quote:One tiny note on David Nunn's excellent drawing: not all wheels have the outboard 'bump' for wheel weights or whatever on the extreme edge of the rim, so technically, the backspace should go from the flat part of the wheel to axle flange rather than including the bumps. Sure, all Campys have them, but aftermarkets, steel etc vary all over the map as to the heights of bumps or whether they're there at all. Thats also why some people get 4-3/16" for 8" Campy backspace while others get 4". Just a thought for consistency.
Excellent point. My aftermarket rims don't have that extra lip. So instead of an extra 1/2 on each side like the drawing, mine have approximately 1/4 extra on each side. So my 9 inch rims measure 9.5 inches from the outside to the outside portion of the rim. They measure 9 inches where the tire seats.
My rear 12 inch rims measure 12.5 from the outside lip to the outside lip.