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Old 04-14-2018, 09:17 AM   #1
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Porpoising

A friend of mine just bought a new trailer, (an SOB, alas). He's been trying it out with shorter trips of just a few hundred miles before he points the rig West for a weeks-long adventure.

He's asking me about "porpoising," which he's having trouble with, even though he has a high-quality (per comments here) W-D hitch.

Now, I've never had this problem, but he says it is disconcerting and is ruining the experience.

The W-D hitch was installed by the trailer dealer.

Now he wants to know what he can do.

Any recommendations?
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Old 04-14-2018, 09:40 AM   #2
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Lots of things can cause this. I would focus on the hitch setup. Making sure the WD bars are setup correctly would be something to check. Low tension on the bars can cause this to happen.
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Old 04-14-2018, 09:49 AM   #3
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Not knowing what his tow vehicle is I would say SLOW DOWN....

Many people when they first start towing assume they can go the same speed as they did without the trailer. Unfortunately they will see others towing way faster then is safe so they figure they can do the same. Kinda like the guy who passes you in the fog, maybe he'll be able to stop in time, maybe not.

Experience is the best teacher here, lets just hope it doesn't involve a collision.

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Old 04-14-2018, 09:56 AM   #4
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The angle of the hitch head, on some brands, is adjustable with the use of washers. A skilled hitch installer can fine tune this along with the correct size WD bars and chain tension. This is a skill that is acquired through training and experience.
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Old 04-14-2018, 10:17 AM   #5
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Agreed, the WD is likely off, which might have the front end too light.

For the sake of detail, what year and make of TV are we talking about? What type of hitch? An older TV might just need shocks. It’s more likely the WD set-up, but bad shocks can cause some excess movement.
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Old 04-14-2018, 10:40 AM   #6
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As others have said... check the weight distribution setup. Many dealers do not take time to install the hitch head at the correct angle and therefore the WD bars are actually doing very little and may be exacerbating the issue.

There are several threads about setting up WD hitches. Some of the details vary based on brand but the overall idea - to transfer weight back to the tow vehicle - is the same so basic principles apply to all.

One of the responses above mention shocks on the tow vehicle. That's certainly an item to check and it may be worth upgrading to heavy duty Bilstein's or something similar.

Also check the load distribution in the trailer. Weight centered over the axles is good. Weight on the front or back of the trailer may be contributing to the problem.
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Old 04-14-2018, 11:51 AM   #7
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So, if it is happening only when he is traveling across segmented concrete, then it is pretty common. If it is happening all the time, see above.

There are places, for example the Atchafalaya Viaduct, where the gaps between concrete segments are perfectly placed to set up a pronounced bounce that is self reinforcing so, at a steady speed, it just keeps getting worse. The best way to deal with it is to vary your speed up and down (on my rig, between 45 and 50 or so). This thrills the drivers behind you to no end...

Asphalt, even crappy asphalt, is your friend.
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Old 04-14-2018, 11:55 AM   #8
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My buddy has a brand-new F-150.

The SOB trailer is a 23-footer, or thereabouts.

The hitch is a Blue Ox Pro.
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Old 04-14-2018, 12:09 PM   #9
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The sway pro puts a bunch of bend into the bars. 3 1/2 links should be visible from the bar to the ratchet when it is hooked correctly. It takes some getting used to setting the arms. I have a breaker bar with a 1" socket to make it easier than with the "tool" Blue Ox provides. Also,the bars should be rated to the trailer. My bars are 1,000 pound bars and have 3 dots on the bar to identify that.
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Old 04-14-2018, 01:24 PM   #10
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I added a Safe Ride air hitch to my WD hitch. It cut down porposing by a whole lot. Bad shocks can also add to porposing.
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Old 04-14-2018, 01:27 PM   #11
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Thanks. I’ll ask what bars he uses.

I don’t have all the details, but if I recall correctly, he was ratcheting those bars big time, maybe only one link to go.

Does that suggest he might need heavier bars?
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Old 04-14-2018, 01:29 PM   #12
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One more on trailer loading — is tongue weight adequate?
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Old 04-14-2018, 01:48 PM   #13
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I use a Blue Ox SwayPro with 1,000# bars and found 1-1/2 links showing under the brackets is my rig's sweet spot. (11th link from the loose end of the chain in the slot). I had an uncomfortable bow push from passing big rigs and occasional porpoising on concrete highways before cranking the bars to the 11th link. Here is a picture of my rig set at the 11th link with three-pass scale tickets, plus a fourth pass showing 10 links (2-1/2 links showing) for comparison. http://www.airforums.com/forums/f42/...ml#post1985301 . I do have to extend my tongue jack really high to get the 11th link into the slot.

I would start by tightening the chains/bars one link at a time, re-leveling the trailer, test driving to a weight scale and re-weighing until you find the rigs sweet spot. A dealer can't dial in your WDH unless they weigh exactly the same as you, has your family (and dog) in the vehicle, loads the rig exactly like you do for camping, and spends all day repeating the above process of up and down a link until the sweet spot is found. I doubt many dealers will do this. Most dealers will do what mine did, set my hitch to 3-1/2 links showing, leveled the trailer and send me on my way porpoising down the highway with a white-knuckled bow push. I had to spend many days learning to dial in my hitch over multiple trips to find my sweet spot. And my sweet spot changed as I made changes to the loads in my rig. But I learned how to adjust my Blue Ox SwayPro and now have complete confidence in my rigs handling. Learning to adjust your WDH is similar to learning how to ride a bicycle, you don't do it perfectly on your first try.
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Old 04-14-2018, 06:01 PM   #14
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Quote:
Originally Posted by Dan and Liz View Post
One more on trailer loading — is tongue weight adequate?
I'm with Dan and Liz. How is the trailer loaded?
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