Why are wheels balanced?

Most motorists, if not all of them, know the answer to this question: a wheel’s mass has to be evenly spread around its centre, and only then is vibration in the wheel kept to a minimum.

But why is that needed, and how can it affect durability, safety, comfort and other things that matter to us? Without going into detail, a simplified answer to this question might run something like this: if a wheel is not balanced across all its axes of symmetry, unbalanced centrifugal forces arise with different directions of action, which creates vibration in the wheel and loads on the hub pulling in different directions. This, in turn, leads to the following consequences:

1. Under loads the car maker never intended, the load-bearing parts of the suspension wear out much faster (it is usually the wheel bearings that suffer first), and if such loads increase significantly there can even be a risk of those parts suddenly failing. I do not think losing a wheel at high speed needs any further explanation.
2. A vibrating wheel has considerably worse grip on the road (an unstable contact patch), which leads to worse handling and a longer braking distance. All of this considerably lowers the level of driving safety.
3. Uneven loading of the tread caused by the wheel’s vibration considerably shortens the tyre’s service life: the tyre simply wears out faster.
4. And finally, strong vibration in the front wheel is passed to the steering wheel, creating discomfort for the driver.