porpoising

[Bzinky]

We are towing a Bullet 258 (55k empty 30') tt with a Ram 2500 6.7 Cummins diesel as our tv. We use an Andersen wdh. We originally had a Sierra 1500 as the tv and thought the porpoising may have been due to that tv. The Ram sure pulls much more efficiently but we are still experiencing what I feel is unacceptable bounce especially on concrete highways. We just returned from our first trip with this setup and while traveling Rt 27 near Montauk NY we thought our teeth were going to come loose. I have not actually taken any weight measurements but have tried many different positions and tensions with the Andersen. Any recommendations on setup or a better wdh? Would adding airbags help?

[notanlines]

Bzinky, first, welcome to the forum. You have a great plenty truck to tow that RV and no, air bags will not do the trick. I am more experienced with 5th wheels, but I believe you should start from scratch and take your rig across your friendly CAT scale. You will need to take three passes, one for $13.00 and 2 reweighs for $3.00 each. First pull up and put steer axle (front wheels) on the front concrete pad, your drive axle (rear wheels) on the second concrete pad and your RV axles on the third (last) concrete pad. Have that weighed and get your slip. Then remove your bars and tell them to weigh again. (another $3.00)
At that point, tow your RV to a handy dandy empty spot and return and just weigh your truck, steer on the first pad and drive on the second pad.
If you will, post those tickets for us to read and I can assure you there will be a minimum of four members here who can pinpoint your problem. I guarantee...

[flybouy]

As suggested visit the scales. Too little tounge weight can contribute to what you are describing. The tonmgue weight should be somewhere between 10-15% of the total trailer weight.

[Ken / Claudia]

My take may be different so I am up to listening to others. I have experienced both porpoising and bounce. Poster mentioned both.

Porpoising has happened to me with a full size truck in bed camper, pulling a large boat and driving into strong head winds. It feels like the front axle is to light as the front of the truck keeps going up and down. Slowing down until it stopped porpoising stopped all that. In my case it was a 1 time event. Dropping to 45 from 65 was the trick.
Bounce I get is due to the roadway empty or loaded driving over the same road the back of the truck bounces. Here it is the cement joints between the wore out cement surface that is the cause. I do not feel the bounce in my wifes small car nor the H3 at same speeds on same road.
So, just saying it may not be RV related.

[sourdough]

Like Ken mentioned, maybe it's the road surface and not the truck/trailer setup? You said your previous truck did it and now this one does it. Have you ever been over the problem road before when it didn't happen? "Porpoising" leads me to think a rhythmic type of undulation like concrete/asphalt joints. I've had what you describe happen to me a few times, to the point of literally felling like my teeth were coming loose as you describe. The worst was pulling with a 1/2 ton but I still felt it in a 3/4. Nearly always it's on a concrete highway. When it is happening have you looked at the highway to see if there are joints as you feel that porpoise motion?

[jasin1]

I hope you all can forgive me .. all I can think about when you mention porpoising ...”it’s not a porpoose”!

https://www.youtube.com/watch?v=DrzvLvVFBAU

[dutchmensport]

There is a country road near my home where the speed limit is 45 mph. No one ever drives 45 on this road, more like 60. I'm no exception... until one day.

Driving in the traditional SUV I never noticed anything unusual about this road. Oh, it seemed a little "bouncy" but it also has lots of slight dips in the road which made driving the road a lot of fun... especially at faster speeds.

Now one day I had the travel trailer in tow and turned on the same road accelerated to speed. 45 - 50 - 55 and then ... OH MY GOSH! The truck started bouncing up and down and the trailer hitch was actually banging on the asphalt road. I slowed way down and then realized WHY the speedlimit was posted at 45. At 45 I could safely tow. There was some roller coaster up-s and down's at 45, but nothing made contact with the road.

I think that is the reason for the porpousing? (however it's spelled). The road conditions get the truck and trailer into a rythem, cuasing the up and down pattern to the point it becomes near impossible to control. The only solution is to slow down.

That is different than hard hits at bridge transition joints. Those will just tear your truck and trailer up. You don't feel it in the family car, the suspension is just too soft. Attach a trailer and everything get's heavy. And the basic law of physics, the harder the object, the harder the hit! (or so it feels). Nothing gives... like in a softer suspension on the family car. Again, the only solution is to slow down.

[jasin1]

Could a problem with trailer tires or trailer suspension cause this? A broken belt in a tire or tire out of balance ? Proper air pressure ?Not sure of age of op’s trailer

[Gary Rivers]

My truck was bought used and the struts were well worn as well as the rear shocks. Replacing them helped to reduce this effect and made my setup more stable and reduced this effect.

[Bzinky]

Tt is a 2021. Tv is 2019. I did check tire pressure so I think I'm good there

[skids]

Everything “elastic” has natural resonance. Tires, metal frames, weight distribution bars, etc. There is a such thing as additive resonances (like 220 voltage). This is the purpose of shocks on the tow vehicle — to dampen the motion. The joints in the concrete may be at the interval where at a certain speed, it is causing the porpoising. Just a little theory here, no solutions.

[Ken / Claudia]

The easy test as suggested by 2 posts, drive on the same road in a passenger car/suv. I did a little research and found 1 company that makes balancing devices that go on each wheel to reduce rear end bouncing. But my opinion is they might work if it's the trucks problem. Not sure they would do a thing with a wore cement roadway.

[STLCG]

I had the same problem. I dropped the trailer tire pressure from 80 to 68 psi. That has helped a great deal. There are still spots were I have to slowdown but not many and I do not have to slow as much.

[travelin texans]

Originally Posted by STLCG

I had the same problem. I dropped the trailer tire pressure from 80 to 68 psi. That has helped a great deal. There are still spots were I have to slowdown but not many and I do not have to slow as much.

The issue with that solution is that you've created another one possibly causing more expensive issues than just a bad ride. By lowering the psi of your rv tires you've also reduced their load carrying rating by several hundred pounds increasing the risk of a blowout due under inflation.

[Ibdagriz]

Try a set of Timbrens on the truck. Really helped in pulling our 35' TT behind the F-250.

Griz

[JRTJH]

Originally Posted by STLCG

I had the same problem. I dropped the trailer tire pressure from 80 to 68 psi. That has helped a great deal. There are still spots were I have to slowdown but not many and I do not have to slow as much.

Originally Posted by travelin texans

The issue with that solution is that you've created another one possibly causing more expensive issues than just a bad ride. By lowering the psi of your rv tires you've also reduced their load carrying rating by several hundred pounds increasing the risk of a blowout due under inflation.

Sort of like saying, "I shot myself in the foot so my broken arm doesn't hurt any more".....

[Bamabox]

As you can see from my sig I’m towing a Cougar 21rbs with a 3500 Ram. I also have the Anderson wdh. It’s the only travel trailer I’ve ever owner, so I have no frame of reference with other hitches. I think the Anderson does an excellent job with sway, but I’ve never been totally convinced of the weight distribution part of the equation, because of the chains instead of bars. I sometimes get a little more bounce on concrete sections of interstates than I think I should. But the hitch is easy for DW and I to hook and unhook, and like I said I think it’s great at preventing sway.

[P&DZ]

I am also towing a Cougar 21RBSWE using a Anderson wdh but with a 1/2 ton. I was experiencing porpoising on uneven roads particularly over bumps. I put a bit more tension on the Anderson hitch chains and that has helped. I am also a bit light on the tongue weight at 740lbs when loaded at a 6,600lb TT weight, which may also be contributing to the problem.

[Northofu1]

When I had my TT and the 1500 Sierra I found that if I tightened up my Blue ox by one link and ran air bags at 30 psi there was no issue. It took some time to dial it in. I started at 20 psi, and 8 links. Went to 9 links and was better. Added 10 psi and was non existent.

My fresh water tank was at the front of the trailer and usually had around 10 gals.

[fstmvrerik]

I have a 39' Outback trailer and Anderson hitch. It took me a while after scaling the truck and trailer several times to figure out different configurations of water storage, and stuff in the trailer to get the tongue weight in the sweet spot. I also will tighten up the hitch when the tongue gets heavy and it really quiets the bouncing down.
I always keep my trailer and tow rig tires at the maximum recommended pressure.
You will see it recommended here and on most forums to keep the tongue weight between 10 to 15% of your trailer weight, and keeping the trailer level or slightly "nose" down. These factors will allow your suspension to do its job like it was designed and make for a better ride.

Having said that, some roads just will kick your butt, and you have to slow down.