Offset math

I have read and read post from years and years ago trying to determine what I want in a wheel and tire. One thing I keep seeing is people are saying get an 8inch wheel with 0 Offset and 4.5 backspacing. That math doesn't add up. 0 Offset would be 4 inch backspacing. It is all over this forum and I can't seem to figure that out. I have a 2015 with 2.5 inch lift and want 285/75/16 KO2's. Looking at a 16x8 with 1 mm offset.

 

Welcome to TW. Sub'd.

 

welcome to tacomaworld. Hopefully somebody with some good solid info will drop by shortly.
from what i understand, a wheel with a -12 offset gives you 4.5" of backspacing.

 

Welcome aboard. I didn't see a question in your first post but I am assuming you want clarification of backspacing. You are correct that an 8" wheel with 0 offset will have 4" of back spacing. Offset and back spacing measure the same thing (the location of the wheel to hub mounting surface in relation to the wheel itself) but from two different reference points. Offset is measured in mm from the centerline of the wheel (looking at it from the front or rear of the vehicle). A wheel with negative offset will have the mounting surface closer to the inside edge of the wheel, thus pushing the wheel further out of the wheel well. A wheel with positive offset will have the mounting surface closer to the outside edge of the wheel this moves the wheel closer to the vehicle and deeper in the wheel well. Backspacing is measured in inches and if you imagine laying a wheel flat on the ground on it's face and you lay a straight edge straight across the lip of the wheel. The measurement from that straight edge to the mounting surface is the backspacing. The less backspacing, the more the wheel will stick out from underneath the vehicle. More backspacing tucks the wheel deeper in the wheel well.