Checking Frame Alignment

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The main components of the frame are the side rails and the crossmembers. The rails carry the load. The crossmembers stabilize the rails.

The 5 types of frame misalignment are the following:

Sag
Buckle
Diamond
Sidesway
Twist

A misaligned frame rail may move in the following directions from where the frame rail should be:

Forward
Up
Down
To the side

The easiest way to inspect the frame alignment is with gauges that are made for this purpose. Detailed instructions are normally supplied with the gauges at the time of purchase. There are no instructions for gauge use in the manual.

Whether you inspect the alignment with or without gauges, park the vehicle on a level section of floor.

Certain conditions call for preliminary inspections before inspecting the frame. Suspension or axle problems may make it appear that the vehicle frame is out of alignment. If an axle has shifted, diamond or sidesway may appear to exist when neither do exist. A weak spring may make the vehicle appear to have a twisted frame.

A visual inspection of the top and the bottom flanges of each rail may reveal the specific area where the sag or the buckle exist. In the case of a sag, wrinkles may appear on the top of the upper flange. The wrinkles are definite evidence of sag. Wrinkles on the bottom of the lower flange are definite evidence of buckle.