A man named Dennis Custer tells the following story about getting some new tires for his car.
“The man mounting new tires for me,” he says, “had no way of knowing that I am a mechanical engineer. As he worked, he asked, `Do you know why I put half of the weights on the inside rim and half on the outside?’ `As a matter of fact, I do,’ I replied. `The imbalance can be resolved to a point mass located in the plane of imbalance. If an equal mass is placed at 180 degrees opposite and at an equivalent radius, then perfect balance will result. However,’ I continued, `the plane of imbalance is located somewhere between the planes of the rims. By dividing the weights between the rims, you can approximate the ideal balance.’ The fellow stared at me for a moment and then said, `Yeah, ‘cause if you don’t, it’ll wobble.’”