What causes trailers to swing out of control?

[Raido Free America]

Too much tail weight behind the axle i believe.

Correct! there must be more weigh on the front, than the back, trailers aree designed to distribute the weight properly, if loaded evenly.

 

[RockHopper]

The one time this happened to me on the highway, was because I got distracted by the filly in the daisy dukes n cowboy boots that loaded my fill dirt.
She loaded it correctly, but the dirt was much too wet. When I hit the highway, the road vibration caused liquefaction and all 4-5 yds drifted back behind the axle.

Ya know...thinking back on her, I'd prolly still do it again. Whooeeeee!

 

[JEVapa]

Big girls loaded aft of the axles, like a fat chick roller coaster

 

[Snattlerake]

I have always had cars with hitches and some had very short wheel bases.
I found out decades ago too much weight towards the rear of the trailer will cause that wagging.

One friend had a large boat on a factory trailer that came with the boat that just would not stop the wagging and even adding dual axles did not solve it.

Moving the boat forward on the trailer solved it.
All my vehicles got heavier springs on the rear that were used for trailer pulling.

Lots of tongue weight.
I have built over 30 trailers and all of them got the axle set much farther back than your store bought trailers.

One customer that bought a trailer from me said he did not like the axle that far back.
He had not bought it yet though.
I told him I use my trailers and find many have the axle too far forward and pull terrible.

I told him I will give you all your money back if you do not like the way it pulls.
He called me a couple days later and said it was the best pulling trailer he ever owned no dog walking at all.

It is not that the trailer is light.View attachment 402176 I just built a very light trailer that you can pick up off the ground by yourself but it does not dog walk.
I pulled it empty to only 60 mph, swerved back and forth and it stuck to the ground like glue and tracked perfectly.
Axle is way far back on this one.

I fully expected you to come up with two shock absorbers attached to a swingarm on the hitch or something like that. Then you go and ruin it with sheer logic and physics.