Why is it bouncing?

What does it mean when the trailer starts bouncing at 35 mph?
Is that just a bad stretch of road? On the interstate
Or something about the trailer or placement?

I slow down to 25, it stops bouncing, then slowly speed up and it starts bouncing again.


mvphoto74581.jpg

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Is it only on specific roads? Like older Interstate, or State routes? When I drove semi bunch of my co-
drivers & I figured out that 40 ft trailers were what put the Waves in most of the roads and around 60
mph those little trailers beat your brains out! Same piece of road with a 45 ft trailer stretched all
the way out would smooth out almost like you were standing still..
It shouldn't take much change in trailer hitch placement or moving trailer axles to smooth things out.
You might stop it by moving where the load is located too. Put a bit more weight on trailer tires and
less on truck tires.
 
I hope you didnt have to drive 25 all the way home ?? My
trailer will bounce but I can speed up And itll go away
 


It is hard to see that the trailer would bounce. Are you sure that it is not the rear of the truck/hitch of trailer?
 
(quoted from post at 08:22:58 05/02/21) What does it mean when the trailer starts bouncing at 35 mph?
Is that just a bad stretch of road? On the interstate
Or something about the trailer or placement?

Thanks for all the responses. I stopped a couple of times, tightened the chains, tried it again, and finally it stopped and rode fine.

I drove slow, 55 to 60, but it still felt like it bounced a lot when it hit a bumpy spot or bridge that had a low spot. I even stopped and bought a couple of tie down straps and added those.

It did tow fine, got home with no problems.

It's nice that you can rent a F-350, that will let you tow with it and a heavy-duty trailer for this type of very occasional need.
 
Usually you would center the rear axle of the tractor over the trailer axles. In that picture you were a bit front-heavy on the trailer which probably contributed to your problem.
 
Brother and I went to pick up a JD D last fall with his bumper hitch tandem axle trailer which was only a few years old. Trailer was bouncing
like crazy until got to about 50-60 mph then wasn't too bad. Had to go more than a 100 miles. Thought it would be OK with the
tractor weight on it. Well it was a little better but still bouncing like he11 at slow speeds, almost unbearable. After I got home
and had the tractor unloaded, I jacked the tandem axle trailer up and spun the tires. Both tires on one side had a belt separation
which was what was causing the bouncing. The tires probably had 95% + tread. Brother had both tires replaced. No more bouncing.
No warrantee since the tires came on the new trailer when he bought it. Don't remember the brand of tires.
 
You can drive a hiway in a car and think that its a great road....Then,you can take your loaded trailer out on the same road and it will bounce...It happens all the time to me
and my friends that load our tractors right..When I'm not pulling myself I ride to some pulls with my neighbor (pictured below) and we always see some bounce on certain
roads...
cvphoto87778.jpg
 
Its called slap your truck rides over a bump then a pause then the trailer pulls over it causing a back and forth slap , thats why semi driver seats slide back and forth to help not beat the driver to death
 

When my trailer is empty it has the same bouncing problem. My smallest tractor 3100# stops the bouncing.
Trailer bounced more than ever.
cvphoto88528.jpg

I discovered one 10 year old tire was coming apart. New tires helped a little.

I think the harmonic bouncing may be fixed with shock absorbers.

Weight on trailer solves my bouncing.

Try playing with air pressure. Reduce air pressure when not carrying max load. Monitor tire temperature with IR thermometer.
 
Geo, your trailer axles are slightly misaligned. One axle is going one way, the other axle is going in a slightly different direction. They get far enough apart and POP, the trailer bounces.

With the weight of the tractor it forces the tires to scrub. Probably why one of them was bulging.

That's why you test tow new tandem axle trailers before handing over any money. If it bounces, take it back and get a different one.
 
(quoted from post at 04:55:43 05/17/21) Geo, your trailer axles are slightly misaligned. One axle is going one way, the other axle is going in a slightly different direction. They get far enough apart and POP, the trailer bounces.

With the weight of the tractor it forces the tires to scrub. Probably why one of them was bulging.

That's why you test tow new tandem axle trailers before handing over any money. If it bounces, take it back and get a different one.


Barnyard, please tell how you made your measurements. The world needs to know!
 
(quoted from post at 08:00:32 05/17/21)
(quoted from post at 04:55:43 05/17/21) Geo, your trailer axles are slightly misaligned. One axle is going one way, the other axle is going in a slightly different direction. They get far enough apart and POP, the trailer bounces.

With the weight of the tractor it forces the tires to scrub. Probably why one of them was bulging.

That's why you test tow new tandem axle trailers before handing over any money. If it bounces, take it back and get a different one.

I can tell you how I do it. Take a SMALL cable, make a loop around the hitch, on a goose neck, and stretch it back to the axle on both outer sides in the exact same spots. I learned that way from the truck garage where I worked. They aligned semi axles that way.


Barnyard, please tell how you made your measurements. The world needs to know!
 
You may be right. I measured everything, It
checks out all good.
My 10k dump trailer works flawlessly at all
speeds.
I only have bouncing when empty around 35 mph. .
If I have to go a long distance empty, I reduce
air pressure and bouncing is also reduced.
 
I'm torn between comments made by Barnyard and Dr. Evil. I have multiple trailers and one of my tandem dual trailers
is also a hopper when empty. Kinda eliminates the load the tractor here or there comments. I was thinking about
Barnyard's theory of axle alinement and it really make sense. I like that idea. Dr Evil's comment of length of
trailer and axle spread or good too. I have a 35' Big Tex 12k with wide spread axles and that trailer pulls like a
dream. No hoppy or yanking. I know it has something to do with that distance between the truck wheels and trailer's
wheels in relationship to the bump in the road. Those two problems are completely different in my opinion.
 
In MI that is the norm for roads just have to live with it. I-69 from Lansing to Perry you can't hardly stay in the seat and I-94 around west of PawPaw is about the same in a semi. Most of MI unless they just layed it is that way. They can't seem to get a bridge and road at the same plain either.
 
next time weigh the truck and trailer loaded and get individual axle weights. You will get the smoothest ride with the weight equally divided between the trucks drive axle and the trailer, as long as the truck can carry that much weight. When its pounding like you feel every tiny imperfection in the road, put more weight on the trailer wheels. If its jerking you back and forth, put more weight on the truck.
 

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