Hi all-I don't normally post here, but I've got a nagging question about trailering that I haven't been able to find anywhere. I found out I wasn't the only person dealing with this. I had a person going from a 1/2 ton to a 3/4 ton to try to eliminate it. We both checked hitch head angle, drawbar height, different WD Hitches, leveling with the truck and adjusting chain links on the WD hitch. It only happens on concrete roadways. The nose of the truck starts to bob up and down. the truck trailer seem to see-saw. It seems like the truck and trailer are doing an 'inchworm' move. My trailer/ hitch guy has heard of it, but no answer. Any help or thoughts here? I promised my friend I'd check into on here. Advise or thoughts are greatly appreciated. thank you!

hitch out of adjustment. you don't have enough weight on the front axle. try taking it up on link on the chain and try it again. it is called porpoising, look it up and it might even be in the FAQ's section on this page. or look it up on u tube under trailer porpoising.

it is caused by the cut lines in the highway because they are to close together

What you are experincing is known as 'porpoising' It is a harmonic action caused by length of pavement expansion joints or arcing in prefabricated bridge sections in relation to your TV axle to Trailer axles. When you come across such roads, simply adjust your speed faster or slower to negate the harmonic effects. You cannot get rid of that affect by any adjustment other than speed.

Mine does this a little bit on certain sections of roads, but without doubt it is easily controllable with a properly adjusted WD system.

My fifth wheel will do the same thing. Airbags and better shocks on the truck helped a lot.

Odd question on trailer pitching | Good Sam Community

babies_dadeo
Explorer
Sep 04, 2013
hbillsmith wrote:
I've been using an Anderson WDH for a little over a year now. It's design is slightly different than the other WDH's and as with anything, there are those that like it and some that don't. I used to get porpoising when I just used a single sway-bar, but with the Anderson chain/neoprene compression design, I never do now. Barring going out to get an Anderson, just adjusting your speed will usually handle it.

Yep x2 here. Even on ugly secondary roads in Southern sask my Andersen has done an admirable job of controlling it. I am not saying it never happens, it is just that the hitch allows the trailer to settle back down behind you. Greatly reduces the drama associated with porpoising.
The easy answer is slow down. Speed can be huge contributor to the effect.
campigloo
Explorer
Sep 04, 2013
Turtle n Peeps wrote:
A set of Bilsteins will help a bunch. And I mean a BUNCH.

I wanted to try Bilsteins. I have a ram2500 w/36' 9200# TT. The guy at Bilstein told me I didn't need to upgrade. Which shock did you use?
Lowsuv
Explorer
Sep 04, 2013
I have an "Air-Ride " Hitch .
It allows the trailer tongue to rest on an airbag , and move up freely .
The down motion of the tongue is softened by the airbag .
When I look in my rearview mirror the trailer is moving up and down within a few inch range and the ride in my pickup is greatly enhanced .
There are other brands .
Car_Guy
Explorer
Sep 04, 2013
I reread my O.P.I didn't mention it originally. The Porpoising occurs only on concrete, never on asphalt. My truck is leased, so no altering of suspension. Almost sounds like I'm mis-loading the truck or trailer possbily?
Jetta03
Explorer
Sep 03, 2013
Porpoising. I had something similar, went to stiffer spring bars for the the wdh and that fixed it. I think its a combination of not enough spring rate and damping at the rear of the truck.
hbillsmith
Explorer
Sep 03, 2013
I've been using an Anderson WDH for a little over a year now. It's design is slightly different than the other WDH's and as with anything, there are those that like it and some that don't. I used to get porpoising when I just used a single sway-bar, but with the Anderson chain/neoprene compression design, I never do now. Barring going out to get an Anderson, just adjusting your speed will usually handle it.
Peg_Leg
Explorer
Sep 03, 2013
I saw one setup that had 2 or 3 tubes on the trailers tongue. These were adjustable via some cranking screws on the top. Can't remember a whole lot about it but it was to limit rebound.

My method is to just slow down. South of Louisville on I-65 they did a good job of grinding on the concrete and smoothed out a large section. So they can fix it if they are forced too.
93Cobra2771
Explorer
Sep 03, 2013
As you see above, may causes/ways to fix the problem.

I experienced it with too much weight transferring - hit a bump in the back and as the back went down weight transferred to the front pretty strongly and the front went down.

Expansion joints can cause it.

To little weight transfer will simply cause the back to bounce. When the back goes down, the front goes up.

I good set of shocks will slow the oscillations.

Proper hitch setup will help as well.
Turtle_n_Peeps
Explorer
Sep 03, 2013
A set of Bilsteins will help a bunch. And I mean a BUNCH.
K_Charles
Explorer
Sep 03, 2013
Change the distance from your TV axle to your TT axle or change your speed.