[Mike C]

Off set is a little different than backspace, but basically same thing. For example, I have 16x7 Centerlines on my Datsun. They are a zero offset wheel. with 4" backspacing. While that seems an anomaly, the thickness of the seating bead part of the rim adds about 1/2" to the wheel on each side. So the overall width of the wheel is 8" even though between the beads is 7" where the wheel is measured. Thus the mounting flange of the wheel is exactly in the center, or zero offset, whild backspacing is 4". Backspacing is measured from the outside of the wheel not the mounting bead and offset is distance from centerline that the mounting flange is moved. Positive offset moves the wheel out while negative offset moves the wheel in relative to the center.