In every tyre, old or new, there are small irregularities that throw the tyre out of balance. These differences are generally very small, but when driving, the radial force creates an imbalance. This then becomes noticeable in the driving comfort. The steering wheel or even the whole vehicle vibrates. There are two different types of unbalance: static and dynamic.
Static unbalance
Static unbalance means that the tyre moves up and down because there is a difference in weight on the bottom of the tyre compared to the top. When the tyre rolls, the forces are not distributed properly and the tyre swings up and down vertically. If the tyre rotates faster, this effect is amplified. This usually manifests itself in a vibration of the entire vehicle.
Dynamic imbalance
Dynamic imbalance occurs when there are irregularities of the tyre in the horizontal plane. For example, when the left side of the tyre is heavier than the right side. Again, the effect increases at higher speeds. This then becomes noticeable mainly through vibrations in the steering wheel.