I have done countless hours of research in preparation for buying my new wheels, and I thought I understood the relationship between offset and backspacing. I recently found this chart that converts offset into backspacing using wheel width, but it doesn't quite make sense.

The way I understand it, offset is the distance between the center of the wheel and the mounting surface of the wheel. Backspacing is the distance from the back lip of the wheel to the mounting surface.

If this is correct, then a 10" wide wheel with 5" backspacing would have 0 offset because the mounting surface would be right at the center of the wheel, right? The same theory says that a 9" wide wheel with 4.5" backspacing would have 0 offset, and an 8" wide wheel with 4" backspacing would have 0 offset. Basically, divide the wheel width in half to find backspacing if the offset is 0.


This chart tells another story. According to it, a 10" wide wheel with 0 offset has 5.5" backspacing. How is that so? It says a 9" wheel with 0 offset has 5" BS, and an 8" wide wheel with 0 offset has 4.5" BS.

Here is a link to the chart I mentioned. When the page pops up, scroll down to see it. http://www.thewheelconnection.com/cu.../tech-help.php

What gives? Can someone help clear this up for me?
Thanks
Brian

 

The link isn't working. Maybe the chart is just wrong because you are correct.

 

My understanding of backspacing is the same as yours,The outside of rear lip to the mounting surface,However offset is from center of wheel to mounting surface(also what you said)The key difference is wheel width is measured from between the beads(not to the ouside of the edges of the wheel),so the half inch difference is the distance from outside edge of the wheel to the inside of the bead.I am not an expert,and I could be mistaken but that is how I understood it. Here is a link to a chart that shows this

http://www.wheelsforless.com/offset_diagram.asp

 

Ahhh. That explains it.