bottom, but from side to side. You can not move a weight from the outside to the inside (or inside to outside) without causing balance problems. This is even more pronounced on extra wide tires. When looking at a tire mounted on a car, the tire can be heavy at the top. The extra weight can also be on the outside edge and not evenly distributed across the tread. By moving the weight from the outside to the inside (or vice versa), you can make the out of balance even worse.