Measuring Wheel Backspacing
We get all sorts of questions here at the Speed Shop, and one of our most common questions involves fitting custom wheels and tires. To get the right look, you really need to study your car, and make some important measurements. It’s also important to know the particular measurements if you’re planning to do your wheel and tire shopping at a swap meet. Always carry a measuring tape with you, so you can get a quick measurement.
A straight edge and measuring tape (or two measuring tapes) can give you an idea of your fitment. Place one tape on the plane of the wheel mounting surface, and then measure to the inner fender. You always want to give yourself a couple of inches to compensate for the “bulge” of the tire sidewall. If you’re running a narrow wheel and a wide tire, the bulge will be more significant. For this application, it looks like we can run about 5 inches of backspacing on our wheel.
To measure for the front spacing of the wheel, just reverse the process. Drop the tape or straight edge from the outer most point of the wheel opening and then measure from there to the mounting surface. Looks like we can get away with about 2.5 to 3 inches of front spacing on this application. That means we could easily fit an 8-inch wide wheel under the rear of this car, and then match it with a 235/75R15 tire or something similar.
When it comes time to do some swap meet scrounging, keep your measuring tape handy. You can usually eye ball it, but it helps to have two tapes or a straight edge. Lay the straight edge across the wheel, and then measure from the mounting surface to the straight edge. This one is showing 4.25 inches of backspacing, which will be perfect for our application.