How to measure backspacing on your custom forged aluminum billet wheel:
When you're shopping for your new custom forged aluminum billet wheels, you'll see a range of backspacing, offset and width measurements available for your vehicle. When looking at billet wheels, sometimes the measurements from your stock wheels are listed, but sometimes they are not. This may lead you to wonder, "How are these measurements going to change the stance of my car?" Without knowing what you currently have, it's tough to know how far in or out your new custom wheels will sit. If the backspace is not stamped on the back side of your wheel and your research has you still feeling empty, you can measure the backspacing of your current wheels at home.
1. Place the wheel, face down, on the ground (preferably on a towel or blanket so you don't scratch the aluminum face)
2. Get a straight edge that will span from lip to lip Measure from the bottom of the straight edge straight down to the mounting face of the wheel.
3. The distance from the mounting pad to the straight edge is the backspacing of your wheel. The picture below shows an example of a 4.5" back space.