12-94170-01
If weight is not equally distributed around the wheel, unbalance centrifugal force by the wheel rotation
produces vibration. As the centrifugal force is produced proportional to the square of the rotating
speed, the wheel weight should be balanced even at high speed. There are two types of the tire and
wheel balancing: static and dynamic. Abnormal vibration may also occur due to unbalanced rigidity or
size of tires.
1) Static Balance
When the free rotation of the wheel is
allowed, the heavier part is stopped on the
bottom if the wheel weight is unbalanced
and this is called "Static Unbalance". Also,
the state at which tire's stop position is not
same is called "Static Balance" when the
wheel is rotated again. If the part A is heavie
r
as shown in the figure 1, add the balance
weight of a weight corresponding to
unbalanced weight from B to A to maintain
the static balance. If the static balance is not
maintained, tramping, up and down vibration
of the wheels, occurs.
2) Dynamic Balance
The static unbalance of the wheel creates
the vibration in the vertical direction, but
the dynamic unbalance creates the
vibration in the lateral direction. As shown
in the figure 2 (a), if two parts, (2) and (3),
are heavier when the wheels are under the
static balance condition, dynamic
unbalance is created, resulting in shimmy,
left and right vibration of the wheels, and
the torque Fxa is applied in the axial
direction. To correct the dynamic
unbalance, add the balance weight of a
same weight for two points of the
circumference of the rim, A and B, as
shown in the figure 2 (b), and apply the
torque in the opposite direction to the
torque Fxa to offset in order to ensure
smooth rotation of the wheel.
Center
a
a
Fxa
Fxa F
F
A
B
(a)(b)
[Figure 1]
[Figure 2]
3. WHEEL BALANCE
