wheel backspacing

[55 Tony]

I always seem to mix this up so I'll look dumb and ask.
My current 8" wide wheels have a 3.75" backspacing and could go out toward the fender 1/2" to be centered.
So I want to get 2 wheels for slicks, should I try to find 8" ones with 4.25" backspacing?

[chevynut]

To go further toward the fenderwell (quarter panel) you would want LESS backspacing, not more. Backspacing is measured from the backside of the wheel flange to the wheel mounting surface. So to move the wheel center outboard, you would want less backspacing.

Lots of guys get wheel backspacing and offset messed up. That's why I prefer to talk about offset, and not backspacing. Here's the catch....an 8" wheel's center is NOT at 4" from the wheel outside edges. An 8" wheel is actually about 9" wide outside the wheel flanges because the 8" is measured where the bead seats. So the center of an 8" wheel is at 4.5" backspacing, or ZERO offset. The center of any wheel is at zero offset. Your current wheels have 3.75" backspacing which is -3/4" offset. It's negative because the mounting surface is INBOARD of the center. A 4.25" backspace wheel would have -.25" offset. Positive offset is when the mounting surface is outboard of the wheel center. Some wheels are only sold with offset specified, and not backspacing, so it's important to understand this.

[BamaNomad]

Nice explanation CN...

[55 Tony]

Thanks, I got it. For now anyway.