Measuring for the correct wheel size/backspacing/offset?

[HotRodKush]

In my quest for new wheels for my Corvair, I quickly realized that nobody makes a bolt-in part for that car. That means that I need to check fitment, backspacing, etc. on my own BEFORE purchasing a set of wheels to make sure they'll fit. Is there a good guide out there somewhere that outlines the process for calculating the proper wheel fitment? I'd love to pick up a set of black steely Cragars, I just need to make sure I get the right measurements before buying them.

[Apogee]

There are various fitment tools that you can buy or make that can make the job easier, but nothing beats using real parts IMHO. The Percy Wheelrite (http://www.percyshp.com/WheelRite.html) does an okay job for personal use, however isn't quite as industrial as I like my tools to be.

Tobin
KORE3

[JRouche]

I made up a tire and wheel simulator. Its made from 3/16" plate and is pretty stout and easy to make. I can simulate a tire and wheel from 14"x7" up to 20"x 13" and everything in between. And some crazy offsets also. JR

[BlackenedRR]

Here's another product to think about, albeit a pricey one...

http://autowaretech.com/mountmate/