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9 Measuring wheelbase with the string method is also simple. Use a framing square as you see here. The angle this photo was taken makes it look misleading, but here Wallace has one end of the square aligned with the string and the outside edge of the other pointing to the center of the hub. Now using a magic marker he marks the string and repeats the process at the back of the car. Once those two marks are made, he can measure the distance between the two to determine his wheelbase. Alternatively, you can hang a plumb bob from the center of the hub and mark the spot it points to on the floor. Determining the wheelbase can help you achieve proper rear alignment which is critical to a good setup. Proper alignment is a squared rear end to the center of the chassis. Of course, we’re only talking about small movements here—usually in the range of 1/8- to 1/4- inch at most.