Hi Jason94sport:
From your post, it appears that a few definitions are in order.
Offset is the distance between the wheel centerline and the mounting surface of the wheel. Increasing positive offset moves the centerline of the wheel out from the center of the vehicle. Said another way, positive offset puts the wheel mounting surface inboard of the wheel centerline. Many fwd vehicles use wheels with negative offset, which puts the wheel mounting surface outboard of the wheel centerline.
Backspacing is the distance between the wheel mounting surface and the inner wheel lip. Backspacing is always positive unless you are using wheels from a dually.
To make use of these terms, you have to also know the width of the wheel.
If you know any two, you can figure the other with the following:
offset = (width / 2) - backspacing
backspacing = (width / 2) - offset
width = 2 * (backspacing + offset)
Note that width and backspace are usually given in inches, and offset in millimeters, so you also need:
1 inch - 25.4 millimeters
When comparing wheels, two wheels with the same backspacing will have the same clearance to suspension components (assuming the same wheel diameter), regardless of width or offset. Two wheels with the same offset will load the wheel bearings similarly and not change the suspension geometry (assuming the same tire diameter), regardless of width or backspacing. Two wheels with the same width can run the same width tire (assuming the same wheel diameter), regardless of backspacing or offset.
I hope this helps.
Regards,
John.
