There are a couple of reasons that balancing may not answer the problem. First, balaicning off the car with a computer balancer is, well, off the car. It does not adress how the wheels attach to the car. Computer balancing is the best though well over 99.99 percent of the time. The other is that it can be perfectly balanced and still be out of round. When that happens you will still get a hop no matter how well balanced it is. Picture a well balanced square wheel as it contacts the road.
