For something so simple, determining the dimensions of a car’s wheel can be confusing, though it’s not difficult with the right approach. If the tires are still mounted on the wheel, and the wheel does not have its measurements imprinted on it, it may be difficult or impossible to determine its exact width. To determine wheel width, you need to remove the tire.
Loosen the lug nuts on a wheel. Lift the vehicle with a jack. Finish removing the wheel. If you think you have different-sized wheels on the front and back, then remove one front wheel and, after replacing it, repeat the process with a rear wheel.
Inspect the face of the wheel to see if there are size markings cast into the area between the spokes or near the holes for the lug nuts. If the size is there, it will be in two numbers, one for the width of the wheel one for the diameter. If it says “15 x 7,” then the wheel's diameter (the distance across the face) is 15 inches and the width of the wheel (the distance from the outer edge of the wheel to the inner edge of the wheel) is 7 inches.
Turn the wheel over if there are no markings on the front of the wheel for the size. Often, wheel manufacturers place the size and dimensions on the back.
Measure the wheel with a tape measure if there are no markings anywhere. Measure the distance across the face of the wheel from one edge of the wheel to the opposite edge. This will give you the diameter of the wheel in inches. It can be from 13 inches to 20 inches or more. Next, determine the width of the wheel from the inside edge of the outer lip to the inside edge of the inner lip. This can be from 4 inches to 10 inches or more.
