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Bouncy Trailer

Cascadia

Cascadia

Undecided
Location
Orem, Utah
So about a month or 2 ago I go t a flatbed trailer to pull my jeep down to moab. It drove down and back great with no problems and was as smooth as can be. Then I got the 4 runner and towing it whenever I hit about 50 mph the trailer and truck start to get really bouncy...up and down, not side to side. So i figured something on my truck needed to be balanced. The tires were barely out on my truck. I then hauled the runner to Vernal to sell it and the same thing happened. Super bouncy around 50-65 mph(couldn't go any faster, too bouncy and scary). But then on the drive home I was pulling the trailer empty and it was once again as smooth as can be. What can I be doing wrong or is it not me. The tires are still the exact same as the beginning when I first pulled my jeep to Moab. It is an 8x14 flatbed tandem axle with 2 brand new tires the day before the Moab trip and 2 75% tires. I am now rigless but I would like to get it all sorted out before I pick up my next rig. Any ideas?
 
lewis

lewis

Fight Till You Die
Location
Hairyman
Could have something to do with placement. Too much or too little tongue weight. I have seen some crazy things with improper tongue weight.
 
Cascadia

Cascadia

Undecided
Location
Orem, Utah
Hopefully it's something like that. I know if it didn't have enough tongue weight I had some major sway side to side. That was a very uneasy feeling trapped between 2 semis in skinny lanes during construction. I got off the next exit and pulled it forward. After that is when the bouncy began and have not been able to control it ever since.
 
Caleb

Caleb

Well-Known Member
Location
Riverton
Could be tire ratings. If your tires are too low of a rating, you could get a bouncy feeling. Also, are you using a weight distribution hitch? If not, that will help tremendously. It could very well be as Lewis mentioned, not loaded properly will cause that as well.
 
L

LT.

Well-Known Member
Location
Los Alamos, New Mexico
What pressures are your trailer tires at? Also, the few times I have hauled on I-15 the trailer will start to bounce as you have stated. Perhaps you are getting some rhythmic isolation from the joints on the concrete highway at those speeds. Try inflating the trailer tires to max pressures, shifting the weight on the trailer and you may try to vary the speed some on the highway. Those joints on the Interstate may be to blame.

LT.
 
Cascadia

Cascadia

Undecided
Location
Orem, Utah
I wish the joints were to blame on the freeway. I know they are definitely to blame on university Ave. in Provo but it continues even when I'm not on the freeway (headed to little Moab) and back through Lehi. My trailer tires are at max psi. and I think they are rated at around 3300 lbs per tire and there are 4 of them so I'm fine there. It is just weird to me that it never happened towing a jeep but it always did with the 4 runner. I'm not using a weight distribution hitch but it has also not always been a problem. I feel like I loaded it the same judging by how much my truck sags.
 
L

LT.

Well-Known Member
Location
Los Alamos, New Mexico
I think what ChevyCrew was trying to describe is called porpoising. It is when the front of the trailer bobs up and down compressing the rear suspension on the truck. This causes a bouncing feeling on the truck and trailer. A common enough problem that air bags may help and a load distribution hitch may be able to take care of all together.

Another thought for you. I know that it is a tedious job but, it may be worth it. When you have the trailer on the truck next time take a measuring tape out with you and make sure everything is level. When you load the trailer the trailer suspension and the truck suspension is going to drop with the added weight. Re check all your measurements on the trailer and make sure that it dropped evenly on all four corners. Check the difference in drop at the hitch as well. You cannot make the assumption that the truck needs to drop the same amount as the spring rate on the truck will be different than the spring rate on the trailer. This may not fix the problem but it will give you a better idea as to where the problem really lies. I hope this makes sense to ya.

Another thought. If you can you may want to ask a friend if he would mind pulling your rig around the same areas as you are experiencing the problem. If so then I would say your problem is some where on the trailer. If not, then I would say that there maybe a problem with your tow rig. It does not need to be the same kind of tow rig anything would work as long as the trailer is close to level all the way around. Remember you want to have about 10% of your total weight as tongue weight. If your load is 7,000 lbs you will need 700 lbs on the hitch. Other than that I really don't have any other ideas for ya.

LT.
 
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Cascadia

Cascadia

Undecided
Location
Orem, Utah
That's good information LT. Once I have a motor back in my jeep I'll have to do that measuring method on all 4 corners. How do I know when I have 10% tongue weight? Thanks for the help so far. Hopefully I can figure it out with this info.
 
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