Cadillac 60 Series 1963 Shop Manual page 32

CHASSIS SUSPENSION
4-9
It is recommended that tires, including the
spare, be checked at least once a month, and
that proper tire pressures be maintained. Higher
inflation pressure than recommended will cause:
1. A harder riding car.
2. A tire more susceptible to various types
of bruises.
3. Tire chatter, resulting in uneven wear.
4. Excessive wear at center of tire tread.
5. Poor steering returnability.
Inflation pressures lower than recommended
will result in:
1. Higher gasoline consumption.
2. Rapid and uneven wear toward edges of tire
tread.
3. A tire more susceptible to rim bruises and
various types of ply and tread separation.
4. Increased cord fatigue or broken tire cords.
5. Hard steering.
6. High tire temperatures.
7. Car roll on sharp curves.
8. Tire squeal on curves.
Tire pressure should always be checked when
tires are cold, never after a high speed trip.
Heat developed from fast driving or from hot
pavement increases pressures, which decrease
again when tires cool.
After checking tires, the valve stem caps should
be reinstalled. These caps are essential in keep-
ing dirt out of the valves and in reducing the
possibility of slow leaks.
d. Tire Rotation
Under normal driving conditions, periodic tire
rotation is not necessary. If abnormal tire wear
should be discovered, however, the condition
causing the problem should be determined im-
mediately and corrected. Tire rotation may be a
part of this correction.
Under some hard driving conditions, it may
still be desirable to rotate the tires regularly.
When necessary, tires should be rotated according
to the pattern shown in Fig. 4-11.
Right Front
Left Front
Left Rear
Fig. 4-1 1 Tire Rotation
e. Tire Noise Complaints
Complaints of axle noise are frequently caused
by tires rather than by differential gears or
bearings.
To determine whether tires are causing the
noise, drive the car at various speeds and note
the effect of part throttle, sudden acceleration,
and deceleration on noise level. Axle and exhaust
noise show definite variations under these condi-
tions, while tire noise will remain constant.
Tire noise may be further checked by driving
the car over smooth pavement with the tires at
normal pressure and again over the same stretch
of road when the tires have been inflated to 50
pounds pressure. If the noise for which the test
is being made is caused by tires, it will be
noticeably decreased when the tire pressure is
increased, whereas rear axle or bearing noise
should show no change in volume.
Thump is a noise caused when the tire moves
over irregularities in the road or the irregular-
ities of a tire moving over a smooth road. It is
a periodic vibration which may be heard with
varying loudness inside the car.
A noisy or thumping tire usually may be
singled out by inflating all tires to 50 pounds
pressure and then driving the car. Deflate the
tires, one at a time, to normal pressure. When
the noise or thump appears, the tire just deflated
is the faulty tire.
f. Tire arid Wheel Runout and Eccentricity
Excessive radial or lateral runout of a wheel
and tire together can cause tire roughness, tire
wear, and out of balance feel. To minimize these
effects, tire and wheel runout should be checked
and corrected as necessary. Proceed as follows:
When measuring runout on tires, check them
as soon as possible after car has been driven,