1948-1952 Shop Service Manual - - Hudson-Essex-Terraplane Club

16 - 2 WHEELS AND TIRES
Due to irregularities in tread wear, caused b y sudden
brake applications, misalignment, low inflation pressure, or
tube and casing repairs, a casing and tube can lose its original
balance.
If the action of the front wheels cause a disturbance at the
steering wheel, the first items to check are air pressure and
the balance of the tire and wheel.
STATIC OR STILL BALANCE IS THE EQUAL
DISTRIBUTION OF THE WEIGHT OF THE WHEEL
AND TIRE ASSEMBLY ABOUT the axis of rotation in
such a manner that it has no tendency to rotate by itself
regardless of the position of the wheel and tire.
Static unbalance of a wheel causes a hopping or pounding
action (up and down) which leads to road tramp, high speed
shimmy and excessive tire wear.
Wheels may be statically balanced on the steering spindle
of the car, although the use of an accredited wheel balancing
fixture will facilitate the operation.
NOTE: If wheels are checked on steering spindle, brakes
must be fully released so that they do not drag and impede
free rotation of the wheel.
Static unbalance of a tire and wheel causes the heavy
portion (3) to go to the bottom as in Figure 1 and to obtain
a true static balance, weights will have to be added on the
rim opposite the heavy portion that went to the bottom.
Gradually move the weight apart, equal distances from
starting point until wheel is in balance.
NOTE: The wheel is in balance when it will stand in any
position without rotating of its own accord.
To balance the wheel and tire assembly a piece of putty
may be used instead of fastening the regular weights onto
the rim. The quantity of putty may be added to or reduced
until the static balance is obtained, as in Figure 1.
The putty can then be weighed and balanced weight or
weights attached permanently to the rim to correspond to
the weight of the putty. The sum of the weights of section
(1) and (2) is equal to the sum of the weights of section (3)
and (4), Figure 1. The weight, therefore, is equally distributed
about the axis of rotation. The weight at (2) being
balanced by the weight at (3). However this wheel is not in
dynamic balance because section (1), Figure 1 is lighter
then section (2) and section (4) is lighter than section (3).
NOTE: Dynamic or running balance requires a wheel to
be first in static balance and to also run smoothly at all
speeds on an axis that passes through the center line of
the wheel and tire and is perpendicular to the axis of
rotation.
NOTE: The wheel assembly must be clean and free of all
dirt, weights, etc. The tire must be in good condition;
properly mounted with the balance mark on the tire lined
up with the valve stem in the tube. Bent wheels must be
replaced or straightened before being balanced. Tire
valve caps must be in place.
The wheel and tire is in static balance as shown in Figure
1, however, with reference to the center line, section (1) is
lighter than section (2), also section (3) is lighter than
section (4).
NOTE: Special shop equipment is required to determine
the amount it is out of balance and where correct weight
should be added without disturbing its static balance.
This wheel when started spinning, will cause a center line
through the weights at (2) and (3) to attempt to get at right
angles to the rotation axis, Figure 2, which exerts a force
on the wheel to try to obtain a new center line and thus
change the axis of rotation. The wheel in spinning, therefore,
tries to equalize the weight at (2) and (3) by moving
the center line first in one direction and then in another,
causing the wheel to try to rock first in one direction and
heel