Originally Posted by alistairolsen
Just to clear this up....
in-set, or backspace is the distance from the inner edge of the rim to the hub face and determines your inner arch clearance. This is a function of offset and width and is what youre concerned about benn to stop them hitting your tie bars.
Offset is the distance from the wheel centre to the hub mounting face and determines how the car handles with respect to scrub radius and various other geometric considerations.
When you widen a wheel on only one edge of the rim, the backspace doesnt change, so it will clear the inner arch, but the offset changes, so it will handle like a bag of ****e.
This is why most folk building 8" + wheels use them only up pod with slicks in a straight line, and most people on track stick to 7 inch wheels with an offset of more than 45mm as this is the max width that can be accommodated if you add the same to both edges before you run into issues with tiebars and the inner arch.