TB 9-2320-335-13&P
32-4. FRAME INSPECTION AND REPAIR (Cont'd)
(b) Horizontal (bowing) measurement.
(1) Select a smooth, level surface and drive vehicle into position from a 12 ft (3.7 m) straight line
of travel. Apply parking brake gently to bring vehicle to a stop. Chock wheels (TM 9-2320-
387-10) and release parking brake.
(2) Measure height of frame rails (3) and (6) at each end near center of crossmembers (2) and
(4). If heights vary by more than 1/8-5/16 in. (3-8 mm), raise and install jackstands to bring
frame to leveling tolerance (step 2a (1) and (2)).
(3) Hold a string with plumb bob (7), as shown, along frame rail (6) at intersection of
crossmember (2). Mark location (8) where plumb bob (7) stops moving. Repeat for other
three corners of frame.
NOTE
Strings used for horizontal bow measurement will remain in
place until procedure 2(c), frame skew, is completed.
To ensure measurements are precise, string must be pulled
tight and secured.
(4) Stretch string tightly on ground (5) between front and rear plumb bob (7) marks under each
frame rail (3) and (6).
(5) Measure front (2) and rearmost (4) crossmembers to determine center point. Drop a plumb
bob (7) from these points to the ground. Mark location where plumb bob (7) stops moving.
(6) Stretch string tightly on ground (5) between front and rear plumb bob (7) marks under
crossmembers (2) and (4) to determine centerline (1).
(7) Measure an equal distance (D) along right and left strings to select your measure points
and measure from these right and left points to center string. Mark these points on string.
The distance from right and left points to center string should be within 1/4 in. (6 mm) of
being equal. If not, one frame rail is bowed. Repeat this procedure for several other points
along frame. Record deviations.
32-6