Bouncing down concrete freeways

[FC Mike]

We have a 2013 20' Flying Cloud towing with a 2006 Dodge Dakota 4X4 w/4.7 v8 & Equalizer hitch. We have towed on sections of I-90 that are concrete panels with expansion joints. On some section there is a terrible bouncing setup between 50 - 65 mph. Once it start oscillating the only way to eliminate the rough ride is to slow to to less than 50 mph. After the first jouncing experience, I installed new upgraded rear shocks and adjusted the hitch to transfer more weight to the front of the truck. I didn't weigh the rig but the setup is level and tows well except on concrete road surfaces. FC Mike

[brad1]

I ran into this problem on I90 in Seattle. It was so unsettling that I now detour to avoid it.

[dznf0g]

Sometimes LESS WD will help.....different with every rig. Also more TW will help. Do you know all your detailed weights?

[OTRA15]

Welcome to the forum, Mike!

By adjusting the WD to increase the weight on the front axle of the truck, you have also thrown some of the weight to the rear of the single-axle trailer IMO, in effect putting more weight further away from the center of gravity of your rig. As Rich said, you might consider dialing the WD down. When we got our FC20 the dealer's shop foreman, very experienced with Airstreams, told us we could tow just fine without any WD. But we do use a basic Reese with 800-pound bars set fairly light.

Single-axle trailers tend to hobby-horse more easily IMO, so getting the weight distribution just right is important. As also suggested you might want to weigh your rig carefully, as the fresh water tank in the very rear can be a heavy pendulum-like "moment" very far away from the center of gravity, another possible factor here.

BTW did you know there is a thread here for our 20-footers? We have unique issues to deal with, and the community there is very helpful, including Safari 20' owners with lots of AS experience.

http://www.airforums.com/forums/f516...rs-127845.html

Good luck!

Peter

Originally Posted by FC Mike

We have a 2013 20' Flying Cloud towing with a 2006 Dodge Dakota 4X4 w/4.7 v8 & Equalizer hitch. We have towed on sections of I-90 that are concrete panels with expansion joints. On some section there is a terrible bouncing setup between 50 - 65 mph. Once it start oscillating the only way to eliminate the rough ride is to slow to to less than 50 mph. After the first jouncing experience, I installed new upgraded rear shocks and adjusted the hitch to transfer more weight to the front of the truck. I didn't weigh the rig but the setup is level and tows well except on concrete road surfaces. FC Mike

Originally Posted by dznf0g

Sometimes LESS WD will help.....different with every rig. Also more TW will help. Do you know all your detailed weights?

[Ray Eklund]

Were your Black, Grey and Fresh water tanks full, evenly divided or empty?

Although friends had a 25 foot Arctic Fox, their Black & Grey water tanks needed to be emptied. The front end of his 2000 Tundra was hopping down the asphalt in Wyoming, when catching the dips in the asphalt. His steering was impaired in the process of undulating...

Sounds like you already have the 'hitch cure', but your water situation was not brought up as an additional item to keep in mind.

[BAB]

Have had the same experience with both Airstreams. It IS very unnerving when this rhythm gets going and I've tried to lessen the effect by speed changes, adjusting weight distribution, you name it. It is a PITA, but fortunately goes away when you get away from the too-high expansion joints.

[J. Morgan]

I have built an opinion that a lot of people tighten their weight bars too much.


Superat stultitia.

[OTRA15]

Originally Posted by J. Morgan

I have built an opinion that a lot of people tighten their weight bars too much.


Superat stultitia.

Especially with single-axle trailers with lighter tongue weights IMO, where one of the main purposes of WD is to dampen the hobby horsing caused by harmonic oscillations due to the pavement expansion joints at certain speeds.

Actually to be more accurate probably, it is not the individual joints which are the problem, but the fact that each joint separates two flat planes which are not exactly co-planar. In other words, as you move from one FLAT section of pavement, across the expansion joint, you actually cross onto the next FLAT section of pavement which is at a slightly different angle, relative to the first.

Only slightly different, yes, but different nonetheless. Combine multiple crossing events like this at just the right speed, and the harmonics reinforce each other, including the actions/reactions of the shock absorbers and springs on BOTH the tow vehicle and trailer.

Like a big Rube Goldberg device!

[slowmover]

Originally Posted by J. Morgan

I have built an opinion that a lot of people tighten their weight bars too much.


Superat stultitia.

Thus the point of experimenting with different settings (scale readings). Any given rig will have a fairly narrow possible range. Once known it's far easier to work within that range to ameliorate the problem.

Same for TV tire pressure range. Won't know until verified and tested. My bias is that most run the road towing with improper TV tire pressure.

[SpletKay06]

What you dont want to see is the unnecessary amount of stress being applied to your trailer while this is going on. Yet people keep cranking there wd hitchs way too tight.

[J. Morgan]

I don't exactly remember the "right" way to adjust the weight bars, but having done it that way a couple a few times only to pull over and loosen the bars a few miles in, now days I shoot to tighten the jacks to the place that my combination feels, rides, and drives best.

For me and my combination this is with the bars a lot looser than doing it "by the book" would indicate.




Superat stultitia.

[dkottum]

Have had some rough experiences on those concrete segments, we have even pulled off to another out-of -the-way route. We had a 2006 Tundra and 20' FC with Equal-I-Zer hitch, our first Airstream and it had the worst setup for ride.

We have experimented and learned some things. Now with our tandem axle Airstream, half-ton pickup (front and rear axles same weight rating) and tapered round w.d. bars we get a good ride by setting them so the load on each truck axle is close to equal.

A large part of it is loading, we try to keep our Airstream loads with heavy gear (and full water tank) over the axles. I believe this reduces the amount of rocking motion. We load the truck similar way, heavy gear forward in the bed (or rear seat area), and very light behind its axle.