Trailer Braking, Trailer Sway & Windy Conditions

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March 30, 2009

I received an email from a reader the other day who was involved in a bad accident while towing a trailer 5 years ago. The accident was a result of a sudden wind shear, causing the trailer to start swaying out of control. The truck and trailer rolled over. Fortunately everybody was okay!

After detailing the accident, Mary who was driving at the time, asked me if I had any hints or tips to offer on trailer brakes, controlling sway, and what to do when you experience something like wind shear, cross winds, or towing in windy conditions. After reading Mary’s email I thought it would be an appropriate topic for an article.

Let me begin by saying that the safest measure for traveling by RV in windy conditions is not to travel at all. RV’s have a great deal of mass (length, width & height) and when that mass is confronted with strong wind gusts, crosswinds and/or wind shear the results can be devastating.

Sometimes the weather forecast can warn us that windy conditions are expected. These are the days that you need to make a conscious decision to stay put at the campground, or wherever you might be, and not take a chance traveling by RV. Trust me when I say it’s not worth the risk involved.

On the other hand what do you do when you are traveling on a fairly calm day and suddenly you are hit by a strong wind gust or crosswind? If you’ve been traveling by RV for awhile, either motorized or towable, you have probably experienced the forces of wind against the RV at one time or another. Possibly the most common occurrence is when a transfer truck passes you from the rear. I refer to this as the push, pull effect. The force of the air pressure coming off of the truck as it begins to pass pushes against the side of the RV and as it completes the pass it pulls you back in again. If you are not aware of the truck passing you, or if you are towing a trailer and don’t have some type of sway control this air pressure can cause the trailer to start swaying. The same dynamic occurs when a sudden wind gust hits the side of the RV unexpectedly.

The forces of air pressure are not the only thing that will cause a trailer to sway. Sway becomes an automatic factor with travel trailers simply because of how the trailer is hitched to the tow vehicle. The good news is that even though the potential for trailer sway is there, it can be controlled. Let’s look at some of the causes for trailer sway.

First and foremost poor trailer design contributes to trailer sway. When there is too much weight behind the trailers axles causing the tongue weight to be less than 10% of the trailers weight it has a natural tendency to sway.

*Incorrect tire inflation.
*Improper weight distribution hitch adjustments.
*No sway control on the trailer.
*A transfer truck passing from the rear of the trailer.
*Descending inclines
*Towing speeds and hitch weight
*Tow vehicle not properly matched for the trailer.
*Improper loading, overloading and poor weight distribution.

So, what can you do about it when it happens to you?

Most of these causes for trailer sway have quick and easy fixes. For starters, before you purchase a travel trailer, do your homework on the trailer. A poorly designed trailer will never handle well. Find a trailer with a tongue weight that is 10 to 15 percent of the trailers weight and match it with a tow vehicle that is capable of handling the load.

It is safe to say that with a well designed trailer, the proper tow vehicle, correct tire pressure, correct hitch adjustments, sway control and a properly loaded trailer we can control a great deal of potential trailer sway. That narrows the potential for sway down to what you could encounter at any given moment, even with a stable trailer; strong crosswinds, transfer trucks passing from the rear, bad driving conditions and descending steep inclines. Any one of these conditions will tend to push the trailer and tow vehicle sideways, but when equipped with the proper type of sway control and brakes, you can make normal steering corrections.

If the trailer become unstable and attempted steering corrections don’t control it you can use the manual override on the electronic brake control to regain control of the trailer. Slide the manual lever over slowly and allow the trailer brakes to engage and the sway control to put the trailer back on a straight course. If trailer sway becomes severe, reduce your speed gradually, avoid using the vehicle brakes if possible and manually apply more trailer brakes.

The brakes on the tow vehicle and trailer are a critical element to safe towing. Electric brake controllers are an essential component to safe trailer towing. The brake controller is installed inside the tow vehicle and supplies the power from the tow vehicle to the trailer’s electric brakes. There are two types of electric brake controllers, time delay activated and inertia activated. Time delay or solid-state controllers apply gradual voltage to the trailer brakes using a time delay circuit. A pendulum circuit that applies gradual voltage to the trailer’s brakes activates inertia or pendulum type controllers.

Both types of brake controllers allow you to adjust the amount of braking power and they both have manual overrides that can be used to activate the trailer brakes without using the vehicle brakes. The override feature can be used when descending an incline, to assist in slowing down and to prevent premature brake wear on the tow vehicle. It is also helpful in regaining control if the trailer begins to sway or fishtail. Always check the operation of the brake controller and trailer brakes before leaving on a trip.

*Have your trailer brakes, bearings and other components inspected at least once annually by a professional.

*Allow more distance for stopping then you are accustomed to. Do not follow other vehicles too closely.

*Do not use the tow vehicles brakes to control excessive trailer sway. This will usually make it worse. Manually apply the trailer brakes to regain control.

*When descending a steep incline, if it feels like the trailer is pushing the tow vehicle, reduce speed, down shift to a lower gear and use the manual override on the brake control to slow the trailer. Heavy use of the tow vehicle brakes can cause them to overheat and begin to fade.

*Always be prepared to slow down and try to avoid making sudden stops.

Passing Vehicles
*Allow more time for acceleration when planning to pass somebody. It may be necessary to shift out of overdrive for increased acceleration.

*Only attempt to pass a vehicle on a level road surface. Never attempt passing on steep upgrades or downgrades.

*When passing a vehicle or changing lanes, signal in advance and double check mirrors for oncoming traffic.

*When completing a pass, look in your mirror, if you can see both of the vehicles front tires on the road surface behind the trailer it is safe to signal and pull back in that lane.

*When passing, or being passed, anticipate the need to make steering corrections due to the air pressure created by other vehicles.

*Always be cautious of the road shoulder when passing. If the trailer gets on the shoulder it can jackknife or cause you to lose control.

Upgrades and Downgrades
Some vehicles have transmission tow modes. Consult your owner’s manual for the proper gears to use on your tow vehicle when towing a trailer.

*Downshift on downgrades to lessen the braking action required. Reduce your speed. Remember that trailer sway is more likely to occur when descending inclines.

*Downshift on upgrades for increased acceleration and power.

*On steep or long downgrades, reduce gears and avoid prolonged brake use on the tow vehicle. The brakes can easily overheat. Use the vehicle brakes in intervals.

*If the trailer becomes unstable when descending an incline and the trailer starts to sway, reduce your speed, avoid using the vehicle brakes, and manually activate the trailer brakes to regain control.

*On steep or long upgrades monitor all of the gauges on the tow vehicle instrument panel. If gauges do not read in the normal range, or the vehicle starts to overheat, pull over as soon as you safely can and call for help.

Safe Driving Tips
Some of these tips apply to pulling a trailer, some apply to driving a motorhome and some apply to both.

*Don’t speed. Driving at a moderate speed will put less stress and strain on the drive train components of your tow vehicle. It will also reduce the likelihood of the trailer becoming unstable and starting to sway.

*Monitor the gauges on the tow vehicle or motorhome instrument panel. If a gauge does not read in the normal range pull over as soon as it is safe, and call for help.

*Drive defensively! Stay alert and monitor what is going on around you at all times. Use your mirrors. For increased visibility, purchase some convex mirrors that you can apply on your side view mirrors. These mirrors are inexpensive and are available in auto parts stores. They come in different sizes and will improve your visibility a great deal, especially along the sides of the RV and in blind spots.

*If you’re pulling a trailer it may be necessary to add mirror extensions so you can see along the sides of the trailer. The mirrors on your tow vehicle can be your best friend when you’re towing a trailer. When you use your mirrors you will know when a transfer truck is passing, and you can anticipate the need for a slight steering correction when the trucks air pressure causes the trailer to move.

*Use the proper gear for driving conditions. If the transmission continues to shift in and out of overdrive you need to turn the overdrive off. Reducing gears can help to slow the trailer or motorhome down when descending inclines and give you the additional power you may need when ascending inclines.

Note: Read the tow vehicle owner’s manual for proper gear selection when towing.

*Try to avoid sudden stops. Stopping to quickly can cause a trailer to slide and possibly jackknife.

*Try to avoid quick, harsh steering movements if possible. This can cause a trailer to become unstable and increase the possibility of trailer sway.

*Slow down on loose road surfaces, such as gravel, and when the roads are slippery and wet.

*When towing a trailer or a vehicle behind a motorhome you need to make wider turns than you are accustomed to. Remember the pivot point for the trailer is its axles. Watch for tail swing and exercise caution when turning on narrow streets and maneuvering around fuel stations.

*When maneuvering around the campground, watch for tail swing, low branches and utility hook ups.

Happy Camping,

Mark Polk
RV Education 101
RV University

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  44. Patrick W. Tribbey

    I’ve investigated the Hensley Hitch, and have finally found someone endorsing it! Presently, I’m towing a 29′ Timberland witha ’93 Chev., 5.7L, auto trans, longbed and have had a few problems with sway. The sales rep from Hensley gave me some local owners to call–which I haven’t done———–yet. Their price is rather EXPENSIVE–even for a used hitch. Does the Hensley eliminate the add-on sway bar? How about the ‘pushing-out pulling-in’ effect from the 18 wheelers and other vehicles? Any info/comments appreciated!
    I do very much appreciate this type of article. Looking for 3/4 T. p/u presently just for the extra power… Chev has 203,000+ and doesn’t shift into O/D as often as it used to. 🙁 [Like me—rode hard and put away wet to many times].
    Thanks, again! 🙂

  45. Serge Cossette

    trailering life is divided into two parts: before towing with the Hensley-Arrow and after.

  46. Dena,

    Unless the hitch you are using already has some type of built in sway control, like an Equalizer Hitch, I strongly recommend you add some type of sway control to the trailer. The weight of the trailer is not going to keep it from swaying!

  47. Dena Babineau

    Hi, I have a question to bounce off anyone that can shed some light on a sway bar question. I originally had a 24 foot travel trailer of which i traded in for a 34 footer. The dealer said i no longer need the sway bar attachment and didnt install it, commenting that the trailer is large/heavy(8500lbs) and wont sway much. Is this true? Not sure if im paranoid or not but his comment surprised me and dont really feel safe without the sway bar attached. The trailer is parked at a campgound seasonal and goes on road trips 2 – 3 times during summer months.

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  49. John Shelton

    There are SOOOOO many good write-ups (this one included) concerning preventing sway and very few describing in detail how to handle sway after it is occuring.

    The biggest mistake that drivers make when the trailer tries to make a direction change of its own is to over correct. If your tow vehicle isn’t headed to another lane or in some undesirable direction, just lightly apply trailer brakes, lift your foot from the accelerator, and hold the steering wheels pointed the direction you want to go. If the tow vehicle isn’t trying to actually “go somewhere” undesirable, you really don’t have a significant problem at this point. The problem comes when you correct for a perceived problem that really didn’t exist to begin with. I have had trucks pass me and surprise me with a huge gust of wind that leans the trailer to one side and tugs at the back bumper of the tow vehicle. Unless the tow vehicle actually moves toward an undesirable direction, steering correction is not necessary. If it does move toward an undesirable direction, make only the required correction necessary to return to desired path and no more. Do this smoothly and calmly, do not make a panic reaction. This is just saying the same thing that recognized experts advise, I’m just saying it in different words.


    The best way to prevent trailer sway is to get a Hensley Arrow hitch.

  51. Harold DeVries

    AMEN Brother been through it.

  52. Dave Williams

    Sway is always of significant concern when towing with a standard equalizer hitch. There are, however, alternative hitches that prevent sway. Having towed for years with traditional weight distributing hitches, I converted to the Hensley Arrow hitch a year ago for towing my 32 foot travel trailer, and was astonished by its effectiveness in eliminating sway.
    Now, I consider this hitch to be the first necessity in towing. All other factors mentioned in this article merit consideration and awareness, but the need to employ them are minimized or eliminated by the geometry of the hitch.
    Last spring, we towed back from Key West in 40 mph winds. The only noticeable impacts of this wind were a reduced gas economy and some speed loss when we headed directly into the wind.

  53. gmas

    Good info that really should be made into a intro to RV towing video…that all should watch before getting out on the road.

    After many years of towing trailers and pushing motorhomes, using the trailer brake override is one of the more important lessons that a newbie could learn. ( I once instructed my X to move the little handle on the controller so she could see what effect it had on the AS… she reached down and shoved the handle over fully… the 31 ft AS tires stopped rolling… and after I picked myself up from under the PU dash… looked at her… to which she responded.. well I guess we know what that thing does … so let that be a warning to you) That being said however, they should be cautioned about over use of the trailer brakes so as not to have them fade out when they need them the most. As most are still drum type brakes they won’t be getting the cooling that you can expect from a newer vehicle today.

    The other factor that was not mentioned was the proper tow vehicle. Here the weight of the tow vehicle is a must to consider with respect to the size of the trailer. What most newbies look at though… is the overall ability to pull… instead of stopping. The tow vehicle should be able to stop the rig within a reasonable distance…using only it without the addition of the trailer brakes. If it can’t you need a better bigger tow vehicle. I know we had a heated conversation about the toyota vs the US made PU tow vehicles. What most didn’t figure out was that the smaller trucks just don’t have the ability to stop a heavy normal rig today. We see the results of this on the road as the rig jacknifes and either rolls or does major damage. Some lose their lives. It is quite a topic of heated conversation when one discusses the smaller import trucks vs the domestic larger ones. Most point to the savings in mileage of gas or diesel as the selling point for the smaller imports. However, they are missing the major factors besides the gas mileage ….. one of which is the braking or stopping effort that the vehicle can provide. (ya we saw the commercials.. but consider that sales hype .. and you don’t see them anymore now do you.. after they could not repeat the proof test)

    3/4 t Ford.. of which we use… now offers a sway control built right into the truck to help keep the user from having problems. Most don’t know it even on as they toddle down the road.. but without it on …you know something is missing very quickly.

    While true that WB could pull a AS with a bike… getting it stopped is a whole nother factor. (makes me wonder if the guy on the bike got run over by the trailer after he applied the brakes on the bike)

    Going to a dealer and hearing him sell the import is a lot like the TV sunday preacher… who says believe in me… I know… what you need… (yet he never has pulled more than a U haul) He is not the one going to pull the rig nor is he going to stop it. You as the owner/buyer should beware.

    This would make a good post article placed in the towing information section… what to look for in a tow vehicle.. and what to check in the specs before you buy one. With the vast pool of people who have towed for years here on the web… it should be a excellent draw for a article or video ref file.

    While insurance can replace the rig… it can’t repair the terror/damage done mentally when the beast gets out of control.. Education and training in this area is really lacking and should be addressed by the industry and users before it has to become a test at the DMV before you can pull your rig.

  54. GlenO

    Great article. I pull a 5er and naturally don’t get the sway effects to the extreme of a tow behind but just recently got caught in some extreme gusty side winds in the IL/MO area. I definatley could feel the sway effect with even a 5er, let alone getting a drastic drop in MPG.

  55. this article should be page one of operating instructions for all towable’s.thanks

  56. Dalton Tamney

    Everything you recommended is absolutely true. I have towed trailers for over 20 years and have experienced some pretty hairraising events. I have been very careful to follow the suggestions as to hitch weight, tire pressure, sway bars, etc. The only equipment which completely solved the problem was the Hensley hitch. I have used it for 4 years now and have experienced sudden strong sidewinds in the mountains, sustained crosswinds on the prairies and numerous semis passing me. Without a doubt it solved the sway problem. It is expensive yes, but it has given me more peace of mind when towing than I have had in the previous 16 + years. Worth every penny. Not for everyone but sure worked for me.