Community Forums

aubtc · 08-22-2016, 03:59 PM

I recently inherited a 35' DP from my parents and drove it three hours home with no issues. I replaced the tires and sway arm bushings. I loaded up my 16' car hauler with two ATVs and one SxS and took the family to an offroad park. The rig was extremely unstable and swaying badly. I tried moving the weight forward on the trailer (thinking it was a tail-wagging-the-dog situation) and that did not help. The trailer was high in the front so I leveled it with a 4" drop hitch. This too, did not help and it was all I could do to get the setup and family safely home going 45mph on back roads. I have towed this exact setup behind my older model Tundra with no issues except the one time I had the rides too far back on the trailer. The pickup does have after market airbags too keep it level due to the 600-700 lb tongue load. I am very familiar with towing but apparently clueless when it comes to dealing with a hitch on a MH that is mounted so far behind the rear axle. Am I applying too much tongue load? Do I need a WD hitch with sway control? Are the new Goodyear G661 HSA tires causing this? I attached a pic showing the final setup before the scary ride home. Any help is appreciated. Thanks

Gordon Dewald · 08-22-2016, 04:05 PM

I have no idea. From the picture it looks like a reasonable setup to my eye.

If I had to guess I would say that the weight on the hitch is making the front end of the coach a bit light.

You say 6 - 700 lbs hitch. What is the hitch rating? 5000/500?

YC1 · 08-22-2016, 04:44 PM

Definitely need to know the hitch rating but one or two sway bars for sure will help. I can't advise on the weight distribution hitch without more info on the rv and mfgr information.

aubtc · 08-22-2016, 07:02 PM

Hitch is rated 500/5000. Rv is 2003 National Tradewinds 7350 with cat engine on freightliner chassis. GVWR is 28,000 lbs with air ride suspension.

BFlinn181 · 08-22-2016, 08:37 PM

How much air pressure in the tires? If they are inflated to the maximum, it can effect handling. You should get the RV weighed, then look on the tire manufacturer's website for recommended PSI for the weight on the axles.

You might also try loading the trailer with less and see if that makes a difference.

Before you put new tires on, did the old ones show any wear patterns that could indicate an alignment issue?

aubtc · 08-22-2016, 10:16 PM

I really appreciate the responses. I am looking at getting the rig weighed and currently running 105 in the front and 100 in the rear per manufacturers sticker. The max tire rating is 110. I did notice that these pressures match the tire chart exactly for the max axle load that the rig is rated at for both the front and rear. So there is a good chance the tires are over inflated. The 10 year old Michelin tires showed no uneven wear with around 40,000 miles on them. When I first drove the rv with the original tires, all at 105 psi and no trailer attached, it drove really good at interstate speeds.

Gordon Dewald · 08-23-2016, 08:38 AM

I would certainly try weighing the coach and inflating the tires to the recommended pressures. I would also organize the trailer loading so the weight on the hitch is less than the 500 lb rating. Both are cheap solutions if they work.

Dennis_K · 08-23-2016, 09:52 AM

I would suggest investing in a tongue weight scale to make sure that is correct. I have a buddy who though he had his vehicle was positioned correctly for a 500 tongue weight and it "looked" okay but when the scale was used he had 1100lbs on it. I would also check for loose or broken parts. I have towed many thousands of miles with a similar diesel RV and never had any swaying, never used any type of anti-sway device either.

Crasher · 08-23-2016, 03:42 PM

If the air bags are inflated, it sure looks overloaded on the tongue. Too much weight on the hitch lightens the steer axle and compounds the problem with control. It's quite possible that the solution is in the tire psi and weight distribution. As mentioned, a cheap fix.

aubtc · 08-24-2016, 02:20 PM

Thanks for all the help. I am weighing the rig tomorrow and recreating the trailer load this weekend to check the tongue weight and redistributing the weight on the trailer. A friend of mine is also suggesting that one of the air ride level sensors could be defective and causing it to ride too tall. I found a level sensor bracket on the rear that was bent and plier marks showing that it was done on purpose by a previous owner. The direction of the bend would make the rear ride about an inch higher. Going to contact Freightliner to get the exact ride height it should be set too.

BFlinn181 · 08-24-2016, 03:07 PM

Ride height is critical, especially in the rear. With the short distance between the transmission and differential, ride height will effect the angle of the drive shaft and U joints.

The fact that lever was bent instead of releasing clamps on the rod ends and shortening or lengthening the rod shows it wasn't professionally done.

Gary RVRoamer · 08-25-2016, 06:14 PM

I'm very skeptical that a trailer that size could put enough weight on the hitch to lift the front end of a 35 ft coach appreciably. We are talking a 28,000 lb coach vs only 700 or so on the hitch. Nor do I believe that a weight-distributing hitch would help, though it certainly won't hurt.

Trailer sway is almost always a tongue weight issue - too little and the tail indeed wags the dog. Eyeballing it isn't very accurate, so scaled weights are need to figure out what is happening.

Other than "scary", it's not clear whether the coach was swaying around or the trailer was doing it. Was anybody behind you to see, or could you actually feel the coach moving around? Did the air suspension come up fully? Lack of air in the suspension can give some really scary handling.

jshupe · 08-25-2016, 07:48 PM

Quote:

Originally Posted by aubtc

I really appreciate the responses. I am looking at getting the rig weighed and currently running 105 in the front and 100 in the rear per manufacturers sticker. The max tire rating is 110. I did notice that these pressures match the tire chart exactly for the max axle load that the rig is rated at for both the front and rear. So there is a good chance the tires are over inflated. The 10 year old Michelin tires showed no uneven wear with around 40,000 miles on them. When I first drove the rv with the original tires, all at 105 psi and no trailer attached, it drove really good at interstate speeds.

Ten years old? I don't know that those are causing the issue, but they are undoubtedly an issue, regardless of how the tread looks.

Michelin is one of the few manufacturers that says it is safe to go over seven years, but even then, ten years is as long as you want to go with a tire.

BFlinn181 · 08-25-2016, 08:04 PM

Quote:

Originally Posted by jshupe

Ten years old? I don't know that those are causing the issue, but they are undoubtedly an issue, regardless of how the tread looks.

Michelin is one of the few manufacturers that says it is safe to go over seven years, but even then, ten years is as long as you want to go with a tire.

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.