Opel 1900 1973 Service Manual page 225

1873 OPEL SERVICE MANUAL
Tire Wear Irregularities
An additional cause of vibrations may sometimes be
tire wear irregularities. These can also produce noise
disturbances, and can be generally corrected by
rotating the tires, Figure 3G-6.
further, locate and correct the cause of the irregular
tire wear. See Figure 3G-7.
Use the criss-cross method of rotation of tires only
when all four tires are equally worn. In some in-
stances, it may be necessary to put the truest running
assemblies (those with the lowest tolerances) on the
front of the car.
Wheel Nut Torque end Tightening Specifications
During all wheel installations, it is important to use
the correct procedures for installing wheel nuts and
torquing them uniformly and in proper sequence.
This is important in order to avoid possible distor-
tion of the brake drum or disc, and to minimize
damage to lug and nut threads and wheel stud holes.
To assure uniform tightening of wheel lug nuts, the
following procedure is recommended:
1. Install wheel lug nuts in a criss-cross pattern
tighten just enough to seat wheel against hub. This
assures proper piloting of the wheel on its hub.
2. Tighten lug nuts uniformly to proper torque of 65
An impact wrench should not be used, as uniform
torque control cannot be maintained.
Summary of Diagnosis end Correction of Tire and
Wheel Vibration
1. Inflate all tires to recommended pressure and
road-test car with owner to define problem.
2. Spin front tire/wheel assemblies with wheel driv-
ing equipment. Rear wheels may be spun with tires
off the ground and with one wheel held at a time. The
offending tire may cause vibration that may be felt
by touching the bumper or fender. By process of
elimination, determine offending tire/wheel assem-
bly.
3. Check for tire/wheel unbalance. Balance, if neces-
sary.
4. Check each tire/wheel assembly on the car for
radial runout on the tire tread. Wheel and tire assem-
blies exceeding .050 inches may be considered as
offending assemblies. Offending tire/wheel assembly
should be deflated and the tire repositioned (indexed)
180 degrees from original location.
5. After repositioning, rebalance tire/wheel assembly
(static and dynamic preferred).
Before proceeding
6. Test drive and evaluate correction.
The following procedure should be used to determine
cause of roughness or vibration with car in operation
at various speeds:
car at center of rear axle housing.
2. With transmission in "Drive", run engine at vari-
ous car speeds to note speeds at which vibration or
roughness occurs.
3. Remove rear wheels and run engine again at the
critical speeds noted in step 2. If roughness is gone,
the condition is caused by unbalanced wheel and tire
assemblies.
4. If roughness still exists with rear wheels removed,
remove rear brake drums and repeat the running
test. Elimination of the roughness indicates out of
balance brake drums.
and
5. If roughness still exists with brake drums
removed, run engine with transmission in "Neutral".
Elimination of the roughness indicates that propeller
shaft is out of balance. Continued roughness indi-
cates an out-of- balance engine.
ABNORMAL TIRE WEAR
General Operating Conditions
Assuming that there is no misalignment condition to
cause abnormal wear, the life of tires depends largely
upon car operation conditions and driving habits.
Tires wear at a much faster rate in some localities
than in others because of road and operating condi-
tions. Some types of roads are much more abrasive
than others. Tire wear is also dependent 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, driging speeds, the amount of rain
and snow, and prevailing temperatures.
increases rapidly with speed, temperature, and load
on
with light loads will have longer life than tires used
for high-speed driving in hot climates with heavy
loads.
Driving habits have a very important hearing on tire
life. A careful driver may obtain much greater mile-
age from a set of tires than would be obtained by a
Tires used at low speeds, in cool climates, or
Tire wear