camper sway question

[tnguy]

im lost on this one,,,  ive been towing for years and have had my share of "trailer waging" before but this ones got me, below is my set up, and this is what i have..

1, the camper sways WITHOUT the little trailer on it (and with it on)

2, camper has a "sway bar" on it

3, everything is tight and good (new tires on all 3)

at about 55-60 it does good for the most part (still sways sometimes) about 70 it does good and then bang it starts swaying if i speed up or slow down it quits, until i level off my speed then it will randomly start again... dont seem to be any "trigger" to start it doing it,

.


everything looks level and ive tried moving weight forwards and backwards in the camper with no luck...... any ideas would be great,,, thanks

 

[Frizlefrak]

OK, let me get this straight....

You're wondering why a single axle travel trailer (sometimes) pulling another trailer behind it sways at 70 mph?? 

I haven't the foggiest idea.  I will let the experts chime in. 

 

[Lou Schneider]

That's the difference between a bumper pull trailer and a 5th wheel.  The 5th wheel has it's hitch directly over the rear axle of the truck, so when the truck changes direction the trailer is pulled along with it, in the direction of the turn.

A conventional trailer has a lever between the truck's rear axle and the hitch pivot behind the rear bumper.  When the truck changes direction, the bumper hitch moves first towards the outside of the turn, then is pulled back into the turn to follow the truck.  That's a great way to set up sway.  You can mask this to some extent by adding a sway bar, which is just a friction brake that stiffens the hitch pivot so it takes more force to push the truck and trailer out of line.

Adding a second trailer only amplifies this effect, because you have another lever between the trailer's axle and it's rear bumper, pushing the rear of the first trailer back and forth.  When the first trailer starts to sway, the second is whipped back and forth - only twice as hard as the first trailer.

I'm surprised the combo is stable at 55-60.  Although even then, having a gust of wind hit you just right may be enough to get you in trouble

 

[tnguy]

OK, let me get this straight....

You're wondering why a single axle travel trailer (sometimes) pulling another trailer behind it sways at 70 mph?? 

I haven't the foggiest idea.  I will let the experts chime in.

ok thanks i will wait till somebody that knows what they are doing comes along...

 

[tnguy]

That's the difference between a bumper pull trailer and a 5th wheel.  The 5th wheel has it's hitch directly over the rear axle of the truck, so when the truck changes direction the trailer is pulled along with it, in the direction of the turn.

A conventional trailer has a lever between the truck's rear axle and the hitch pivot behind the rear bumper.  When the truck changes direction, the bumper hitch moves first towards the outside of the turn, then is pulled back into the turn to follow the truck.  That's a great way to set up sway.  You can mask this to some extent by adding a sway bar, which is just a friction brake that stiffens the hitch pivot so it takes more force to push the truck and trailer out of line.

Adding a second trailer only amplifies this effect, because you have another lever between the trailer's axle and it's rear bumper, pushing the rear of the first trailer back and forth.  When the first trailer starts to sway, the second is whipped back and forth - only twice as hard as the first trailer.

I'm surprised the combo is stable at 55-60.  Although even then, having a gust of wind hit you just right may be enough to get you in trouble

yes i understand the physics of it (ive pulled almost every type of trailer out there) AND i had this same setup before (just a newer camper) and it pulled great at any speed (unless operator error caused it lol)  this camper however (even pulled alone with sway bar) dont like to play nice   i thought the old "car tires" they had on it when i got it was the problem so i bought brand new 8 or 10 ply tires for it. no change,  thanks

 

[Gary RV_Wizard]

Trailer sway is basically caused by weight imbalance. That translates to insufficient tongue weight on the trailer, so that it fails to quickly follow the tow vehicle. Hooking the second trailer exacerbates this because the second trailer's tongue weight at the very rear of the first actually reduces the first trailers tongue weight (the teeter-totter effect).

A travel trailer should have 10-12% of its total weight on the tongue (ball hitch). In your case, 12% would be a good target, to help make sure that second trailer stays stable too. The second trailer also needs to have at least 10% tongue weight.  Shift some weight forward and your problems will cease.

Lastly, SLOW DOWN! 70 mph exceeds the the speed rating of the ST type tires on the trailers and contributes to the severity of the sway. ST (Special Trailer) tires are rated for a max of 65 mph.

 

[tnguy]

Lastly, SLOW DOWN! 70 mph exceeds the the speed rating of the ST type tires on the trailers and contributes to the severity of the sway. ST (Special Trailer) tires are rated for a max of 65 mph.

thanks, im going to try the weight on the front and see what happens, PROBLEM is...... the camper is mostly empty we only have the bare essentials in it, we like having a roof over our heads BUT like it simple   (i can see it now im going to have to carry sand bags on the tongue every time we go camping!! LOL )  the second trailer is just to haul firewood on and we usually only take  a little bit of wood with us and then use the trailer behind the truck to go "gather" more wood for the time we are there, and trailer usually comes home empty. thanks

 

[Gary RV_Wizard]

Sometimes an empty trailer is what causes insufficient tongue weight. However, it most cases it is a matter of where you put the weight, not how much.

Try it with a 80# sand bag draped over the tongue and see if it gets better. If it does, start figuring how to reconfigure your usual gear to achieve a similar distribution. Or maybe add a battery to the tongue, or a larger LP bottle to gain some useful weight up front.

Do you know your tongue weight now?  It might be low enough to weigh on a bathroom scale (300 lbs?). If not, there is a technique for using a scale and a lever to weigh it. See http://hildstrom.com/projects/tonguescale/index.html  Or just go to a scale and get it weighed for around $10.

 

[tnguy]

Sometimes an empty trailer is what causes insufficient tongue weight. However, it most cases it is a matter of where you put the weight, not how much.

Try it with a 80# sand bag draped over the tongue and see if it gets better. If it does, start figuring how to reconfigure your usual gear to achieve a similar distribution. Or maybe add a battery to the tongue, or a larger LP bottle to gain some useful weight up front.

Do you know your tongue weight now?  It might be low enough to weigh on a bathroom scale (300 lbs?). If not, there is a technique for using a scale and a lever to weigh it. See http://hildstrom.com/projects/tonguescale/index.html  Or just go to a scale and get it weighed for around $10.

thanks il try the sandbag, im not sure on the tongue weight,,,, before my surgery i could "sort of lift/bounce the tongue onto the ball if it wasnt lined up right (but i was 6'2" and 295# too

thanks

 

[OLDRACER]

How about your truck alignment?  Camper axle alignment?  Correct hitch ball, and hitch properly tightened?

 

[Frizlefrak]

Lastly, SLOW DOWN! 70 mph exceeds the the speed rating of the ST type tires on the trailers and contributes to the severity of the sway. ST (Special Trailer) tires are rated for a max of 65 mph.

If that were adhered to, 90% of the problem would likely go away. 

 

[tnguy]

How about your truck alignment?  Camper axle alignment?  Correct hitch ball, and hitch properly tightened?

truck was checked out not long ago and was good, camper has never been checked, ball and hitch are good

thanks

 

[tnguy]

If that were adhered to, 90% of the problem would likely go away.

no it dont ive pulled it a 55 before and it still does it, NOW that said,,,,,, speed does infact make it worse, but my problem with the whole thing is it shouldnt do it at any speed ..

thanks

 

[Big Bad Allis]

The others have given you a lot of good every day wisdom. Your set up will be difficult to eliminate the sway entirely. You have the shortest wheel base truck made + single axle travel trailer (tandems help some) and the small single axle trailer behind the TT.

Your speed with that set up was a recipe for disaster and illegal in some states.

Good Luck

 

[Mopar1973Man]

Lastly, SLOW DOWN! 70 mph exceeds the the speed rating of the ST type tires on the trailers and contributes to the severity of the sway. ST (Special Trailer) tires are rated for a max of 65 mph.

You might tone it down to 55-60 MPH while towing and you notice explosive tire failures disappear completely. Towing at 65 MPH is like towing at redline of the engine and your expecting the engine not to throw parts.

As for the sway issue I tend to agree with everyone. I would go out and scale the trailers and see where you land then you can figure where to put weight.

 

[ironrat]

What your doing is just completely wrong and unsafe for you and anyone around you. Slow down number one! You say you put wood in the back trailer, yea and wood is very heavy and is removing most of the tongue weigh you had with the front trailer. I would completely rethink your set up there. Two axle front trailer maybe and how much wood you really need with you and maybe carry it in the truck, either way you have a disaster waiting to happen there.

 

[tnguy]

What your doing is just completely wrong and unsafe for you and anyone around you. Slow down number one! You say you put wood in the back trailer, yea and wood is very heavy and is removing most of the tongue weigh you had with the front trailer. I would completely rethink your set up there. Two axle front trailer maybe and how much wood you really need with you and maybe carry it in the truck, either way you have a disaster waiting to happen there.

well i guess you have to argue your point with the state of Tennessee because they say its legal to pull doubles (of any kind) and 70mph is the legal speed limit....  NOW that said i understand where you (and others) are coming from with the safety part..... 

1, i dont carry but 100 or so pounds of wood on the back trailer and i balance the weight close to the axle (its mostly there so when we get to the camp i can use it behind the truck to go get more wood for the time we are there)

2, i dont drive 70mph ALL the time, and since ive been having trouble with it swaying ive only been running about 60-65 (and if it starts to sway i slow down more)

3,  when i say "sway" im talking about a few inches either way NOT whipping side to side taking up the whole lane (like ive seen others do)


despite what some may think i AM a safe driver and wont take chances that could hurt or kill somebody,,,,, that is why i was here trying to find out what might be causing the "sway" so i can fix it, i pay very close attention to everything i do when driving, the second i feel anything not right i slow down and start looking to see what it is, i dont even listen to the radio when im towing because i want to hear the tires/brakes/sway bar and anything else that "might" be making noise,,,,,, 


thanks for all the help and suggestions,,,,

 

[BobX2]

I would suggest leaving the second trailer at home, and hauling your 100 lbs. of fire wood in the front of your camper. Killing several birds with one stone that way, and I bet your sway issues would be gone. On another note, it doesn't matter what the speed limit sign says, that is the maximum allowable speed, not the speed you have to drive. As everyone else has been telling you, ST tires are rated for a max 65 mph, not whatever the speed limit might be. Slow down.

 

[Larry N.]

well i guess you have to argue your point with the state of Tennessee because they say its legal to pull doubles (of any kind) and 70mph is the legal speed limit....

Legal doesn't make it safe...

3,  when i say "sway" im talking about a few inches either way NOT whipping side to side taking up the whole lane (like ive seen others do)

If it's doing that, it's on the verge of "whipping side to side taking up the whole lane" -- just a minor additional disturbance, gust of wind, bump in the road, or perhaps a  second or two longer before slowing, might be enough to send it out of control, not to mention the stress you're putting on the hitch, the trailer and the tow vehicle. I had a trailer come straight at me a number of years ago, after detaching from its tow vehicle. I managed to avoid it, but it hit a vehicle behind me head on, causing serious injuries, and I went down an embankment in my avoidance maneuver, clipping a guard rail and just missing having it go through the middle of my car. I don't wish that on anyone.

The stress you're putting on that unit could cause something to break eventually, and then you'll have a loose trailer, or two in this case -- very ungood. Those hitches and attach points are not infinite in strength. We're talking lives, not just damage.