TM 9-2320-361-34 13-3. FRAME ALINEMENT INSPECTION (Contd) e. Vertical Bow Inspection, Frmnes20 Ft (6 M) or Less 1. Stretch string on floor and position weight under bottom and at front of frame rail (1) or tie ends of string to jack stands. Pull string tight. Position weights or jack stands at 20 ft (6 m) measurement. 2. Measure distance between string and bottom of frame rail (1) at closest point to each weight or jack stand. Adjust string height until each measurement is the same and the entire length of string is unobstructed. 3. Measure distance between string and bottom of frame rail (1) near crossmembers (2) and as close to the midway point as possible. If frame rail (1) bows more than 1/8-5/16 in. (3-8 mm) up or down, the frame rail (1) is out of tolerance. NOTE If measured frame rails are out of tolerance, notify supervisor. If frame rails are verified to be out of tolerance, truck will be classified as unserviceable. f. Vertical Bow Inspection, Frames 20 Ft (6 M) or More NOTE On trucks with a frame longer than 20 ft (6 m), the front 20 ft (6 m) of frame rail (measured from front to rear) and the rear 20 ft (6 m) of frame rail (measured from rear to front) are measured separately. This will cause an overlap in measurement. Perform subtask e for each 20 ft (6 m) section of left and right frame rails (1). 13-10