David,

I too have seen that number but somehow backspace and offset are not the same number.

offset is the difference, positive or negative of the mounting face from the midpoint of the rim width: hence 7.5 inches div by two plus (or minus) 55mm...

I am trying to get the actual number on an actual wheel representing the bolt mounting face of the wheel and its distance from the inner edge of the wheel. Pretty sure that it ISN'T 55mm

Thanks for the help tho'

Hotshoe