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Old 01-03-2006, 04:43 PM   #1
rickfox
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Join Date: Jan 2005
Location: Royse City
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M.O.C. #2959
A Herky-Jerky Ride

Good Evening All,

I have a desire to reduce the jerking and porpoising of my 3400RL 5th wheeler as I tow it down the road with my 2500HD TV. I have installed Firestone air bags to help me keep things level, but of course they do nothing to improve the jerking that occurs from time to time. I have heard tell about the Glide Ride and mor/ryde hitch pins, and air suspension hitches.

What do the great minds of MOC have to say about what I should buy!?
 
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Old 01-03-2006, 05:19 PM   #2
derfr
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M.O.C. #4953
Do you have shock absorbers on the trailer? If not, that will possibly be of the greatest help. The porpoising is caused by a rotation about the rear wheels of the trailer which leads to a slight forward and backward movement at the hitch which is felt as the porpoising and jerking. If you do have shocks, then someone else will have a better answer.
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Old 01-03-2006, 05:35 PM   #3
CountryGuy
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rickfox,

this has been discussed here a number of times, a search of the archives may prove very helpful.

many of us have added air hitches or pins, and feel they do help quite a bit, but that some of the worst roads, like I 10 and 20, I 94 near Battle Creek Michigan and others are so bad that there is nothing short of blasting the roads up and replacing will ever really do the trick.

good shocks on your truck will help as well. our OEM shocks were totally toast before 15000 miles on truck, replaced and the difference in ride in towing and solo is considerable.

some of the others will happen along soon and give your their ideas/opinions, I am sure.

good luck in your decision.
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Old 01-04-2006, 02:50 AM   #4
ken
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We also had that same problem with our Ford. We decided to replace the Reese 20K standard hitch with a new one. A Reese 18K Signature series was purchased with a slider since the new truck had a short bed. No more back forth motions. Reese has changed their clamp to a one piece clamp and the tolerance is much better between the 5th wheel and the Reese clamp. Nothing will help I-70.
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Old 01-04-2006, 03:29 AM   #5
ols1932
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We spent a lot and had Mor/Ryde axles installed, giving us individual suspension on each wheel on the rig. Additionally, we installed the Trailer Save hitch. Ride is superb. No porpoising, bucking, or pounding.
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Old 01-04-2006, 06:11 AM   #6
Dave e Victoria
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M.O.C. #635
Like Al & Carol said, there is a tone of stuff on this subject in the archives. In short, because of the geometry of the way a fifth wheel attaches to the Tow Vehicle any motion that affects the level pull ( ie trailer verticle motion or truck rotating about either axle ) will result in the pulsing motion you are referring to herky jerk.

The first thing to do is to make sure you have enough weight on the pin. It should be about 20% of total trailer weight.

The second thing is to make sure you are not overloading the trailer. Just crawl undr the trailer and note how much free movement there is above the axle. The more the better but at least an inch or two of movement. While under there make sure you have trailer shocks and that they don't appear to be leaking. I have come to believe this to be one of the most deficient areas in trailer design. As Orve said, independent suspension is the ultimate fix here. You will more than double the ability of the trailer to handle rough roads.

Third, the truck and trailer should ride close to level. You solved that with the airbags. And, as Al said, make sure the TV shocks (rear and front) are in good order.

Fourth, the Mor/ryde pin box (as well as others) directly attack the herky-jerk problem by putting an elastic element in the fore/aft connection at the pin. These work quite well, in my opinion. However, be advised that these have a limited amount of movement and eventually bottom out. Get on a really rough road and they will become overwhelmed just like any other system.

Finally, probably the cheapest solution is to change speed (usually slow down) and find a better road. This usually mean getting off the interstates. Heavy loads on these roads tend to get excited by the breaks in the concrete. Over time the traffic tends to enhance the undulations. These undulations are naturally at the natural frequencies of the vehicle suspension of the vehicles that cause them. These suspension frequencies are about the same on most heavy vehicles. Good shocks tend to raise the natural frequencies of your suspension and help you get away from the road frequencies. Here again, however, eventually the undulations in the highway get so large as to be able to overcome what ever you do until they resurface the highway.

I started to develop a model to describe all of this in concrete terms and will get back to it someday. Just too many other interesting things going on in the moment. (time for a homebrew)
Dave
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Old 01-04-2006, 08:07 AM   #7
Bighorn
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After researching all options to improve the jerking and bouncing, we installed firestone airbags on the truck and Demco's rocking pin box on the trailer. The air bags were first and they help with the bouncing but not the jerking. Then we installed the Demco glide ride pin box. http://www.glide-ride.com/ WOW what a difference.
The air ride 5th wheel hitch probably would have the same results but was twice the investment.
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Old 01-04-2006, 10:33 AM   #8
rickfox
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M.O.C. #2959
Thanks for all the info.

Bighorn, I have a several questions about the Glide Ride.

1) Was anything said to you about voiding the Monty frame warranty? When I asked my dealer about putting a different pin box on, he said that Keystone and the frame manufacturer would only continue the warranty if a Mor/Ryde box was used.

2) Does the Glide Ride require that the truck mounted hitch height be changed - for example did you have to lower the hitch mounting to compensate for the hitch pin being lower because of the added internal mechanism in the Glide Ride?

3) Did the resulting hitch pin extension change - for example, does the pin now stick out further from the trailer front, or is it now tucked further under, or is it essentially the same?
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Old 01-04-2006, 11:07 AM   #9
Dave e Victoria
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Rick,
I have the Mor/ryde and it works great. The idea behind it and the Glide Ride are essentially the same. Previously, I had an Air-Ride. It has some peculiarities of its own I didn't care for although it did seem to do a good job.. Personally, Ilike the rubber spring/damping system used in the Mor/Ryde.
Dave
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Old 01-04-2006, 02:59 PM   #10
Bighorn
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Rick.

Keystone is currently using A Lippert Pin box. The model on my Monty is #LIPP1116 rated to 19,000 lbs. Demco’s matched model #1116 and rated to 21,000 lbs. The overall construction is much better than the Lippert in my opinion. Heavier gage steel, clean powder coat finish and the bolt holes matched perfectly to the Montana frame.
I measured the original box in all direction using story poles and a transit for reference incase the new Demco box dimensions were different. The distance front to back was 3/16” shorter and the height was dead on. I can live with that. It took 45 minute to install torque and repaint the bolts.

This pin box is manufactured meeting Keystones specs. It is indeed an integral part of the overall construction but it is an added component to the frame. Under the Magnusson-moss warranty act the manufacturer would have to prove that the aftermarket part caused the frame to fail. After carefully inspecting the Demco Box, I feel comfortable that it shouldn’t cause any problems. At least I’m willing to take that chance. If the box fails due to my installation, well than I’m my own warranty station.

The biggest problem I had was the decal on the sides. It read ‘Demco Glide Ride Hitchhiker Exclusive’. It seems that all new Hitchhiker 5th wheels come standard with the Glide Ride. I called Demco and told them I can’t have a Hitchhiker logo on my Montana. They apologized and sent new decals with out the HH Logo.

Checkout the video on their website. It works exactly as shown.

Ed
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Old 01-04-2006, 04:27 PM   #11
rickfox
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Bighorn, I really appreciate the info.

You mentioned that it was 3/16" shorter. I take that to mean that the pin was tucked under the front cap of the trailer an additional 3/16", making any turning interference problems just a tad worse - although problably not enough more to make any difference. Is this correct?

I have 2 reasons I want to make sure I don't make things worse if I install a different pin box.

1) While I was doing my looking, one of the things I liked about the Montanas was that the pin projected out to the front of the front end cap, and supposedly you could even purchase an extended pin box. When my 06 3400RL showed up, the pin was tucked nicely behind the front end cap. In looking at other units already on the dealers lot I could see that some had extended pin boxes and some didn't. According to the dealer, all new units under 34' had the extended pin, those longer did not. I was told this was a requirement of the frame manufacturer. What a bummer. Now I have to be more careful since I am towing with a short bed TV.

2) When I hitched up to the new unit, it was clear that it had a lower profile that the Cardinal I had been towing. After lowering the truck hitch to its lowest position, the trailer front end still rides approximately 1.5" high. I do not want install a pin box that would make things worse.

I was tolk by the dealer that the Mor/Ryde pin box was extended but I have not yet been able to verify that. Any comments?
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Old 01-06-2006, 06:13 PM   #12
sreigle
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Rick, do you have the onboard compressor and in-cab control for the airbags? We adjust the psi in the bags when we hit pavement like that and it does make a major difference. Doesn't eliminate it but it does help. We do this without slowing. If no compressor then the solutions others suggest might be in order.

It sounds like you can't lower the hitch any further nor the pinbox. Sometimes adjusting the height of the hitch will help (shifts weight off the truck) or the reverse may help. But you probably wouldn't want to raise the nose any higher.

We also find this probably is nearly always only on interstates. Rarely have we had this problem on US and state highways. It has happened but it's rare.
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