Wheel Unbalance

Off the top of my head....

1. The rim is bent

2. The rim is not assembled properly

3. The tire is worn oddly

4. Wheel & Tire are not balanced

5. Tire tread isn't designed for high speed

6. Wheel is not mounted to the truck correctly.

Again, not enough information. You are talking about two separate problems. Unbalance is where the tire bounces on the road as you drive, and wobbling caused by the tire not being concentric. Think about this. If the tire is not concentric to the center of rotation, it can still be balanced by adding enough weight opposite the out of round condition.

If you feel vibration in the truck as you drive it, the tire needs to be balanced, if you just see the wobble, then the tire is not concentric and needs to be replaced.