What is balancing tires?
Balancing tires is done with whatever method the shop has available which for some is on the car and some shops off the car. Both simply find heavy sides to a tire and wheel combination and they add weight to the other side. If you look into it you will find there are many ways a tire can be out of balance which each of them will cause a vibration or even hard shake at certain speeds. The best balance involves inboard and outboard weights but this is beyond the needs of most driving so most shops simply add weights to the back side so as not to show.
