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Old 03-20-2010, 09:44 PM   #1
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Rivet The Demon behind the car carriers and sway control

We just returned from a 2,000 mile shake down trip to Florida and while coming back had a car carrier carrying a mix of brands get in front of me and as soon as another truck came alongside I felt the trailer sway back and forth. I looked out the rear view mirrow and could see out the back window of the twinkie and it was going side to side 6 to 8 inches rythmicly so I let off the gas and dropped back 20 feet and a few mph from 65 and it stopped immediately. I then resumed the 65 mph and everything was fine. On the trip we had square box tractor trailers pass and pull in front while another pulled alongside at 65 and had no problem whatsoever. Thank goodness I bought the Reese dual cam unit or I think it would have been much more interesting. The TV was rock solid just the Argosy dual axle doing a wag the tail like a puppy.

For all those who figure oh why bother with sway control pulling your seat out of your dairy air is a hoot.
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Old 03-20-2010, 09:48 PM   #2
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OK I'm getting sway controls.
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Old 03-20-2010, 09:49 PM   #3
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I have not encountered a sway condition yet, but I try to keep the rules in mind while towing. I thought one of the rules to stop a sway was to speed up, but you had good luck with slowing down. Either way, I'm glad you had a good hitch and were able to get everything back under control! I dread the day we'll experience it!
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Old 03-20-2010, 10:25 PM   #4
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The fastest way to stop a sway is to speed up and apply the trailer brakes at the same time. If speeding up is not available, then just applying the trailer brakes will do. JMHO
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Old 03-20-2010, 10:30 PM   #5
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John,

Im glad everything worked out as it did. Sway is scary. Reducing the speed was the right decision. Im using the reese dual cam and having no issues even when big trucks pass. Who knows how those carriers break up the airflow but obviously you were affected. I will keep that in mind when I see them come by now..

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Old 03-20-2010, 11:09 PM   #6
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I have the Reese W/D dual Cams with 800lb sway bars and just drove for the first time this week ove r800 miles and do feel a little "push" when Semi's or speeders zoom by me. Nothing bad, just a little push. I know when someone is in my blind spot. I assume thats normal. I couldn't imagine not having sway control.

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Old 03-20-2010, 11:32 PM   #7
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Wow - that seems a bit off...

I used to tow two Harley Davidson Ultra Classics and Sportster in a 22 foot Haulmark low profile trailer (4,800 lbs) just sitting on my Cayenne's tow hitch (Granted - air bag suspension but no sway hitch or load leveling) and would go from my home in the DC area to Daytona and Myrtle Beach all the time on Highway 95 cruising at 80 with big semi's and all - never had the rear end wiggle....

You did with even "low-end" equalizer\sway hitch setup - something seems off - perhaps how you are packing your trailer - vehicle, tire pressure, etc....

Feeling the "bow wave" is one thing - but that shouldn't be causing any sway when they go by - and remember - if you do get some sway maintain your current speed (don't decelerate) while manually giving your trailer some brakes via your brake controller - last thing you really want to do is change your tow vehicles speed and make things worse...
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Old 03-20-2010, 11:52 PM   #8
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I agree.. and should clarify, reduce your speed with the trailer brakes. I have hit the manual override many times and let the trailer do the work. It will straighten you out immediately. You were already doing 65mph so I dont think there was a need to speed up anymore just hit the controller and things should settle down.

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Old 03-20-2010, 11:59 PM   #9
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While your trailer was swaying back and forth, what you were likely feeling & seeing was a normal reaction to vortex shedding from the car carrier rather than a self-reinforcing oscillation such as is caused by insufficient tongue weight.

Since tires on a roadway cannot develop side forces w/o a slip angle (the angle between the apparent direction of the tire and the actual track), when the wind pushes the trailer, it moves over. You'll also notice this on a canted road; the trailer moves to the downhill side slightly. This happens regardless of sway control mechanisms.

Large trucks will shed vortexes off of one side and then the other; this causes strong aerodynamic buffeting and will bump your trailer back and forth, both rocking on its suspension and changing the track of the tires. Anyone who's ridden a motorcycle on the freeway in traffic is well aware of this phenomenon.

These pulses from the vortexes will cause any trailer to rock back and forth; this is normal and should not be a cause for alarm. The amount of resulting oscillation will be affected by the various types of "sway control" hitches, but since there's external forces moving the trailer, it _will_ move somewhat.
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Old 03-21-2010, 12:01 AM   #10
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I have felt that same thing from car carriers! Sometimes, tankers too! But, worst from the car carriers. I just back off a bit to let them get some distance from me and it all quiets down! Unique phenomenon.
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Old 03-21-2010, 07:17 AM   #11
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Just to clarify it was a car carrier with a used vehicle mix, truck, car, van, moose, etc. that made it occilate, other car carriers (all cars) or normal box trailers were no problem.

As soon as I let off the gas and dropped 2 mph and a few feet back it stopped before I could reach the trailer brake controller.
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Old 03-21-2010, 10:02 AM   #12
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CarCarriers catch more air and are carrying more air than any vehicle on the road. I haul cars for about 8 yrs. That's the hardest pullin load I have ever experienced. I have also ridden my motorcycle around big trucks and the vortexes can be wicked.
I dont have much of a problem with them,I do use the Reese straightline and my TV is heavy,but I can still feel it,but have not had any problems with sway.
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Old 03-21-2010, 11:09 AM   #13
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Car carriers are do not produce a "clean" air flow around them like a normal semi's sealed box configuration. They also travel much lower to the road surface than a normal truck. The box on most semi's is about 3 feet or higher above the road surface the vortex or wind wave that they produce is much higher and dissipates somewhat in the empty space above the road. The Car carriers have the bottom deck traveling not much higher than the bottom of your vehicle/trailer combination combine that with multiple vortexes coming from the different vehicles on the car carrier and you will get a lot of buffeting. When you see a large low vehicle coming up for a pass try moving slightly to the left in your lane which will cause them to unconciencely move more to their left when they come up on you in the adjoining lane. When their front gets to the back of your trailer move slightly to the right of center in your lane putting a little more distance between them and you. That should mitigate some of the buffeting.
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Old 03-21-2010, 02:44 PM   #14
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I'll be watching out for car carriers when we tow from now on! We have occasionally felt buffeting from large trucks or winds in the gorge (the van feels it as much as the trailer), but no sway. I'd like to keep it that way.
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