OOSC, Part II, Item 11. Suspensions - Axle Positioning Parts

On many common log truck frame trailers, which we refer to as bunk trailers, there is a single point suspension system in use that involves a heavy-duty leaf spring assembly attached to each tandem axle at the ends, and a single securement point (dead axle), secures this assembly to the frame of the trailer. There are two clamps that secure the tandem axles to the frame of the trailer. Each of these clamps have 8 bolts that secure this dead axle to the frame. On each side there are 6 bolts on the dead axle clamp itself, and two bolts that secure the top of this clamp to the frame. This dead axle is attached to each side of the tandem axle in the middle of the heavy-duty leaf spring assembly and is how the tandem axles attach to the frame. Without these clamps and bolts effectively secured, a catastrophic failure of the suspension can take place where frames have been known to unexpectedly roll off the axles in turns. This results in an accident that likely rolls the truck and trailer over unexpectedly at highway speed when it is in a loaded state.

Current out of service criteria does not specifically address this dangerous condition for this type of suspension system unless the axle member is "any U-bolt(s) or other spring to axle clamp bolt(s) cracked, broken, loose, or missing" OR “other axle positioning part cracked, broken, loose, or missing resulting in an axle shifting from its normal position." The latter part of this is what is shown typically, but after an accident has already occurred. Other items listed within the suspensions area of the out of service criteria do not appear to be applicable. Having loose or missing bolts on the frame to axle brackets are many times a violation that inspectors cannot place out of service unless it meets the narrow description provided in criteria. With an update to out of service wording, inspectors will be better equipped to place these trailers out of service before an accident occurs due to this condition. This is an easy maintenance fix with the proper parts and equipment.

Update out of service criteria to include " when any frame to axle positioning part is broken, loose or missing" or add a section that is applicable to single point suspension systems