I spent a lot of years teaching wheel alignment and balancing, and rotating the tire to different locations on the rim is a good way to minimize the weight necessary to bring a wheel/tire assembly into balance. Due to manufacturing tolerances, some tires can be very difficult to get into acceptable balance. Another sneaky trick is to static balance the wheels separate from the tires, using stick-on weights inside the barrel area of the wheel. Then all the spin balance does is correct the dynamic imbalance of the tire. I have a very sensitive set of ball bearings on a support shaft to static balance wire motorcycle wheels, using solder or lead wire wrapped around some of the spokes.
Jerry
