 ABNORMAL TIRE
WEAR
a. General Operating
Conditions
Assuming that there is no mis-
alignment condition to cause un-
natural wear, the life of tires
depends largely upon car oper-
ating conditions and d r i v i n g
habits.
Tires wear at a much faster rate
in some localities than in others
because of road and operating
conditipns. Some types of roads
are much more abrasive than
others. Tire wear is also depend-
ent upon the number of hills and
mountains which the car must go
up and down, the severity of
grades, the number of starts and
stops, driving speeds, the amount
of rain and snow, and prevailing
temperatures. T i r e wear in-
creases rapidly with speed, tem-
perature, and load on tire. Tires
used at low speeds, in cool cli-
mates, or with light loads will
have longer life than tires used
for high speed driving in hot cli-
mates with heavy loads.
Driving habits have a very im-
portant bearing on tire life. A
careful driver may obtain much
greater mileage from a set of
tires than would be obtained by a
severe or careless driver. Rapid
acceleration and deceleration, se-
vere application of brakes, taking
turns at excessive speed, high
speed driving, and striking curbs
or other obstructions which lead
to misalignment are d r i v i n g
habits which will shorten the life
of any tire.
Page
7-8
7-10
Paragraph Subject
7-6 Improper Steering Action . .
7-7 Car Roughness or Vibration
Page
7-11
7-12
Maintenance of proper inflation
pressure and periodic interchang-
ing 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 f r i c t i o n
caused by the flexing of the side
walls. Tire squealing on turns is
an indication of underinflation or
excessive speed on the turns. A
c o m b i n a t i o n of underinflation,
high road temperatures, and high
speed driving will quickly ruin
the best tire made.
High speed on straight highways
or expressways normally causes
more rapid wear on the rear than
on the front tires, although cup-
ping 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, to-
gether with information as to lo-
cality in which the car has been
operated w i l l usually indicate
whether abnormal wear is due
to the operating conditions de-
scribed above, or to mechanical
faults which should be corrected.
The various types of abnormal
tire wear and their causes are
described in the following sub-
paragraphs.
b. 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 com-
presses due to the low internal
air pressure. This action causes
the shoulders to take all of the
driving and braking load, result-
ing in much faster wear of shoul-
ders than of the center of tread.
See Figure 7-6, View A. For
maximum results in handling,
riding and tire life, tire inflation
pressures should never be allow-
ed to go below the specified mini-
mum pressure (par. 1-2).
Continuous high speed driving on
curves, right and left, may pro-
duce 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 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 s l o w e r speeds on
curves. Do not increase tire in-
flation pressures beyond specified
limits as this will cause center
or overinflation wear (subpar. c,
below).
c. Center or Overinflation
Tread Wear
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 the t r e a d therefore
wears away much faster than the
shoulders and, if tire is contin-
uously overinflated, may be worn
thin while the shoulders have
plenty of tread material left. See
Figure 7-4, View B.