Shackle Straps Break on a 20ft Tandem Axle Trailer and the Rear Axle Slides the Tires

Question:

I have a lawn service trailer. It is approxmently 20 ft. with two 6500 lb. axles. My problem is the rear shackles keep breaking. Ive noticed in tight cornering the rear axle is sliding the tires. What is the proper repair for this situation?

asked by: Ace

Expert Reply:

One of the most common causes for shackle straps to break is over-tightening of the shackle bolts. If the shackle bolts are too tight, the shackle straps are not able to move with the suspension. This causes binding and it can bend or even brake the shackle straps, bolts and hangers.

The sliding that you are experiencing on the rear axle is common for tandem and triple axle trailers and it is usually called scrubbing. The rear axle scrubs because trailer axles are not steering axles, so the rear axle just drags behind the front axle when turning. Again, this is common and it should not be the sole cause of broken shackle straps.

The first step I would take is to ensure that all of the suspension components, leaf springs, equalizer, shackle straps and shackle bolts are an appropriate size for your trailer. If your leaf springs and/or equalizer are too long or short for your trailer, that could put additional stress on the suspension components. It may be best to take your trailer to a trailer repair shop and have them inspect the suspension and axles if you are not familiar with trailer parts.

If all of the parts seem to be in order, I would make sure the shackle bolts are not tightened too much. When tightening shackle bolts, they should be ran tight, then backed off enough to allow the leaf springs and equalizer to move between the shackle straps.

expert reply by: John H