Bryon, Very easy to do. Take the wheel and lay it on a flat surface, outer side down. Then lay a straight edge(piece of wood will do) across the center of the wheel. Measure from the mounting surface(that contacts the drum or disc when the wheel is mounted) up to the straight edge. That is your backspacing. This is much easier to do without a tire mounted on the wheel. If a tire is mounted the straight edge has to be the same as the rim diameter so that it will lay flat. Most Buick factory rallye wheels have 4-4.5" backspacing. Hope that made sense.
