More than 14,000 little shakes an hour
be aware that what might  seem to be a very tiny, insignificant event, can easily become something of importance
This means that in just one hour driving, one wheel can deliver more than 14,000 of these little shakes.
Now start adding the other wheels on the car, multiply by hundreds of 
miles driven in a day and then start factoring-in the holes, bumps, 
rocks, debris, and other things a car may encounter on the road and you 
can see that the numbers start growing to incredible proportions.
It's not necessary to calculate all the thousands or even millions of 
vibrations which a vehicle could experience, because the exact number 
isn't important. What is important is simply to be aware that what might
 -at first glance- seem to be a very tiny, insignificant event, can 
easily become something of importance once you take into account the 
tremendous number of times this event is repeated in a vehicle which is 
being used under ordinary driving conditions.
When should balancing be performed?
People often notice unbalanced tires when they are on the front wheels 
because the vibrations are transferred through the steering wheel to the
 driver's hands. These same vibrations are not felt when they are on the
 rear wheels, but the fact that the driver isn't aware of them, doesn't 
mean they aren't affecting the mechanical wear-and-tear of thevehicle. 
This is why it has become a standard practice to balance every 
new tire at the moment it is installed, regardless of which position it 
will occupy on the vehicle.