Thursday, September 21, 2023


Trailer sway: Causes, cures, and getting away safe

New travel trailer users beware. A big boogieman lurking around the next curve could be your undoing. Trailer sway! The National Highway Transportation Safety Administration reports that about 50,000 trailer sway accidents are reported each year. And many of these are preventable. A bit of sway can ruin your whole day. What causes it? What can result from it? And what can you do to avoid the perils of trailer sway? Read on!

Watch that loading

One major cause of trailer sway is improper loading. Weight in any kind of trailer should be evenly distributed. Put too much weight on the rear of the trailer, the rear of the trailer can turn into the proverbial pendulum. And the trouble is, once that trailer begins to sway, things can get worse in a hurry—jackknifing your tow vehicle, maybe even rolling your whole combination over with disastrous results. Too much weight forward, you can actually pull the front tires of the tow vehicle away from the roadway, making for out-of-control steering and braking.

Avoid trailer sway issues due to improper loading. Ideally, 10 to 15 percent of your trailer’s gross vehicle weight should be on the trailer hitch. Got a 10,000-pound trailer? Then look to see 1,000 to 1,500 pounds on the hitch. How do you know if this is the case? Scale your loaded trailer, ideally knowing the weight on each tire, not just on each axle. When you know the weight of the trailer on its axles, the weight of the tow vehicle while hitched, then you need to unhitch the trailer. Now run the tow vehicle over the scale and weigh it by itself. Subtract the weight of the tow vehicle from your combined weight, then subtract the weight of the trailer tires (combined axle weight). The result is how much weight is resting on your hitch.

Trailer sway when the wind blows

trailer sway

Other causes of trailer sway happen when a big truck passes you. You soon feel that sinking feeling in your gut as your trailer wants to go with that truck. One or two sway bars between your two vehicles and your trailer can knock that problem out. Sway controls are friction control devices that reduce the amount of sway a trailer makes. They’re not expensive, and the average do-it-yourselfer can install them.

Adjusting a sway control isn’t difficult. In many cases, the “factory” adjusted point will work. But if you find too much sway, or too tight when turning, readjust the sway control tensioner a quarter turn “on” for tighter, or “off” for looser. Road test and repeat the adjustment as needed. One thing about sway controls, be sure to turn them “OFF” when you hit an area of wet pavement.

Other causes of trailer sway include tires that are below proper inflation. Check your tires cold every morning before heading out. Too much “foot in the pot,” as Grampa used to say, can also cause dangerous sway. Slow down! And here’s another time to really slow down—as in, park it and wait. Areas of high winds can really cause control problems. If high winds are forecast, beware. If you start to feel out of control, get off the road and wait it out. A 2009 study of commercial towing accidents showed that a 35-mile-per-hour crosswind can exert 3,440 pounds of force on the side of a large rig. You aren’t as big as a semi, but the point is still this—you are bigger than a passenger car, and the wind is bigger than you.

Coming away alive from trailer sway

trailer sway
Brake controller

What should you do if you encounter a case of trailer sway? First, keep your head. A possible inclination is to hit the brakes. Don’t! Get your foot off the accelerator but stay away from the brake pedal—unless you’re going to hit something. Instead, carefully apply the trailer brakes ONLY, by pushing the manual lever on your brake control. Practice this while parked so you know how to quickly find and apply the control. Stepping on the tow vehicle service brake is far more likely to really mess things up, but slowing the trailer and allowing it to bring your combination back into control may save your bacon.

There are a couple of interesting (terrifying?) clips of travel trailers that got into trouble when trailer sway overcame them. Watch it, and listen to the commentary. Don’t let yourself become a YouTube video. Prepare your rig, and yourself, to avoid the dangers of trailer sway.



  1. I have pulled a 34 foot travel trailer across the country several times and I have had several weight distribution hitches with built in sway control. They all worked ok. I still had to watch out for semi trucks and gusts of winds. My last hitch I bought was a ProPride 3P hitch and all sway went away. The hitch is a little pricey but what cost would you put on your family’s safety.

    • I second the ProPride. I bought one with my first travel trailer in 2009 and I have never experienced sway or any problems with semi trucks passing or cross winds. I had a blowout on a single axle trailer at 62 mph on an overpass and had to drive a quarter mile dragging the rim. I never felt any difference at the steering wheel. I simply slowed down and continued to drive until I could pull over at the junction with the entrance ramp. If the trailer had swayed it could have flipped over the guard rail and onto the road below, perhaps pulling the tow vehicle with it. At that moment it paid for itself. I changed the tire and went on my way. ProPride eliminates the possibility of sway.

  2. Once going downhill, a strong gust of wind hit us from the side & our rig went into a severe swaying motion across the road. Using the trailer brake control, forget about it. I do not think how well practiced, there will not be time to reach for it or use it in a panic situation. Maybe in a light sway, but not the kind when your rig is swaying across lanes of traffic. The only thing that saved us was the fact our trailer brake control leads our vehicle’s brakes. Holding the steering wheel straight, while the rig violently swayed back and forth, with just a very very lightly brake application. We rode it out, the trailer brakes helping slow us more than our vehicle brakes until straight.

  3. I’m having trouble following your math, or process. If I’m reading it correctly it boils down to:
    Combined Weight Minus Tow Vehicle Wt. Minus Trailer Wt.(unhitched) I must be reading wrong.
    Since I added 2 Ebikes on a hitch behind my trailer I’ve been looking at this pretty closely. I believe my hitch weight is low. I have to have Weight Distribution connected with the sway control attached.
    I have 3 scale tickets from our last outing. Hitched with out WD, hitched wo WD, and unhitched leaving the truck on the “driver” weigh pad and the trailer on the trailer weigh pad.
    GCVW is mysteriously different between hitched and unhitched, 40 lbs. I’ll lay out each scale ticket below. (1)

    • If I follow the process I seem to end up with 40 lbs which is ridiculous.
      Scale ticket 1 hitched with WD: Steer 3260, Drive 3480, Trlr 5880, Gross 12620
      Scale ticket 2 hitched no WD: 3000, 3860, 5760, Gross 12620
      Scale ticket 3 unhitched truck on Drive pad, 6240. Trlr on Trlr pad 6340, Gross 12580

      I actually took the time/effort to create a scale from Youtube pro’s. 5′ beam and bathroom scale. That calc = 546 including 5% for distance between jack and tongue. 12.5% target would be 792.5. So I’m roughly 250 lbs light! Given 6340 trlr wt. or 88 lbs light for 10% target.

      Combined Wt. 12620
      Minus Truck = 6380
      Minus Trlr = 40

      Where or what have I read/done wrong?


      • On ticket 1 your truck weighs 3260+3480-6720, and the trailer weighs 5880. On ticket 2 your truck weighs 3000+3860=6860, and the trailer weighs 5760, total combined weight the same both times. The WD hitch is distributing the weight to the front axle of the truck as it is designed to do. Unhitched the truck weighs 6240, so your tongue weight with the WD hitch is 480 pounds and without it is 620 pounds, or right at 10% of the trailer weight. You might want the tongue weight a little higher, but if it handles well (no sway) I’d say you are fine. Check my math, I’m not infallible.

        • What math did you use to get the tongue weight? Handling isn’t a sway so much as l would say a wobble. Especially when down grade. Expectedly. It would be really bad without the sway bar.
          Thanks for your input. I was hoping Russ (author) would chime in to explain how I got the math wrong. Hopefully you’ll share your math with me.
          I must have missed the notice when you replied. I did subscribe. Sorry for the late reply.

  4. Trailer sway is easily prevented; 1 don’t tow with the front of the trailer high in the front. If you can’t get it level then a slight front downward angle must be observed. 2 don’t load the trailer heavy in the rear. If you can’t equalize front to rear the heavy side should be toward the front. Most trailers locate the fresh water tank forward of the axle/s, don’t fill your tank full before a several hundred mile drive, wait until you are close to your destination to fill the tank, keep grey and black tanks empty when traveling, your tow vehicle and RV will thank you with better handling and better fuel economy, plus these tanks are suspended under the floor by strapping which could break.


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