Fore and aft pitching

[mikeinca]

We got back last week from the first trip with our new 2017 25' FC and Ford F-150 Ecoboost equipped with an Equalizer 10K# hitch. In general the truck handled the FC well with good power in the situations I encountered (no really long high altitude pulls but some good grades) and stable handling and braking. The only thing I noticed is that on some undulating road services the truck pitched fore and aft.

What would cause this? Spring and shock issues? Maladjusted hitch? Truck too light? Or....? Thanks.

[cthornhill]

Wow...I have the same setup with the blue ox wdh. Got it last week and had the same experience. I've never pulled a trailer so assumed it was just the way it feels to pull 6500 lbs. Is you f150 the 4x4, as well?

[mikeinca]

Yeah, it's a 4x4 with the max towing package. I don't have much experience towing large trailers either so I was hoping to get some input on this.

[dkottum]

Too much weight in the back of the truck, too much weight in the front of the trailer, and/or not enough weight distribution. I've found this half-ton/mid-size Airstream combination needs 1400# w.d. bars. And they need to be tapered, flexible bars with the bars tilted down toward the back to keep the weight distribution fully effective as the roadway rises and falls.

[cwf]

Yup.. need to balance the "mass"... too much near the pivot (hitch) on truck or trailer will be difficult to keep the rig stable.

[mikeinca]

Originally Posted by dkottum

Too much weight in the back of the truck, too much weight in the front of the trailer, and/or not enough weight distribution. I've found this half-ton/mid-size Airstream combination needs 1400# w.d. bars. And they need to be tapered, flexible bars with the bars tilted down toward the back to keep the weight distribution fully effective as the roadway rises and falls.

Originally Posted by cwf

Yup.. need to balance the "mass"... too much near the pivot (hitch) on truck or trailer will be difficult to keep the rig stable.

I had my Weber Q, a Honda generator, a 1/2 full plastic jerry can of fuel, and a case of water in the bed of the truck and those were all situated at the front of the bed. Of course there was also the weight of the hitch itself at about 110 pounds. The trailer was running with full propane and fresh water tanks but empty grey and black tanks and no extra gear loaded in the front aside from normal kitchen ware and food stuffs. I tried to be careful not to have a weight imbalance. FWIW, I do have 2 6 volt batteries to replace the OEM setup which probably adds 50 lbs or so.

Maybe, as mentioned, it's the adjustment or capacity of the WDH. I may talk to my dealer.

[A W Warn]

Originally Posted by mikeinca

We got back last week from the first trip with our new 2017 25' FC and Ford F-150 Ecoboost equipped with an Equalizer 10K# hitch. In general the truck handled the FC well with good power in the situations I encountered (no really long high altitude pulls but some good grades) and stable handling and braking. The only thing I noticed is that on some undulating road services the truck pitched fore and aft.

What would cause this? Spring and shock issues? Maladjusted hitch? Truck too light? Or....? Thanks.

That undulating motion is more commonly referred to as porpoising (like a porpoise swimming motion). If you search online you will find a plethora of information.
I've found if the most common place it happens is on a concrete road where joints in the concrete set up a harmonic movement. But, occasionally one bump in the road can get it going it the vehicles are out of balance.

[Jammer]

To some extent it is unavoidable when the road surface is uneven. WD, shock, and loading problems can make it worse. There is, as far as I know, no way to completely eliminate it.

[ShinyPete]

Mikeinca-

My advice is....forget the dealer. No matter how good yours is, the person setting up your hitch probably eyeballed it at best and guessed at worse (perhaps without the rig loaded for travel) , and sent you on down the road. I've done 6+ setups for myself over the years and that many or more for RVing friends. It's not a big deal, and when done right can vastly improve your towing ride and performance.

AirForums' hitch area has some great reading regarding hitch setup, google your particular hitch model for detailed setup instructions, take an afternoon with hand tools and a tape measure, and setup the hitch from scratch yourself.

Also, run your tires on the F150 and Airstream at max inflation (cold), and be careful in loading what goes where as previously mentioned.

If you get your truck fender heights to where they need to be when hooked up and the rig level (and even better do some scale passes), you'll have a much better towing rig and a safer rig than many on the road.

Hope this helps.

[turk123]

Some of the suggestions here are good. You need to get involved yourself in the solution. As a good example of this, I'm new also to the airstream thing. We recently participated in a local rally and did not haul all that we usually take and the bed of my truck was empty. After spending much time "balancing" my rig last year with very good results, this trip I had porpoising. It was the opposite of a suggestion here. It looks like on the surface, too little weight on the tongue!

[featherbedder]

weight on tongue not balanced will also cause swaying of trailer.

[tjdonahoe]

My 4/4 ram goes straight , no up and down, better recheck everything..

[Mollysdad]

Originally Posted by Jammer

To some extent it is unavoidable when the road surface is uneven.

I agree. It's simple psychics. Your TV hits a bump and the trailer pushes you forward. Then the trailer hits the same bump and it jerks you back.
Now if you're on a smooth road and it's bucking, then I'd get worried.

[Wconley]

Originally Posted by Mollysdad

I agree. It's simple psychics. Your TV hits a bump and the trailer pushes you forward. Then the trailer hits the same bump and it jerks you back.
Now if you're on a smooth road and it's bucking, then I'd get worried.

I'm sure you ment "physics" but I love the typo. Sometimes it seems setting up trailer and tow vehicle is as much psychic as physics.

[uncle_bob]

Hi

Is there a nice stretch of road nearby that you notice the problem on? If so then most certainly do the adjust and check routine. Being able to do this or that and then check the result quickly is much more fun than waiting a week or two to see what happens.

Bob

[Rich Jenkins]

Hope you get it figured out.

I've minimized porpoising by:

Increasing the W/D amount on my hitch and

Redistributing mass inside the trailer. For example: I moved my (50A) power cable from the rear compartment to the fwd one one day. I could actually tell the trailer felt better.

Good luck. Lotta experienced guys here (I am not one) offering good advice.

[PKI]

Porpoising is the process of absorbing a road shock that was more than what the suspension would resist. The consequence of a strong enough suspension to resist the shock is the transfer of that shock to the coach and the TV. So, as the folks said, it is a matter of balance. Less mass in the ends results in less that the suspension has to control when the road undulates. A heavier tongue results in the need for more weight transfer and that results in a stiffer rig. That may help with the porpoising, but may also not be your objective as the AS likes a soft ride and I bet you do too. So, we come back to that balance concept. Enough weight transfer, but not too much. Enough suspension to absorb the shock and not transfer it. Those air bags can add both suspension and dampening. But the easiest solution might well be slowing to reduce the road impact some.

Hope to meet you down the road. Pat

[Mollysdad]

Originally Posted by Wconley

I'm sure you ment "physics" but I love the typo. Sometimes it seems setting up trailer and tow vehicle is as much psychic as physics.

What did I write?

[garen-kary]

When we traded up to a 28' from a 25' we got porpoising on our 145" wheelbase truck. Googled. Concluded we needed a longer truck. Added 18" to wheelbase and problem 90% gone.

[OTRA15]

Originally Posted by mikeinca

. . .
The only thing I noticed is that on some undulating road services the truck pitched fore and aft.
. . .

This can happen at certain speeds even with the right WD setup IMO. The harmonics are just too congruent for the hitch to dampen the action fully.

Next time this happens, try slowing down 10-15 MPH, or speeding up if possible, and see if the hobby-horsing gets better.

As others have said, changing the distribution of your loads can also help.

Probably a combination of various harmonic factors IMO. I would not assume that your WD hitch is at fault, although you could indeed try heavier bars, or a different tension/length on the chains as suggested.

Happy Trails!

Peter

PS -- Edit -- Good suggestion just now by JCWDCW about shocks being another factor.

PS2 -- mikeinca, how old are the shocks in your F-150, is it also a 2017 or older? Are you sure that your rig complies with all weight ratings, including the TV's rear gross axle weight rating. including the trailer tongue weight and all equipment in the bed? You might consider having your rig weighed all-around to be sure.