Checking Frame Alignment

Checking Frame Alignment

The frame consists of the following components:

* The side rails carry the load.
* The crossmembers stabilize the rails.

Body misalignment is divided into the following types:




* Sag - A vertical misalignment that results in an incorrect datum line. Kick-up occurs when both sides of the frame are equally misaligned.




* Collapse - The condition that occurs when buckles appear on more than one surface of the box section of the side rail. Collapse is the condition that occurs when a section of the underbody or the frame structure has been shortened in length.




* Diamond - The condition where 1 side of the frame moves forward or rearward. The diamond then causes the frame structure to be out of square.




* Sidesway - A section of the frame positioned to the left or right of the centerline when compared to the rest of the vehicle.




* Twist - The condition where the sides of the underbody plane, datum, are not parallel. One rail slopes up while the other rail slopes down.

A misaligned frame may move from its proper position in the following ways:

* Forward
* Up or down
* To the side

Check all possibilities. The easiest way to check body alignment is with tramming gauges and universal measuring systems made for this purpose. Detailed instructions normally come with the equipment at the time of purchase. Refer to those instructions.

Always park the vehicle on a level surface. Certain conditions call for preliminary checks before you actually check the frame. The vehicle may mistakenly appear misaligned under the following conditions:

* When suspension or axle problems are present.
* When an axle shifts, causing a diamond or sidesway incorrectly to appear.
* When the springs are weak.

Visually inspect the top and bottom flanges of each rail. This step may reveal the specific area where sag or a buckle exists. In case of a sag, wrinkles may appear on the top of the upper flange. Wrinkles on the bottom flange indicate a buckle.