Backspacing on wheels - how to measure

[70455ht]

I am a little comfused on how to measure the back spacing on a wheel. Is it the measurement from where the wheel mounts against the brake drum to where the tire mounts against the mounting flange of the wheel? Or is it the measurement from the where the wheel mounts to the brake drum to the very outside lip of the wheel? Any diagrams available that would show this?

[70 gsconvt]

Here's is the page with pictures from Wheel Vintiques. The bottom of the page has the pic about checking the backspacing on a rim as well as it's true size.

http://www.wheelvintiques.com/measure.html

Good luck.

Phil