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Old 06-26-2015, 10:18 PM   #1
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Road "Harmonic"Bounce

Hello all.

So we just took possession of a 2016 Jayflight 29BHDS today and towed it about 150 Miles home. This unit does have the upgraded MOR/ryde CRE/3000 suspension on the TT.

My tow vehicle is a 2013 F150 Ecoboost Supercrew with maxtow. The truck has the stock suspension and P275/65/R18 Goodyear Tires (which are NOT LT rated tires). Truck has under 30K miles on it.

We purchased the equal-i-zer hitch system on this unit, and it did tow much better 95% of the time than the rented RV's I have towed in the past with the cheaper chain link systems.

My main issue I am still facing is what I am going to call "harmonic" vibrations. This is very dependent on the road surface, its always occurring on fairly new concrete with seams that the truck/trailer run over. The truck and trailer combination seem to run over the seams at exactly the right sequence that a very severe bounce starts, enough that belts are all holding you in the seats. Slowing down does significantly improve the bounce, but does not eliminate it. Once the road surface changes slightly, its back to smooth sailing. This same exact thing happened when rental trailers of similar size, yet a different hitch system.

I am hoping someone here has some advice on how to solve this (if it can be solved), I am suspecting a tire upgrade to LT 10 ply tires on the truck might help (will gladly take recommendations on brand/model), or perhaps upgrading the shocks, but I really am hoping for some verification from people who have solved this before I go start replacing pieces 1 by 1 and sinking money in to the wrong fix.

Thanks.
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Old 06-26-2015, 11:14 PM   #2
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Quote:
Originally Posted by jsallman1 View Post
Hello all.

So we just took possession of a 2016 Jayflight 29BHDS today and towed it about 150 Miles home. This unit does have the upgraded MOR/ryde CRE/3000 suspension on the TT.

My tow vehicle is a 2013 F150 Ecoboost Supercrew with maxtow. The truck has the stock suspension and P275/65/R18 Goodyear Tires (which are NOT LT rated tires). Truck has under 30K miles on it.

We purchased the equal-i-zer hitch system on this unit, and it did tow much better 95% of the time than the rented RV's I have towed in the past with the cheaper chain link systems.

My main issue I am still facing is what I am going to call "harmonic" vibrations. This is very dependent on the road surface, its always occurring on fairly new concrete with seams that the truck/trailer run over. The truck and trailer combination seem to run over the seams at exactly the right sequence that a very severe bounce starts, enough that belts are all holding you in the seats. Slowing down does significantly improve the bounce, but does not eliminate it. Once the road surface changes slightly, its back to smooth sailing. This same exact thing happened when rental trailers of similar size, yet a different hitch system.

I am hoping someone here has some advice on how to solve this (if it can be solved), I am suspecting a tire upgrade to LT 10 ply tires on the truck might help (will gladly take recommendations on brand/model), or perhaps upgrading the shocks, but I really am hoping for some verification from people who have solved this before I go start replacing pieces 1 by 1 and sinking money in to the wrong fix.

Thanks.
Congratulations on the new trailer and welcome to the forum.

I know EXACTLY what you are describing. It is indeed a harmonic. I don't recall ever experiencing it when towing, however. There is a stretch of I-40 near Oklahoma City where I experience it. It has occurred every time with my truck, but has not occurred with any other of the other vehicles I've driven on that section of road. My truck experiences it with LT tires and with both new and old shock absorbers. In my case, however, I suspect it is 'frame flex' with my L-O-N-G vehicle and heavy diesel out front.

Have you driven that same road without a trailer? Did you still experience the harmonic?

You've effectively ruled out the trailer or the hitch as the cause. I think you are on the right track with different tires or shock absorbers. I suggest you begin with new shock absorbers. OEM shocks do not last very long and (IMO) are wimpy from day 1 and yours are pushing 30k miles. Even if new shocks don't cure the harmonic, you'd need them before long anyway. Take a look and do some research on the Bilstein and Rancho RS9000 (adjustable) shocks.

After that, I'd try increasing the air pressure in your TV and TT tires to at least the maximum on the sidewall. That would help simulate stiffer sidewall tires. Try that over the same road and see if that improves things.

I'm assuming of course that you know the TV tow and load capacity, the TT weights, and have the appropriate equal-i-zer hitch for your trailer. I'm fairly certain you will get some questions about those.

Good luck in getting this sorted out.
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Old 06-27-2015, 12:27 AM   #3
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I have experienced the same thing, but only on concrete, not on blacktop roads. It appears part of the problem is, most states can't pour a smooth road, each section is just slightly off from the previous and next section, hence the bounce. Changing speeds does help.
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Old 06-27-2015, 06:41 AM   #4
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I've once experienced what is described when towing an OP (Other Person's) trailer. Having done no real setup I just figured that it was related to tongue weight.

Even with a WDH it wouldn't hurt to get some real data at a CAT scale to get that one off the list.

As an aside, what has changed that they no longer seem to be able to pour and finish concrete roads to drive smoothly and last like the original Interstates? Newer concrete roads and re-poured bridge surfaces are not what they once were.

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Old 06-27-2015, 07:08 AM   #5
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I am thinking of installing shocks on my trailer to try and reduce the bouncing. You are correct it is only on specific concrete roads, and they almost always seem to be newer. I have tried to change my hitching setup, but nothing has really ever helped.
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Old 06-27-2015, 08:49 AM   #6
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Thank you all for the early comments and congratulations, cant wait to get this thing stocked and in use.

Yes, its definitely always concrete, and only smaller seconds of it, a few miles down the road it gets better. Blacktop and older highways have nearly no issues expect where you would expect to feel a good bounce (patched area etc). Have driven this particular stretch of road many times, US Highway 30 between Ames Iowa and Eastern Iowa, when driving with just the TV you feel the seems in the concrete but its very smooth and what I would consider "normal". Its definitely something related to having the trailer. When towing much smaller utility trailers (under 1500 lbs) with the same TV on the same road I notice nothing either of course thats a completely different beast weight wise. That trailer could be bouncing around and you would hardly even feel it in the TV.

One other thought I had last night after posting, the tongue weight of this unit is a little under 10% of the total weight from the manufacturer, and of course being new it was 100% dry and nearly 100% unloaded, so once we load it up towards the front I guess this could change a little. This is based all on weights from dealers, so keep that in mind. Getting it on scales after we load it up is not a bad idea at all as is checking pressures on everything, the truck tires cant go up much from where it is, they max at 44PSI, but I haven't dug into what the trailer is at yet.
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Old 06-27-2015, 01:23 PM   #7
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We have the same issue with certain stretches of concrete. Most other asphalt roads are smooth as can be. We have an Equalizer hitch too and when we first brought it home over a bumpy stretch of I-94 in WI, I called the dealer thinking maybe we had the wrong hitch or it was set up incorrectly. They said it was the correct hitch but would take a look. I decided to just experiment myself so I adjusted the hitch height, the amount of WD tension etc. several times. It made no difference on that bad stretch of road. I determined it was the road conditions and not my setup.

I did change the shocks on my truck to Bilstien 5100's (highly recommended). My original shocks had 80,000 miles on them and the shop that changed them out set they were still good but these new shocks dramatically improved the ride and handling. I changed the shocks more in the hopes of better stability in crosswinds since that was a real issue on our first long trip. These shocks do help some with stability in the wind, especially when being passed by big rigs, but only slightly helped with the harmonic bounce issue on concrete.

Enjoy the new TT!
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Old 06-27-2015, 04:17 PM   #8
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I would almost guarantee it was the road and not your setup. I just completed a 2100 mile round trip to Nashville. We hit a concrete section of I-81 and I-78 in Pennsylvania that would rattle loose the fillings in your teeth. I had to stay at 50mph and less for a good stretch on both roads.
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Old 06-27-2015, 06:05 PM   #9
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Before I saw your post, I had no idea others had experienced the same thing on different stretches of highway; I thought it was just my truck and the one highway.... WRONG!

So, after the responses I'm going to go out on a limb: It seems to me that even if you make changes and 'fix' your harmonic on '... US Highway 30 between Ames Iowa and Eastern Iowa...' your rig may someday encounter a harmonic on a different highway or a different speed.

I still suggest installing new and better quality shocks and increasing the air pressure in your tires. Those changes should make towing better on any road.
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Old 06-27-2015, 06:12 PM   #10
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Confirm weight distribution. After that just slow down. Try changing lanes. The truck lanes get pretty beat up. The truck drivers and the fifth wheelers don't notice this as much. Those of us with travel trailers have more of an issue. We are like a big long, but very flexible, beam supported on the ends by rubber tires. Maybe I will get around to inventing a damper in the hitch head one of these days.
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