Measuring your car for wheels and tires can be a real pain. Nobody likes ordering wheels and tires only to find that they don't actually fit when you get them in. It happened to me a few years ago, so I built this tool so that it would never happen again. It is as simple as it gets, but it works really well. You still have to do some math, but this tool allows you to check clearances to the frame, suspension, fenders, etc without having to buy test wheels.
To make the tool, you just need a couple of pieces of extruded aluminum angle, some 1/4-20 all-thread, and a couple of 1/4-20 nuts and bolts.
This tool works really well for wheel and tire fitment measurement, and will save you a lot of headaches when it comes time to order wheels and tires for your ride.