ok, i need someone to clarify something for me....
if offset is the distance from hub mounting flange to the centerline of the wheel, and.....
if backspacing is the distance from hub mounting surface to the inside lip of the wheel,.....

then how is it possible for a 9" wide wheel with 5" backspacing to have a 0 offset?

if the offset is 0 in this case, then wouldnt the backspacing have to be 4.5", and then the other 4.5 inches be on the outside of the wheel, since both measurements are being taken from the same point (hub mounting surface=centerline of wheel).

im a little confused on this issue i think.


thanks !!!

 

They are two differnt things. (Some rims manufactures post the offset variance from factory desigend rims as well)

Offset. The distance from the centerline of the wheel to the face of the mounting surface of the wheel that contacts the hub.

4.1 Zero Offset. Indicates the mounting surface is at the wheel center.

4.2. Negative Offset. Indicates the mounting surface is behind (or inboard) the centerline of the rim. This is often found on standard rear-wheel-drive vehicles and on so-called reversed rims. (Diagram below shows negative offset)

4.3 Positive Offset. Indicates the mounting surface is in front of (or outboard) the centerline of the rim. This is often found on front-wheel-drive vehicles. Stock Tacoma wheels have Positive offset.

5. Backspacing. The distance from the mounting surface to the inside lip of the wheel. This measurement is closely related to offset (without actually measuring, backspacing is about equal to [Wheel Width / 2] + [Offset] + [about 1/4] ).

From this site: http://www.customtacos.com/tech/index.php?article=40