John, that picture is how I tried to describe measuring backspacing. Maybe you did not undertand me or I did not explain the directions properly in my original response. I guess that the top of the bead area would be flush with the back of the wheel. We would both use two different techniques to...
Backspacing is not measured using the back edge of the wheel to the mounting flange. You lay something inside the bead and measure from the mounting flange to that.