# Wheel Balance Vibration and Sounds

Due to the weight unbalance of the rotating object, a centrifugal force is generated during rotation, which results in a vibrating force.
This vibrating force increases in proportion to the square of the rotation speed increase. If the tire is not well-balanced, vibration such as shake or flutter may occur.
This is caused by the weight imbalance in the tire or the wheel.
It is also affected by the assembly condition for the tire and the wheel.
Wheel balance is divided into static balance and dynamic balance. When either of these balances are insufficient, the tire vibrates and causes shake or flutter.

Wheel Balance
1.Static balance
Static balance is the weight balance from the wheel center in the direction of the radius.
When attaching the weight W1 to the disk installed in the rotating shaft, this disk rotates until the W1 stops at right in the center of the bottom. In other words, it is not balanced statically. This condition is referred to as “the static balance is lost”. In order to keep this balance, attach the same weight as the weight W2 at the same distance of the opposite side at 180 degrees. So this disk remains static in any position. This condition is referred to as ” the static balance is kept”. Static balance results in the radius vibration.
2.Dynamic balance
While the static balance is the balance when the tires are not rotating, the balance during rotation is referred to as the dynamic balance.
The disk is not statically balanced. However, considering that these two disks as one unit, static balance remains as long as the W1 and W2 are positioned 180 degrees apart, at the same distance from the center, and with the same amount of weight.
When rotating these disks, the direction of the centrifugal force applied to the W1 and W2 are different by 180 degrees. Therefore, the rotating shaft generates power to vibrate the shaft around the line connecting each disk’s center of gravity G1 and G2, which results in vibrating the disk right and left.
One way to balance these disks is to balance the W1 and W2 static balance independently.
Dynamic balance results in lateral vibration.