Thursday, July 7, 2022


Trailer “tail-wagging” – Prevent this dangerous sway from happening to you

By Gail Marsh
What does a dog’s tail have to do with towing an RV? Turns out, a lot! Not knowing about the “wagging dog’s tail” can mean disaster. In fact, “the tail wagging the dog” syndrome is a main cause of trailer accidents today. Trailer tail-wagging is one of the reasons why many would-be RVers quit RVing after just one season.

Dog? Tail? What?

Imagine towing a travel trailer behind your truck. Think of the trailer as the “dog’s tail.” Your truck is the “dog.” Sometimes when traveling down the road, the travel trailer will begin to sway back and forth (also called fishtailing). This puts immense pressure on the rear end of the truck or tow vehicle. The side-to-side trailer movement can become so severe that the truck driver loses control. The trailer can flip, bringing the tow vehicle right along with it! Yipes! Even if the trailer doesn’t cause the tow vehicle to flip, the trailer can break free of the ball hitch and cause major damage to the trailer. Worse, the renegade trailer can potentially cause major damage – even death – to others on the highway.

Why does trailer “tail-wagging” happen?

“Fishtailing” or “tail-wagging” happens because in most cases the trailer far outweighs the tow vehicle’s weight. A travel trailer can weigh anywhere from 3,000 lbs. to more than 12,000 lbs. Compare that to your truck’s weight and you’ll see how the force of trailer sway can affect the truck driver’s ability to control the situation.

There are other factors that can contribute to trailer sway. Wind, for instance. A stiff crosswind can cause side-to-side trailer movement, as can the gust of wind that hits your rig when passed by a high-profile, fast-moving 18-wheeler.

Low tire pressure can cause the tire sidewalls to compress on the tow vehicle and/or trailer, too. Check tire pressure several times along your route to maintain maximum tire pressure, especially in the rear tires.

Improper loading or excessive weight can also cause “tail-wagging.” Pay special attention to the tongue weight on your trailer. The tongue weight should be no more than 15 percent of the total weight of the trailer. Don’t overload the back of the trailer, either. Too much weight can cause the trailer to “squat” and begin to sway.

Preventing trailer sway

Purchase special trailer sway bars or a sway hitch. Ask your local RV dealer for recommendations. Check product reviews online or ask other RVers what they’ve found to lessen or prevent trailer sway. There are several fine products specially designed to prevent, lessen, and/or eliminate “dog tail-wagging.”

There is one additional thing you can do to address the problem of trailer sway – and it’s free! Slow down. Many trailer tires are only rated for a maximum speed of 65 mph. Just because you’re allowed to travel faster in some states doesn’t mean you should – especially when towing a travel trailer. Slow down.

Watch this video to see a trailer “tail-wagging.” Yikes!

Stay safe out there! And don’t let the tail wag the dog!


The top 5 trailer towing mistakes owners make

RV Education 101 Online videos, including how to tow trailers, here.



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Archor Millis
5 months ago

I have a 5 th wheel camper 45 ft around 14000 lbs that at random it will start tail wagging it might be at 30mph or 70.
Tire pressures are all correct. Truck does not seat to low so any ideas

Gordy B
1 year ago

I cringe every time I see someone towing a trailer that is not reasonably level. the tongue should not be higher than level. There are so many “lifted” trucks running around towing trailers with drivers too cheap to buy a drop hitch to bring it level. That combined with excessive speed (all too common these days) can bring on wag at any time, an accident waiting to happen.

1 year ago

A Pro Pride hitch eliminates trailer sway completely. I had one on my 35′ 2016 Rockwood Windjammer towing with a 16′ F150 with the 3.5 EB engine. Towed thousands of miles, in the mountains and plains, in snow and 35 mph crosswinds with no sway and in complete control. They’re pretty costly, but what price can you put on the safety of you and your family?

1 year ago

When in this situation, a gentle application of the trailer brakes using the brake controller will generally tame the sway. Keep the hitch weight at no less than 15% of the trailer GW and don’t load your heavy gear in the back of the trailer.

Roy Kahl
1 year ago
Reply to  billh42

Absolutely, and can be fairly aggressive. You need to “pull” the trailer to straighten it. I have read several articles like this and applying the trailer brakes is seldom mentioned and should be the first thing. You should know where the manual apply lever is and be able to find it without looking.

Scott Ellis
1 year ago

*Insufficient*–not excessive–tongue weight causes sway. Excessive tongue weight may cause other issues, but sway will not be among them.

Wayne C
1 year ago
Reply to  Scott Ellis

I agree. “ The tongue weight should be no more than 15 percent of the total weight of the trailer” should read : The tongue weight should be no LESS than 15 percent of the total weight of the trailer. The only way for the tongue weight to be “excessive” is to exceed the hitch component ratings.

Bob p
6 months ago
Reply to  Wayne C

I believe the recommended hitch weight is 10-15% of trailer weight not a flat 15%. It should be no less than 10% with the truck and trailer level, the trailer can be slightly nose down but never nose up. In my personal hook up my truck is level but the trailer is nose down 1” from front to rear and i have no sway.

Wayne C
17 days ago
Reply to  Bob p

What ever percentage is preferred, the weight must be centered in front of the trailer axle. If it’s behind the axle, sway is assured.

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