How Much Rear Weight Causes Fishtailing ... ?

How about the other things in the camper? Load more to the front, check that the tongue is level or a little down, install a simple sway control, slow down.

 

I've always liked this video to demonstrate

 

Nowhere have you indicated that you've weighed your trailer loaded & ready to camp nor have you indicated that you've measured the trailer's gross tongue weight, loaded & ready to camp. Without knowing both of these numbers there's no way any one of here can definitively say what caused this sway you've experienced. Obviously you want to keep the trailer's GVW loaded & ready to camp within the trailer's GVWR and load it so the trailer's gross tongue weight (loaded & ready to camp) around 13% to 14% of that gross weight.

 

I would measure your tounge weight
https://www.etrailer.com/faq-how-to-determine-trailer-tongue-weight.aspx

Just need a bathroom scale that reads up to 400 or 500 pounds. (maybe even 350).

 

Sounds like you had too much loaded in the rear of the popup. Try shifting the weight around. You can also get a friction anti sway bar and you would need a new hitch receiver. I have one and have never experienced any sway with over 5k miles towing. I tow with a Pacifica minivan.

 

This explains how our posted speeds require tongue weight (center of gravity forward of the axle).
https://oppositelock.kinja.com/tow-me-down-1609112611

 

What could also cause sway is the tunnel effect that sometimes occurs if a big rig was to pass by you or you go through a valley between mountains. I have also had extremely bad roads where say your popup hit a pothole and want to go in a different direction. Sway is a very scary thing and a great reminder to always keep aware and to drive slower. Do weigh your full setup and get your actual tongue weight. Even the lightest thing could cause sway if you already are on the low end.

 

how fast were you going?

 

You could have a bad bushing in your leaf springs causing steering input! That could be unrelated to load. Inspect your suspension 100% before placing the blame just yet We had a jeep that did that to us once, dude tossed a bunch of steering parts into it before we notice the eye bolt moving inside the shackle when loaded... Good luck!

 

You got lucky. All the advice up above is right on. Do all those things. Especially the small sway bar. Additionally, if the trailor starts to sway, hit the manual break controller in the tv , and step on the gas. This will straighten out the camper.

 

My son (RIP) ran a moving business. He said he had a situation where the trailer (26' moving trailer) started swaying… he hit the button on the brake controller, and gassed the TV, and it straightened right out. Pretty much what Sjm9911 said.

To avoid such incidents in the first place, make sure the trailer is loaded properly with the proper tongue weight. If you have your manual, it will tell you what the proper tongue weight is. If not, 10% of the total trailer weight should get you in the ballpark.

 

No sway bar is needed. just do the weight distributing by moving heavy stuff to front toward tongue and light stuff in the rear. This will solve the swaying issues. I do the same with all 3 old popups and now Airstream. It is funny because many Airstream owners have WDH which includes sway control because they have not done weight distributing well. I keep mention it but only a few AS owner listen. There are a few AS owner not using WDH or Sway control equipment because they know the secret of solving swaying issues.

 

Thats all well and fine, but what about the 18 wheeler that passes you at 85 mph and creates a wind gust that starts your trailor swaying? Packing corectly is good, but it cant help with everything.

 

Like you said, that's what the brake controller is for.

 

I would rather have both for 40 bucks. Lol. Cheap insurance for me. It also depends on the trailor, some are know to sway , some aren't. Its up to you in the end. But i rather have the 40 $ bar and peice of mind.

 

Use Manual brakes and press gas pedal... using sway control and WDH actually does limit your turning although that was not the reason why I do not use them.

 

The sway bar they say cuts down on the turning radius, i never had to take it off to back it in. And never had it effect the turning. If anything it prevents rookie Jack knifing. I havent seen any wdh on pop ups.

 

I have the sway bar on my FnR. It drives me nuts. Finally realized it was why I had so much trouble backing the trailer into the driveway - I need to make a deeper angle than the anti-sway wants me to have. Took it off on the way home this last trip and was much happier the entire drive.

Now my FnR is a bit odd with its "no load hitch" - those castor tires under the tongue help prevent sway and provide a smoother ride than I've felt with other trailers. So, I'm not too concerned about dumping the sway system to make backing up and turning easier.

As said above, looking at your entire load and where it sits is the important thing. Also, consider the full weight of the trailer. A trailer with a loaded weight of 1500lbs should have a tongue weight between 150 and 225lbs. Additional food of 10-20lbs shouldn't be an issue. But if your loaded trailer is 900lbs, then 10-20lbs of food can definitely affect the 90-135lbs of tongue weight.

Speed, winds, vehicles passing, road conditions,etc., can all affect sway as well. And yes, your tow vehicle's steering system can make a difference also.