What causes this? Tandem trailer shackles flipping

[FTG-05]

Ok some actual data from my trailer axles:

Axle tube diameter = 3" (5200-6000 lb axles per etrailer) https://www.etrailer.com/question-137312.html
Hanger to hanger length = 30.25" front and 30" rear
Spring length eye to eye = 26"
Hub to hub = 34.25"

Per Dexter's Leaf Spring Application page #64 of their 6000-8k Complete Catalog for 26" springs in a tandem configuration Home | Dexter Axle Co:

Hanger to hanger should be: 30.50"
Hub to hub should be: 35"

So what this tells me is: Hangers are a little too close by 1/4"-1/2", hence hub to hub is a little short by 3/4".

Bottom line: Springs are not too short for this configuration.

One measurement I do not have right now is the equalizer spacing measurement. However, the catalog does not show what that measurement should be either.


BTW: by looking at a few YT videos, it's rather easy to return the spring shackles to their proper configuration. With the trailer flat on the ground, lift the axle with the correct shackle orientation. The incorrect shackle will snap back.

 

[Xfaxman]

I had a trailer with that problem.

I added bump stops above the shackles to stop the equalizer's upward travel so the shackle couldn't flip.

 

[FTG-05]

I had a trailer with that problem.

I added bump stops above the shackles to stop the equalizer's upward travel so the shackle couldn't flip.

Funny you should mention that:

I ordered them a week or so ago. Got them installed (mostly), haven't driven it yet to see how they do.

Since you added the bump stops, has the shackles flipped at all?

Thanks,

 

[Xfaxman]

-----------------------------------------
Since you added the bump stops, has the shackles flipped at all?

Thanks,

No they can't flip. I made the bump stops about 36 years ago to stop the equalizer from going high enough to let the shackle flip.
They are mounted to the frame above the spring eye, like the red blocks that I drew:

I don't own the trailer now, so found this picture on the www.

 

[FTG-05]

Cool beans! I bet I have some poly bumpstops I could use. Thanks!

 

[gsawtell58]

Trying to add the Moryde Wet Bolt kit to my 12k tandem axle trailer. I get under there to work and I discover this:

When I got done with the other side, it immediately swapped sides and did the same thing. I flipped it around twice, but it flopped over opposite each other every time.

Reviewing pics on the 'net shows that it's supposed to look like this:

Trying to add the Moryde Wet Bolt kit to my 12k tandem axle trailer. I get under there to work and I discover this:

When I got done with the other side, it immediately swapped sides and did the same thing. I flipped it around twice, but it flopped over opposite each other every time.

Reviewing pics on the 'net shows that it's supposed to look like this:

What is causing this and what do I need to do to fix it. This probably accounts for why my trailer rides so crappy.

What is causing this and what do I need to do to fix it. This probably accounts for why my trailer rides so crappy.

In the picture it appears that the mounting angle of the righthand axle is rotated counterclockwise leaving the spring eyes at an uneven level.

 

[quarencia]

Bottom line: Springs are not too short for this configuration.

One measurement I do not have right now is the equalizer spacing measurement. However, the catalog does not show what that measurement should be either.

Without knowing length of the equalizer bar, the length of the shackles, or the height of the equalizer (vertical from center bolt down to the two outer holes when it‘s level) you can’t say with 100% certainty that the spacing is correct. Also need to know if the relative height of the frame mounts for the springs and equalizer are correct. All of the geometry matters. I bet if you took some pics and called eTrailer, they’d take the measurements and let you know if they think it’s ok. Especially if you bought wet bolts from them. It should work correctly without bump stops 99.9% of the time. For what it’s worth, I’ve never seen it happen on my or my fathers trailers. Nor any others we’ve ever used.

I have heard some “experts“ claim that slightly different spacing of the front and rear hangers can improve ride quality. I can’t remember which way they said it should be. IMO they were more experienced at emptying beer cans than building trailers so I wasn’t listening too closely.

 

[FTG-05]

Without knowing length of the equalizer bar, the length of the shackles, or the height of the equalizer (vertical from center bolt down to the two outer holes when it‘s level) you can’t say with 100% certainty that the spacing is correct. Also need to know if the relative height of the frame mounts for the springs and equalizer are correct. All of the geometry matters. I bet if you took some pics and called eTrailer, they’d take the measurements and let you know if they think it’s ok. Especially if you bought wet bolts from them. It should work correctly without bump stops 99.9% of the time. For what it’s worth, I’ve never seen it happen on my or my fathers trailers. Nor any others we’ve ever used.

I have heard some “experts“ claim that slightly different spacing of the front and rear hangers can improve ride quality. I can’t remember which way they said it should be. IMO they were more experienced at emptying beer cans than building trailers so I wasn’t listening too closely.

I never said the spacing was correct: I said the springs are not too short for this configuration. And I specifically mentioned I did not know the correct equalizer length nor does it show on the Dexter catalog diagram for either a 33" spacing or 35" axle spacing. The frame mount heights for the springs and equalizer are correct per the Dexter diagram. The distance between them is noted above.

 

[RandyT]

If you lift the entire trailer off the ground and put it on blocks you can flip those shackles any time your want. It allows the one axle to drop all the way down while the other axle pivots all the way up and they will flip every time. Most of the time unless you go through a really unlevel area you will never flip them in normal use. I flipped mine once while jacking the hitch up but flipped back over when the hitch was lowers. And that was with all factory parts.

 

[FTG-05]

If you lift the entire trailer off the ground and put it on blocks you can flip those shackles any time your want. It allows the one axle to drop all the way down while the other axle pivots all the way up and they will flip every time. Most of the time unless you go through a really unlevel area you will never flip them in normal use. I flipped mine once while jacking the hitch up but flipped back over when the hitch was lowers. And that was with all factory parts.

It's a lot easier to just lift the axle that is in the correct configuration; don't even have to take the tire off or anything.

From reading on the internet, plus various trailer sites, this is a very common occurance apparently; no forked up trailer construction or design needed. It almost always happens when unloaded and going over a fairly big bump - like a curb. Some people even report fixing it by going over another bump or curb to return it to it's correct configuration.

BTW, I towed my trailer a couple days ago to go pick up my new RTV-XG850; the trailer was much more stable and polite vs. the previous time I used it. However, that could have been caused by: the brand new tires I put on it, the addition of the Sumo springs on the front axle and/or fixing the wrong shackle configuration problem. Who knows.