I have heard that the back (side of the wheel) offset is stamped on the rims. I saw this on my Crossfire but have not seen it on the wheels on my Cobra. For the same purpose I called the maker of the wheels yesterday, ET (Team 3) to ask what the offset was and they told me you simply take off the the wheel lay it front side down on a protective surface. Lay a straight edge across the top most part of the wheel where it meets the tire then measure the distance from the back of the hub to the staright edge and that's your rear offset. Front offset is measured the same way, flip the wheel and tire over, lay your straight edge across the outermost part of the rim and measure from the back of the hub. Crossfire wheels are in metric. Hope this helps.