Proper frame alignment is critical in order to ensure normal life and functioning of many parts of the vehicle. Inspect the frame alignment if the vehicle has been involved in any of the following circumstances:

Inspect the frame alignment if you suspect misalignment for any other reason. Refer to Checking Frame Alignment .

The following terms are used throughout the frame and bumper section:

Section Modulus: Section Modulus is a measure of frame strength based on the height, the width, the thickness, and the shape of the side rails. Section Modulus does not account for the strength of the material used in the frame.

Yield strength: Yield strength is a measure of the strength of the material, of which the frame is made. Yield strength is the maximum load in kPa (psi) that may be placed on the material and still have the material return to the original shape.

Resistance to Bending Moment (RBM): Resistance to Bending Moment (RBM) is a single measure of frame strength that accounts for both the section modulus and the strength of the material used. RBM is the product of the section modulus and the yield strength.

Sag: Sag refers to a frame or a side rail that is bent down from where the frame or the side rail should be.

Buckle: Buckle refers to a frame or a side rail that is bent up from where the frame or the side rail should be.

Diamond: Diamond refers to the condition where one frame rail is moved forward from, or to the rear of, the frame or the side rail's correct alignment with the other rail.

Twist: Twist refers to the condition where the entire frame has been twisted. One rail will slope up, while the other rail will slope down.

Sidesway: Sidesway refers to a side rail that is bent to the side of where it should be.

Tracking: Tracking refers to the alignment of the vehicle axles with each other. A misaligned frame may cause improper tracking. If the vehicle is tracking correctly, all of the axles will be parallel to each other and perpendicular to the centerline of the frame.

Web: Web refers to the vertical part of a channel-type frame rail.