Why does my trailer suspension keep breaking?

[Cord]

Several years ago I rebuilt my 10,000lb flat be trailer. New tires, fenders, springs, lights, ect. To do this work I flipped the trailer over. At that time I noticed that some of the spring mounts were rough so I replaced them. Fast forward a few years later... I had loaded my skid steer (7,000lb machine) and made a u-turn when I heard a "bang!". Stopped to check the trailer and found the left rear spring shackle had broken off. The weld did not fail, instead the the two tabs ripped right off the U. Attributed that to a freak occurrence until last night. I had just transported the same skid steer 2.5 hours at 75mph without an incident. Unloaded the machine and transported the trailer 15 miles, some of which was over a very rough road. When I got to my destination I could smell something hot. Check the brakes and they were cool. Noticed the tires were shifted together and had burned each other down significantly. Sure enough the right rear spring shackle broke off. Same shackle and before, but now the opposite side. It was dark or I would have taken a picture. Just like the last time, the tabs broke off the U, but the welds held. The break is very jagged, like the metal ripped. The break is bright and not rusted. Definitely not the result of a brittle weld. WFT is going on here?

 

[CJONE]

I would say without looking at the whole trailer is a misalignment under load. CJ

 

[Billrog]

The tires are dragging on very sharp turns cause to much side tension. I've often wondered why more haven't broke when I see travel trailers in parking lots doing sharp turns and the wheels torching out of alignment. This would be most detrimental when loaded.

 

[Ed of all trades]

It sounds like either the shackle was to light or the weld was wrong in some way you don't see or both. Did it break at the weld? how big was the grain in the metal at the break? Ed

 

[GPintheMitten]

Just a guess but I agree that sharp turns but a heavy load sideways.

 

[Redneck in training]

Possibly wrong material the part is made from.

 

[Diamondpilot]

Never seen that one. Perhaps you bought replacement ones that were "cheap"

Chris

 

[zzvyb6]

What are you running for air pressure in the tires ? Increasing the pressure will lessen the tire scrub. How close are the axles ? Decreasing the distance will lessen the tire scrub.

Rough road damage is fatigue (coat hanger).

 

[Raspy]

It seems pretty clear that your replacement spring mounts are not strong enough. A 10,000 lb gross trailer with a 7,000 lb load is probably at the max GVW.

Is it really a good idea to tow a fully loaded trailer at 75 MPH? I think that endangers everyone else on the road.

 

[Tractor Seabee]

Obviously too much load for the load bearing parts. Could be as simple as the U bolts not being torqued; right allowing them to work harden combined with unrealistic speed (stress) and rough roads (again adding stress). My trailers never go over 60 and that is only on the freeway. Yeah, people honk and give the one fingered salute, but I may be saving their life.

Ron

 

[farmer2009]

I did the same thing a couple of years ago. I think I did mine hauling hay with the tractor. It was on a 7k axle. When I welded the new one back on I added a piece of angle iron on one side of each hanger. Welded it to the hanger and frame. Kind of as a support. I seen the angle iron idea on a different brand trailer of the same weight.

 

[bcp]

Standard trailer spring hangers have always underwhelmed me. They seem like the weak point in the suspension system. Most are much weaker looking than 1/2 ton pickup hangers.

Spring Mount | etrailer.com

Bruce

 

[Cord]

I agree I think these are breaking because of the axles scrubbing when I turn. The break looks like a piece of thick paper that was torn lengthwise. Very jagged and uneven. If it was a bad weld, I'd expect the break to follow the heat line and have a crystaline appearance. The axles are pretty standard spacing using a idler link in the center. The tires are at 80psi and the 12k springs causes the trailer to ride rough when empty. I was thinking of a way to try and reinforce the brackets, but the frame is a channel which is open to the inside and the fender braces are on the outside. I also thought about having the fabricator make the bracket in a thicker material, but I didn't want to remake the other bracket that he repaired previously. I sourced the brackets from etrailer and havn't had any problems with quality in the past.

 

[GLyford]

I was thinking of a way to try and reinforce the brackets, but the frame is a channel which is open to the inside and the fender braces are on the outside.

One option would be to add a web stiffener between the top and bottom of the channel to bring it out flush. Could be just a section of strap or plate the same thickness as the channel flanges, or could be a length of angle or tube. That will at least keep the channel from flexing as much where the bracket attaches.

I am not sure how the angle farmer2009 describes is running, whether it is vertical from the bottom of the bracket to the top of the frame, or horizontal behind the bracket tying the two sides together and also up the frame. I want to say I have seen someone's trailer done that way where the angle goes clear across the frame, tying all 4 bracket sides together and also keeping the channel sides from flexing. Don't know how in-the-way that would be for you.

On the outside, maybe a gusset to your fender brace: if it's solid and in the way, make use of it?

 

[farmer2009]

Sorry if I wasn't clear on my description. The angle runs under the frame across the trailer. Here's some pictures. I did this for both axles.

 

[farmer2009]

Only one picture per post.

 

[GLyford]

Yep, I like that.

 

[triptester]

The shackle may be breaking due to improper welding. When welding on the side of the brackets with the radius under cutting of the hanger material may occur weakening the hanger material.

 

[JJZ 109]

Never seen that one. Perhaps you bought replacement ones that were "cheap"

Chris

Kind of what I was thinking. Metal fatigue?

 

[ch1ch2]

You said you bought new tires.
Could they be a bigger size?
The problem started after you made improvements.