Why is My Trailer Swaying?

[Delano1981]

I am having issues with trailer sway on with my Terry Resort 24 foot travel trailer, and I don't know why.
I pull it with a 2007 Ram 1500 5.7L Hemi 4X4. Trailer weighs 4720 lbs. unloaded. I just replaced the stock leaf springs with heavy duty springs from General Spring, and installed Bilstein 4600 shocks on the rear. The truck only squats 1 5/8" in the rear when the trailer is attached. There is no rise in the front at all with the trailer attached. As you can see in the attached pictures, the rig is riding level, but when I took it for a test drive without the weight distribution system attached, I experienced trailer sway going downhill on curves. The travel trailer was unloaded in this test. I have been pulling this trailer for years with this truck, but with weight distribution and have never had an issue. Since it is not squatting much now because of the heavy duty leaf springs, I thought weight distribution would not be necessary.

 

[CharlesinGA]

Many weight distribution hitches have anti-sway (damping) built into them. If you are intent on not using the WDH you need to install one or two friction sway dampers.

as you can see, they have a ball mount with arms that extend out one side or both sides with a small ball on it. The adjustable friction slider mounts to the trailer tongue and the small ball on the mount and has a lever to adjust the friction. Many people use one, some install one on either side. You have to loosen or remove them before backing.

The other issue is the trailer unloaded. A trailer needs 10% to 15% tongue weight to be stable, every trailer is different. Mine is very squirrelly below 13% tongue weight. You are possibly very light on the tongue being unloaded.

Another problem is now, its almost not possible to use a WDH with anti-sway properties as they depend on the bars being well loaded to have friction for the anti sway. Now, if you tension up the bars to where they work, you will have issues with the hitch wanting to lift the truck and trailer.

Charles

 

[Delano1981]

Thanks for the reply. I am not apposed to using the weight distribution system I have, it's a Husky Centerline system, and the trailer has towed very stable with that setup. I just didn't know if it was appropriate since the truck is already riding level.

 

[bigbAZ]

As a starting point and to eliminate guessing and trial and error the best approach is the three pass method at the CAT scales. At this point without those numbers you really don't know how much weight came off the front axle, or if you have the proper tongue weight.

 

[CharlesinGA]

And downhill in a curve is probably the worst possible situation, if you are gonna have sway that is it.

If you do try to use the WDH you are going to need to install it, and set it up from scratch according to the instructions. If the truck sits higher, the ball mount will need to be moved up the shank, and the bars and trailer frame brackets will have to be reset for proper tension.

Brian above is correct. Load the trailer and the truck for a trip, and make a trip across the Cat scales. First, truck alone, then truck and trailer. With those numbers you can determine if you have enough tongue weight.

Charles

 

[gwinger]

Those changes you made to the suspension is now causing the tires to make up the lack of cushioning in the suspension. The tire squat will cause the the trailer to porpoise up and down.
Especially if you are running the OEM type "P" rated tires.
I had that problem with my 1/2 ton Silverado Z71 with the HD suspension even with a WDH.
I replaced the truck tires with load range E. Problem solved.

 

[Kirk]

Trailer weighs 4720 lbs. unloaded.

Do you normally tow the trailer with it empty? As others have said, you need to get actual weights with the trailer loaded as you normally tow it.

I just replaced the stock leaf springs with heavy duty springs from General Spring, and installed Bilstein 4600 shocks on the rear.

I am wondering why you did this? If you had no sway before and now you do, the problem is most likely related to what you changed.

 

[gwinger]

Do you normally tow the trailer with it empty? As others have said, you need to get actual weights with the trailer loaded as you normally tow it.

I am wondering why you did this? If you had no sway before and now you do, the problem is most likely related to what you changed.

Like I said, replacing all that stuff and leaving the OEM tires on for a smoother ride puts the full load on the tires.

 

[Gary RV_Wizard]

Both your description of the changes made and the actual road experience indicate there is insufficient weight on the trailer tongue, i.e. at the hitch. RV travel trailers are designed to behave nicely with 10%-12% of the actual trailer weight on the hitch ball. That is determined by the trailer wheelbase, i.e. the distance between the ball coupler and the trailer axles. Too little weight makes sway likely, but a higher weight (more than 12%) is completely acceptable as long as it doesn't cause an overload on the tow vehicle rear suspension

Getting the truck perfectly level is nice for the truck but doing so at the expense of the trailer 90/10 balance is a no-no. Trailer sway is dangerous! You've beefed up the truck suspension so it ought to be able handle a lot of tongue weight without much effect on its own ride balance, And it doesn't have to be perfectly level either. Especially if you aren't using the WDH to help distribute the load.

Given your relatively light trailer and the beefed up truck suspension, you probably don't need the WD. And if you get the trailer balance in the proper range, you won't need sway control gadgets either. Basic physics will take care of it nicely.

Towing an empty travel trailer vs a loaded one can be problematic. It's the nature of a TT for most of the cargo load to be forward of the trailer axles and thus contribute heavily to the tongue weight. Without it, sway becomes much more likely. If you need to tow empty, it's wise to put some weight as far forward as practical, even if you have to carry some jugs of water or sand bags to do so. Even an extra 100 lbs far forward in the trailer can make a real difference.

 

[Mr Lars]

Ever pull an empty Tow Dolly? Talk about sway, you will feel it in the pulling vehicle. It feels like children jumping around in the back seat of a sedan.

 

[John From Detroit]

Many weight distribution hitches have anti-sway (damping) built into them. If you are intent on not using the WDH you need to install one or two friction sway dampers.

I am told that weight distribution in the trailer can affect sway however.. NOT SURE how that works.

I used to pull a scamp (Little 13' Polystyrene bubble of a trailer) and believe me it would "Scamp"er all over the lane if I hit oh say 50 MPH. Not fun to tow.

I added a friction bar as Charles in GA suggests (just one since it was an under 1 Ton Trailer) and tightened the screws... Tracked real nice after that. No tribble at all.

 

[DutchmenSport]

Trailer sway is caused by only one reason that I know of. It has very little to do with the tow vehicle, size, suspension, or anything. The thing that causes sway is the trailer tail being too heavy and the trailer tongue being too light.

And over loaded trailer with an under powered, under preforming tow vehicle will not cause trailer sway. The heavier trailer will cause the tow vehicle to squat, the axles to bottom out, the suspension to rock back and forth, and the tow vehicle to porpoise. But the trailer will ride steady.

 

[Gary RV_Wizard]

The friction bars are a crude way to dampen sway. It's much smarter to eliminate the sway at the source instead of trying to slow it down.

Plus the friction bars need careful adjustment of the friction so that it slows the sway but still allows turning. Need more friction as the trailer weight increases. Also need to readjust as the friction bar wears or gets coated with road grime. It's not s set it & forget kind of tool. Nor is it likely to be properly set when you get it back from the dealer.

 

[Delano1981]

Thank you for all of your replies and advice. I will load up the trailer and go to the scales and get all the weights and start from there.
Thanks again.

 

[Delano1981]

Ok,

I did some calculating with CAT scale numbers I have from a weigh I did when I first got the trailer. These numbers are all unloaded weights.

Truck Gross Weight: 5640 Lbs.
Gross Weight Combined: 10,860 Lbs.
Trailer Axle Weight: 4720 Lbs.
Actual Trailer Weight: 5220 Lbs.

Tongue Weight: 500 Lbs.
Desired Tongue Weight: 522 - 626 Lbs.

Based on these numbers, my unloaded tongue weight is 500 lbs, just under the desired 10 percent of 522 lbs. Plus, it looks like the new leaf springs have raised the hitched stance of the trailer slightly nose high by about an inch, so the combination of the too light tongue weight and the slightly high nose up attitude may be the problem. I'll load some weight in the front of the trailer and try it again.

 

[Lou Schneider]

I am told that weight distribution in the trailer can affect sway however.. NOT SURE how that works.

I used to pull a scamp (Little 13' Polystyrene bubble of a trailer) and believe me it would "Scamp"er all over the lane if I hit oh say 50 MPH. Not fun to tow.

I added a friction bar as Charles in GA suggests (just one since it was an under 1 Ton Trailer) and tightened the screws... Tracked real nice after that. No tribble at all.

The trailer's center of gravity has to stay forward of the axles, which translates into tongue weight. If the center of gravity including the rearward push by air resistance on the upper part of the front wall and suction on the back wall pushes the center of gravity behind the axle the trailer will sway.

This is demonstrated dramatically by a video produced almost 10 years ago by U-haul showing a car and trailer on a treadmill and what happens when the center of gravity goes too far to the rear, Nice and stable with the weight forward, self amplifying sway when the C of G is behind the trailer's axle.

 

[gwinger]

One other thing about the friction sway control. You should remove it before backing up! A tight turn while backing can jam the device or even pull it apart.

 

[Lou Schneider]

One other thing about the friction sway control. You should remove it before backing up! A tight turn while backing can jam the device or even pull it apart.

And back off the friction adjustment on slippery roads. It opposes movement in both directions and can lock the car and trailer into a permanent turn if the car's rear axle loses traction.

Cam type sway controls oppose movement away from a straight line and aid the combo returning to a straight line.

 

[Kirk]

Cam type sway controls oppose movement away from a straight line and aid the combo returning to a straight line.

But they only work with weight distributing hitches. Many of the lightweight trailers have warranties that are violated by use of a weight distributing hitch. If there is an alternative to the friction antisway device for them, I am not aware of it and I can tell you from many years of towing such trailers that the friction antisway does help with such trailers. They may not be great, but they are sometimes the best (or only) option.

 

[gwinger]

But they only work with weight distributing hitches. Many of the lightweight trailers have warranties that are violated by use of a weight distributing hitch. If there is an alternative to the friction antisway device for them, I am not aware of it and I can tell you from many years of towing such trailers that the friction antisway does help with such trailers. They may not be great, but they are sometimes the best (or only) option.

I don't understand why a WDH would void the trailer warranty. What if you just use the hitch without the bars? That way you can use the friction control since the pin for it is on the ball mount.
I know a lot of the smaller SUV's forbid a WDH since there is no full frame them.