Community Forums

jshupe · 08-25-2016, 09:29 PM

Quote:

Originally Posted by BFlinn181

In the first post, OP said, " I replaced the tires and sway arm bushings." His response about the 10 year old Michelin tires was in response to my question about if the old tires showed any wear patterns.

Complete oversight on my behalf. My apologies.

msturtz · 08-26-2016, 01:45 PM

This is a very odd problem. Is this a Fred (front engine diesel) platform? What is the chassis model? It matters. From the picture you posted it appears that there is a very long rear overhang which is unusual for a DP rig because of where the engine is mounted. Usually the front wheels are set back from the front and the rear wheels are a similar distance back. A long rear overhang can create some instability due to the fulcrum position of the rear wheels. I.e. if the trailer is pushing on the ball toward the right it has a lot of leverage to push the front an equal distance toward the left. This can cause some concern in handling.

mackwrench · 08-26-2016, 02:48 PM

1st, trailer or not the ride height adjustment should be addressed. ...My $.02, once your certain Ride height is set correctly, I would be sure of trailer tongue weight. You describe a condition that's caused by not enough tongue weight.
The rear of MH will not "squat" if heavy loaded, just puts more air psi into air bags to level it. I can't see where that size load would change steer axle weight that much.
You may try another 1" or 2" drop hitch? It way take more than a few more pounds transfered ahead of trailer axles to make a difference.

Also make sure trailer leaf springs aren't broken, equalizer good etc....just to eliminate anything freaky at trailer side....

Mudfrog · 08-27-2016, 08:12 AM

The OP states the tongue weight is 600 to 700 lbs but then in another reply, states his hitch is rated for 500. I quickly read through the replies but didn't see much comment on that. If my math is correct, 600lbs is 20% over the max rating. Is it normal, and safe, to go this much over the ratings?

On the problem, I wouldn't think 600 lbs by itself would contribute that much to the tail wagging. But if the rear of the coach is loaded heavy, then i'd say there's a decent possibility the front has ended up a bit light. That long overhang would help to amplify the problem.

mackwrench · 08-27-2016, 10:52 AM

I'm suspect if it really has 700lbs on tongue... Plus OP stated ride height has bee tinkered with, he should correct ride height 1st...

Glenn and Kathy · 08-27-2016, 10:53 AM

Doesn't a drop hitch, which he said he added, also reduce the hitch weight to less than the original 500#. Sounds like his hitch is way overloaded.

Glenn

aubtc · 08-27-2016, 01:22 PM

Update. I'm really impressed by the amount of replies and help you guys are offering and much appreciated. Took off work this week to get the rv weighed, just to find out the local weigh station had been closed. I did call ahead but my calls had been forwarded to a station another hour away and they failed to mention that. I'm still convinced the tires are over inflated but can't adjust until weight is taken. The drive to the closed weigh station was much improved without the trailer behind me. So i will be weighing and adjusting the tongue weight to around 300 lbs and trying to center most of the mass directly over the trailer axles to lower the trailer moment of inertia. Whoever bent the rear ride height lever bracket did so because the linkage is non adjustable and the control valve cannot be rotated like most models. I have a list of the ride heights for this chassis and will adjust, but first I have to determine which axle I have. I am a mechanical engineer and have been really enjoying the challenge and learning process this rv has afforded me, but i do feel my coworkers, fiends, and wife will riot if I mention the word rv one more time, lol.

palehorse89 · 08-27-2016, 01:28 PM

Quote:

Originally Posted by aubtc

Update. I'm really impressed by the amount of replies and help you guys are offering and much appreciated. Took off work this week to get the rv weighed, just to find out the local weigh station had been closed. I did call ahead but my calls had been forwarded to a station another hour away and they failed to mention that. I'm still convinced the tires are over inflated but can't adjust until weight is taken. The drive to the closed weigh station was much improved without the trailer behind me. So i will be weighing and adjusting the tongue weight to around 300 lbs and trying to center most of the mass directly over the trailer axles to lower the trailer moment of inertia. Whoever bent the rear ride height lever bracket did so because the linkage is non adjustable and the control valve cannot be rotated like most models. I have a list of the ride heights for this chassis and will adjust, but first I have to determine which axle I have. I am a mechanical engineer and have been really enjoying the challenge and learning process this rv has afforded me, but i do feel my coworkers, fiends, and wife will riot if I mention the word rv one more time, lol.

As far as the trailer tongue weight, you also need to know the "Loaded" weight of the trailer..........tongue weight should be between 10-15% of the total weight to tow properly.

DAN L · 08-27-2016, 07:20 PM

Aubtc,
Are you using a hitch stabilizer such as the roadmaster?
It made a difference in my rig.

aubtc · 08-27-2016, 08:36 PM

I am trying to get the sway under control without the stabilizer the best I can and then probably add one anyways. I have an unused Stabil-izer hitch (weight distribution hitch with built in sway control) not being used, and am consisting using that too if needed. My dad had this rv before me and traveled all over pulling a custom built trailer with two trikes on it with zero issues and no sway device. He also had a low tongue weight. The trike engines were facing each other (back to back) and centered over the trailer axles and he claims it pulled fine.

DAN L · 08-27-2016, 09:45 PM

Aubtc,
I am talking about eliminating the slop between the receiver and the ball adapter. Drop hitch?
A little bit of slop here is amplified at the trailer.

aubtc · 08-28-2016, 02:07 AM

Never considered the receiver hitch slop would cause a problem, but on a drop hitch that is a very good point. I will definitely eliminate the play there. Big thanks!

Big_Boy · 08-30-2016, 09:46 AM

Quote:

Originally Posted by aubtc

Never considered the receiver hitch slop would cause a problem, but on a drop hitch that is a very good point. I will definitely eliminate the play there. Big thanks!

Blue Ox makes a very nice device ("Receiver Immobilizer") for eliminating slop at drop hitch mounting points. You may need two (2) of these and they are not cheap. However, they work quite well. See their website and look for part number BX88224.

You know, I think this whole idea of 'slop' at the hitch may be the root cause of your problems. You should look over the hitch platform carefully. A 5,000 / 500 lb hitch platform is pretty 'thin' anyway. Maybe this is flexing too much? I've had similar problems on a 2000 model year Suburban when trying to tow a load close to hitch rating. I bet you could replace this hitch platform for less than $150 and upgrade to a 10,000 lb / 1,000 lb platform.

The trailer axles could also contribute to this instability. There are good trailer shops that can check alignment of axles. If they are straight axles, they need to be checked as one may have a tire tracking off of true. A good old-fashioned trailer / truck alignment shop should still have the skills to bend the axle back into alignment.

aubtc · 09-06-2016, 12:48 PM

Had the loaded RV (minus trailer) weighed last week. Compared the axle weights to the tire manufactures load sheet and it states that my tires are approximately 25-30 psi overinflated. I currently run the manufacture's sticker rating of 105 front and 100 rear (these pressures assume both axles are at full capacity). The load table puts it around 75 for front and rear. Are other people running their rides with this low of a pressure versus the factory placard? I was thinking of going down to 80 or 85 psi to safely account for shift in weight due to fluctuations in tanks, ie. black, grey, fresh, and fuel.
On a previous issue, in order to adjust the suspension ride height, I first have to determine what suspension systems I have and use Freightliner's height chart to obtain the spec height. How do you figure out what type of suspension it is? The model numbers I am pulling off the axles do not correlate to the suspension chart.
As for the hitch slop, I have my own home machine shop and I am currently welding two large lug nuts to the side of the receiver and using modified wheel studs to tighten the hitch insert on the side. This should eliminate all hitch play. The hitch is rated 7000/700 and appears very stout, but Freightliner has placed a factory placard stating 5000/500. I am assuming the 5000 is due to the total braking capacity of the rv and the 500 pound hitch weight is due to the rear end being so far extended from the rear axle.
PS. Wife just called, new trailer tires arrived. Old ones were the cheapest tires I ever owned and came on the trailer new. They were wearing irregularly and I thought the axles were off, but turns out to be really pathetic tires. Some were up to 1/4" out of round brand new. I will not miss them. Thanks again for all the help.