What causes trailers to swing out of control?

[Cowcatcher]

That makes a lot of sense!

I will add that one of the trailers I saw do this at highway speeds was totally empty. It was a large double axle car hauler type flat trailer.

Do you remember what the tow vehicle was? Was the vehicle tracking straight?

 

[Ready_fire_aim]

That makes a lot of sense!

Do you remember what the tow vehicle was? Was the vehicle tracking straight?

It was an older lifted F250. The section of highway was 3 lanes and I was not directly behind him, so I couldn’t see if his truck was crab walking or anything like that. He slammed on his brakes and got it back under control relatively quickly.

The other one went way out of control! It was a heavily loaded single axle utility trailer. And it was kinda junky.. Possibly home made.

 

[Mr.Glock]

There is a lot of those lifted trucks that had the geometry in the suspension, axle angle etc not installed correctly. And damn do they do some wild ****! Scary ****!

Trailer:
To light or heavy in the ass.
To light or to heavy on tounge.
Both will bite your ass.

 

[Camo]

Rule of thumb is 10-15 percent tongue weight minimum. Too far back and it wags like a dogs tail.

 

[retrieverman]

In all the instances I’ve seen where the trailer started weaving, the trailer was too big or loaded too heavy for the tow vehicle. Off the top of my head, most wrecks I’ve seen caused by out of control trailers were being pulled by a Tahoe or Suburban.

 

[Camo]

In all the instances I’ve seen where the trailer started weaving, the trailer was too big or loaded too heavy for the tow vehicle. Off the top of my head, most wrecks I’ve seen caused by out of control trailers were being pulled by a Tahoe or Suburban.

Any short wheel base vehicle can get squirrelly quickly with a poorly distributed load.

 

[rickm]

I watched a 1/2 ton truck with a 16ft trailor loaded with square bales of hay go down a steep roadway and lost it just before getting to the bottom, had to much speed for the down hill with to much weight and trailor tried to over take the truck.

 

[RockHopper]

Think of it this way....

When the load weight isn't distributed over the load bearing axle, what you get is a pendulum.

 

[swampratt]

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.

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.

 

[turkeyrun]

#1 cause, loose nut behind the wheel.

#2 cause, improper loading, balance, and/or excess speed.