3500HD pulling 26ft coachmen with a bit of trailer bounce

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trailriderjoe

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Joined
May 29, 2017
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Hello everyone,
Not new to towing or camping but new truck and trailer combo this season have me needing a little advice
Maiden voyage this past weekend went without incident but had a bit of trailer bounce, more than I like to see; not what I would call porpoising.
Can feel it a bit in the truck but nothing like the wave action others comment about.
Ran with only the twin curt sway controls not the WD hitch

Tow vehicle
2014 3500HD WT crew cab long box SRW 6.0L gasser
I like my trucks simple!
steer axle 4400 lbs
drive axle 3180

Trailer
2017 Coachmen 261RKS
Lippert frame
Dexter axles
Jaxxon ST20575R14 China junk (50 psi)
Speed rating M 81 mph - if you can believe that
1760 lb rating

Trailered weights
Steer axle 4060
Drive axle 4420
Trailer axle(s) 5220

Questioning three things:
1. Trailer tires - don't like China junk they put on from the factory.  Looking for any excuse to put a real set of tires tire on
2. Trailer shock kits - Not sure if the bounce is springs or tires...need to have a chase vehicle to help me verify this
3. WD hitch - Not sure how much I'm gonna being able to transfer to the front of a truck with a 14ft wheelbase

Thoughts?

Thanks in advance - Joe

http://img.photobucket.com/albums/v610/trailriderjoe/First%20trip%20rifle%20river%20spruce%20loop%202.jpg
 
dumb question for you - is the truck and trailer level? or the hitch high? you shouldnt have any issues with that combo unless its a weight distribution thing - try pulling it with out the bars too you will fine it rides better
 
No bars / WD hitch right now.
Tried this run with the just a 3" drop insert put the two level.
 
it almost sounds as if you don't have enough tongue weight ?. your truck is well within the towing range, and the trailer does not seem that long. when you couple them together, and not have enough tongue weight, it will make the trailers axle act like a pivot point, and cause the trailer hitch ball to pull your truck ball up, and push down , this is what it sounds like to me ?. then again, as you said, very well could be those china tires !. I just installed a set of 8-ply radials trailer tires on my 22ft camper, have not had it out yet ?..but not long from now !. will see how they ride ?. I also upgraded the whole suspension , axles from 2500 lb to 3500 lb axles, 1750 leaf springs, all new electric brakes, i'm sure it will give it a more ridged ride ?, but I am not riding in it, sooo ?..lol. maybe try hooking WDH up, and see how it rides/pulls then ?.
 
A WD hitch would put a good amount of that 900 lb. tongue weight on your steer axle and maybe 200-300 lbs. back on the trailer axles. Your pushing your hitch weight with 14.7%. This explains the bounce you feel. I'd get 1,200 lb. bars for that long span from ball to trailer axles.
 
Up until 2 years ago, I pulled at 27 ft. Forest River TT with a 2007 Chev 2500HD WT long bed.  TT measures 30ft from bumper to hitch ball. I initially towed the TT with just the WD hitch without the torsion bars attached as the trailer and truck were level and sway bars were not necessary. However, the bounce from the truck leaf springs was more than I liked with that arrangement so I attached the torsion bars and reset the hitch height. Setting the torsion bar drop to 3 links eased the bounce some, but did not eliminate it altogether. I think the actual tongue weight without the torsion bars really wasn't enough to load the rear springs so there was still some un-sprung weight on the truck's rear axle, if that makes sense.  Attaching the torsion bars and transferring some of that weight to the steer axle seemed to counteract the rear bounce. I don't have the scale weights handy but I remember the tongue weight percent after adjusting was 14% and the ride was tolerable.

I parked the TT on a lot and now tow a 5th wheel. Now dealing with "chucking" and trying to improve the ride.

Good Luck,
Reggie
 
You should probably weigh the trailer tongue. 

https://www.etrailer.com/faq-how-to-determine-trailer-tongue-weight.aspx
 
I looked at your truck and trailer ( I did not notice it earlier ), but it looks like your trailer is not level at the hitch point ?. and a dumb question, but is your fresh water tank in the rear ?, and full ?, close to full ?, if any water is in your fresh water tank, and it's behind the axles ?, this won't help your bouncing at all. deff try pulling with the WDH :).
 
Rene T said:
You should probably weigh the trailer tongue. If the numbers you provided are accurate, the tongue weight should be about 825 lbs.  10% of the trailers weight

https://www.etrailer.com/faq-how-to-determine-trailer-tongue-weight.aspx
Click to expand...
His scale weights listed allow tongue weight calculation. Difference of weight on TV is tongue (hitch) weight. He has no WD. See Cat Scale procedure.
 
If you look at my weights you will see that I have a little heavy on the tongue weight
total trailer is 6460#
tongue is 1240# (19%)
Little high but also remember when I hit the scales that day the rear kitchen was not fully loaded
And by the way I never travel with water in the fresh tank which is in the rear

regval
I have been thinking down your lines.
That 3500 has a lot of spring potential back there and I don't even come close to hitting the helpers when I don't have the dirt bikes and gear in the back.
The thing that bugs me is that the amount of trailer bounce I am seeing in the mirror can't all be coming from the truck.
There is a ratio between the front of the trailer to its axles versus what is behind the axle to the rear bumper of the trailer.
Let's crudely call it 3:1
That would mean if it was all from the truck leafs then the 6 inches at the rear bumper to the trailer would have to be 3 times that at the truck
Now what I am wondering is if you are right in that the truck starts it and the china tires and trailer springs exacerbate it.

I have 750# bars on the WD hitch right now.
Thinking about doing a little road trip to see if I can find a spot to throw some bounce close to home and them put the hitch on quick and try it again.

I'd bet that if I threw real tires on, a shock kit, and the WD hitch with any bars, the problem would go away.
That's not how this engineer's brain works.
belt and suspenders are nice, but which was the real problem?
 
I'd bet that if I threw real tires on, a shock kit, and the WD hitch with any bars, the problem would go away.
Click to expand...

A 3500 should be able to carry that 1900 lb tongue weight OK, but WD would help move some off the rear axle.  Not clear that would alter the bounce any, though. You could reduce the tongue weight by adding some water to the trailer fresh tank and see what effect that has. Cheaper to experiment than buying WD!

I don't see how tire quality would affect "bounce" at all, but you've already convinced yourself to change those so I won't belabor the point. Tire pressure might have an effect. Hard tires bounce more than soft  ones, but obviously you need enough psi to handle the tire load. Have you checked that?

I'm not clear on what is bouncing. You say it is not porpoising (and I would expect none with that much tongue weight), yet you say you feel it. And you see it in the mirrors? That sounds like shock absorbers would help. Most RV trailers would benefit from them, but only the higher end brands come with them from the factory.
 
trailriderjoe said:
If you look at my weights you will see that I have a little heavy on the tongue weight
total trailer is 6460#
tongue is 1240# (19%)
Little high but also remember when I hit the scales that day the rear kitchen was not fully loaded
And by the way I never travel with water in the fresh tank which is in the rear

regval
I have been thinking down your lines.
That 3500 has a lot of spring potential back there and I don't even come close to hitting the helpers when I don't have the dirt bikes and gear in the back.

The thing that bugs me is that the amount of trailer bounce I am seeing in the mirror can't all be coming from the truck.
There is a ratio between the front of the trailer to its axles versus what is behind the axle to the rear bumper of the trailer.
Let's crudely call it 3:1
That would mean if it was all from the truck leafs then the 6 inches at the rear bumper to the trailer would have to be 3 times that at the truck
Now what I am wondering is if you are right in that the truck starts it and the china tires and trailer springs exacerbate it.

I have 750# bars on the WD hitch right now.
Thinking about doing a little road trip to see if I can find a spot to throw some bounce close to home and them put the hitch on quick and try it again.

I'd bet that if I threw real tires on, a shock kit, and the WD hitch with any bars, the problem would go away.
That's not how this engineer's brain works.
belt and suspenders are nice, but which was the real problem?
Click to expand...
Tongue weight is the difference between total TV axle weight unhitched and total TV axle weight hitched with bars unloaded or no WD hitch. It is not just the difference of the drive axle weight. You have some weight from the front axle loading the rear axle without WD. Weight transfers from front to rear when suspension is not level. Etrailer page under commercial scale shows this. Your tongue weight is 900 lbs with the weights you provided.
 
Wireman is correct.

According to your weights, the truck without the TT weighs 4400 + 3180 = 7580#
The truck WITH  TT weighs 4060 + 4420 = 8480#

Hitch wt = 8480 - 7580 = 900#

TT axle wt is  5220

TT weight is 5220 + 900 = 6120#

Hitch wt / TT weight = 900 / 6120 = 14.7%

With all that said, your 3500 has more than sufficient capacity to handle that TT and that hitch wt.  In a recent thread, we decided you can not have too much hitch wt as long as it does not overload the tow vehicle.

My GUESS is that the truck is a stable platform.  The bounce is coming from the TT suspension.  I had a utility trailer once that could set up a side to side rhythmic bounce if carrying a balanced load.  If one side was heavier, it would dampen out any bounce.  The WD hitch may well be a good damper.  Upgraded camper suspension may also work well.

Good Luck!  Try the "free" fixes first!
 
Yea I definitely will be trying out the WD hitch next trip.  I have a set of 750# bars from the last trailer so it should be good enough to see if it helps dampen the bounce.
If not I will head for a shock kit.  Lippert makes a bolt on kit for my trailer.
Don't like the bolt on idea so much for the upper brackets so I might break out the welder...we'll see

Grashley & Wireman, you taught me something.
I was doing my tongue weight calc incorrectly.
I was forgetting to subtract off the weight transfer from the front axle to the back axle when the TT was hitched up.
That's why my numbers were a bit heavier tongue load.
The difference was the 340# that moved from the frt to the back truck axle.
I wrongly added that as tongue weight.

See...we all learn something new every day.
 
I have a 2012 2500HD Allison trans pulling a Coachman 31 ft TT.  I use the engine brake on 6 degree down slopes.

You are in for trouble with the tires.  I blew one finding out on way to TX coast.  The dealer (same Coachman unit on lot) said the Chinese tires are junk and told me to go across the street and buy 10 ply trailer tires (load range E I think).  The TT rides much better and I feel a whole lot safer.  These tires run at 70psi.

Now I am researching truck tires thinking of replacing mine with another tire.  Anyone with input on this would be appreciated.
 
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