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Old 05-16-2011, 01:10 PM   #1
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Question Did I experience sway?

As I was towing the Airstream this weekend I noticed that when a large vehicle (pickup with horse trailer, 5th wheel, motorhome) passed me that there was a "sucking" sensation. When the "sucking" sensation occured I had to correct for lane position slightly as they passed. Was this sway?

TV: 2011 F150 Lariat Supercrew 5.5' Box 145" Wheelbase
Hitch: Equal-i-zer 12K <-- Dealer Chose & Installed - I've verified many ways that the hitch is overkill and setup correctly doesn't pose an issue.

I have changed tow vehicles and re-setup the hitch myself follwing directions provided by Equal-i-zer. I still need to verify all of my weights and hope to this weekend.
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Old 05-16-2011, 01:21 PM   #2
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RellikJM,

I have a 2008 Safari and my TV is a 2010 F150 Super 4x4. Afte3r much thought and reference from here, I went with the Eq 10K. I does well but I think I'm just right or slightly over with the 10K set-up.

The motion you are experiencing is buffeting from the air cushion pushed but the other vehicle. It would be the same as if you were not moving and the same passed you. your vehicle would "Rock" by the air cushion moving past you. So, it technically is not sway in the terms of trailer causing your TV to wag it's tail.

Of course, always be cautious of vehicles passing you as the air cushion can cause your TV and TT to laterally move for an instant.
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Old 05-16-2011, 01:26 PM   #3
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Often something like that leads to sway. If you look in the rearview mirrors after a large vehicle passes and observe that the trailer moves side to side several times before settling down, that would be sway.
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Old 05-16-2011, 01:35 PM   #4
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This is in that grey area of definitions; here I think your dealing with a pull or push from the air, where sway would be a back and forth motion often caused by excessive speed or not enough weight on the front of the trailer. However, if your are only marginally outside of the conditions that cause sway, this push or pull could induce sway.

We had the same thing with the trucks passing when we first bought our trailer. Two things minimized it. We called Andrew Thomson at Can Am Rv in Canada, an Airstream dealer and towing expert, and he recommended getting rid of the P rated tires on our Tundra pickup and replace them with a extra load tire. Our movement from the push and pull of trucks was mostly in the pickup tires. That was the most dramatic improvement. On his advice, we also adjusted the hitch head of our Equalizer slightly downward, so the bars would tighten when the trailer moved to the side. That helped as well, but especially with the Equalizer brand, their is a cautionary note because its stiff bars could possibly bend the trailer A-frame under certain conditions. The dealer also installed too big of an Equalizer on your trailer, even though they and Equalizer company will say its okay. The bars need to flex in order to maintain constant sway control while moving over uneven roadways.

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Old 05-16-2011, 01:49 PM   #5
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I had a like issue and increased the pressure in my tv tires from 30 (as noted on the tv door post) to 35 psi. The buffeting is not totally gone but the increase in pressure greatly reduced the issue. I don't think you can totally eliminate the movement. Large trucks move a lot of air.
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Old 05-16-2011, 02:00 PM   #6
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Not to be a smart aleck - but I towed a 25FB Classic with a short wheelbase "Touareg TDI" and never experienced any sway, regardless of cross winds (had some big ones - especially when in Nebraska-Colorado for some reason), large rigs passing me, etc.
OK - I fibbed, during some 40+ mph gusts at 75mph I had a little sway, in this one instance I slowed down to 65mph and the sway went away - (yes, we can argue I should not have been towing at that speed but it will only fall upon deaf ears......)
I would have to say that my ProPride hitch worked it's crazy magic - projecting the hitch point forward and mitigating any sway occurrences (within reason of course).
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Old 05-16-2011, 05:39 PM   #7
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Here in South Dakota we have so much side-wind (different than under table wind), that when a tall vehicle passes us we have side wind disruption syndrome. It's like we have a 45 mph side-wind, then no side-wind, then 45 mph side-wind again. I've followed semis fighting vacume and wind changes when they're passing. A double trailer rig can really do a dance.

I've towed for decades and have been buffeted but never busted. My neighbor lost a tandem enclosed trailer right over an overpass from cross winds. Took it right off the hitch and chains.

My trailer'd be like driving down the road with a 8' X 30' sail behind me. Here a calm day is a 30 mph wind.
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Old 05-16-2011, 06:16 PM   #8
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Here in South Dakota we have so much side-wind (different than under table wind), that when a tall vehicle passes us we have side wind disruption syndrome. It's like we have a 45 mph side-wind, then no side-wind, then 45 mph side-wind again. I've followed semis fighting vacume and wind changes when they're passing. A double trailer rig can really do a dance.

I've towed for decades and have been buffeted but never busted. My neighbor lost a tandem enclosed trailer right over an overpass from cross winds. Took it right off the hitch and chains.

My trailer'd be like driving down the road with a 8' X 30' sail behind me. Here a calm day is a 30 mph wind.
Wow, that's something to keep in mind if we ever make that trip to Mt Rushmore! We certainly don't experience winds like that out here!

I've never felt sway, but we often feel 'pushed' by those big semi's blowing by. I feel the same 'push' even if it's the van without the trailer.
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Old 05-16-2011, 06:29 PM   #9
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If you have ever stopped on the side of the road and had an 18 wheeler blow by, you can get a good idea of the forces being applied to the trailer.

It is amazing the amount of air being pushed by these rigs, It will make the trailer and the TV shake as they go by.
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Old 05-16-2011, 06:31 PM   #10
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I've never felt sway, but we often feel 'pushed' by those big semi's blowing by. I feel the same 'push' even if it's the van without the trailer.
Something that just came to mind: The 18-wheelers are using a new "skirt" on their trailers to decrease wind drag underneath and, of course, improve mileage. They are VERY dangerous to all of us; we got knocked around big time whenever one came by us. Keep an eye out for the white shrouds, and hold on with both hands!
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Old 05-16-2011, 08:01 PM   #11
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Wow, that's something to keep in mind if we ever make that trip to Mt Rushmore! We certainly don't experience winds like that out here!

I've never felt sway, but we often feel 'pushed' by those big semi's blowing by. I feel the same 'push' even if it's the van without the trailer.
The Black Hills don't get those high winds too often, but east of Rapid City hang on.

The motorcycles lean into the wind so far, so long, that they wear their tire tread off on one side only. The only way to get equal tire wear is to make a return trip going the opposite direction.
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Old 05-16-2011, 08:26 PM   #12
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I have experienced this push -pull effect too. It's interesting that it is worse when a van or other larger truck passes you rather slowly going the same direction on the interstate. Trucks going the opposite direction on a 2 lane road seem to have no effect.

This reaction is minor, subtle, and not dangerous as far as my experience goes. But after a full day if driving I get tired of it. I mostly eliminated it by installing an old school friction antisway bar.

I like the suggestion of upgrading the TV tires from P-rated.

Bill aka cosmos
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Old 05-16-2011, 08:46 PM   #13
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Something that just came to mind: The 18-wheelers are using a new "skirt" on their trailers to decrease wind drag underneath and, of course, improve mileage. They are VERY dangerous to all of us; we got knocked around big time whenever one came by us. Keep an eye out for the white shrouds, and hold on with both hands!
Mike,

I have begun to see those everywhere. I will keep an eye out for them when towing.. usually they blow past me so I will just hang on!
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Old 05-17-2011, 06:38 PM   #14
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I think what you felt was exactly a mild "sway". The passing rig pushed a wall of air against the rear of your trailer. The the trailer moved away, the front of your truck moved left.

The felt effects are different it you have a Hensley or ProPride.

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Old 05-17-2011, 07:16 PM   #15
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What you experienced was probably bow wave effect from air displacement when the truck approached and passed you. Check out this thread http://www.airforums.com/forums/f463...low-58771.html
for some good reading or do a search using key words for more info on the subject.

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Old 05-26-2011, 07:17 PM   #16
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Remember that the drive axle of the TV is the Steer Axle of the TT (in a manner of speaking). The driver has more movement to control with the TV Steer Axle, so any movement from elsewhere has a peculiar and unsettling feeling associated with it.

With body-on-frame vehicles with crude suspension (live axle, etc) the movement of the body against the suspension at the rear is the culprit. The Drive Axle also tends to feature stiffer springs, but this may do little against side-to-side movement. The wind forces -- especially abrupt ones as described above, and by Inland Andy elsewhere -- that reverse direction are more than unsettling, they become threatening.

Mr. Thomson is correct about TV tire sidewall stiffness. IMO, a rear anti-roll bar is also recommended (as are poly bushings for it and the front bar).

Power steering systems also tend to mask the beginning of this phenomenon, so see to it that any "dead center" is better than new. Older shock absorbers are also part of the problem, so an upgrade to BILSTEIN is recommended.

Is any of this "sway". Precursors, yes, but one needs a camera to say when these forces (and the reactions of the vehicle plus the actions of the driver) cause this sway (yaw) to become a problem.

A few suitable upgrades, some mechanical adjustments to the TV, and then hitch rigging as sorted by weight scale readings will take care of almost all of this (assuming a decent hitch system). A sway eliminating hitch system (such as Pro Pride) is a best idea. Beyond that, trailer disc brakes and finest controller.

In other words, do some homework (reading around here), ask questions and verify with numbers.

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Old 05-26-2011, 07:34 PM   #17
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Came along the I90 south of Rochester NY on Monday and experienced a lot of that sucking effect as the big trucks passed. There was a nasty side wind which was making it seem all the worse. However, the Airstream just followed what ever the TV did and showed no sign of sway, just leaving me to adjust my road position as the truck passed. We have friction anti-sway bars that won't prevent sway but will dampen it if it starts.

If you think it's bad when towing, though, you should try it on a motor cycle!
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Old 05-26-2011, 08:22 PM   #18
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There is no such thing as swing.... without sway.

Get camping....
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Old 05-26-2011, 08:35 PM   #19
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What you experienced was probably bow wave effect from air displacement when the truck approached and passed you.

Rich
There are 2 forces at work it seems. First the bow wave that pushes you away from the passing vehicle. This is immediately followed by a reduction in pressure which sucks you towards it. You get a double whammy when the trailer is hit by the same.

Keep a weather eye on your mirrors for large overtaking vehicles, pull to the right as far as possible, ease up the gas and cover the brake. There is a tendency to over correct steering setting up a dangerous reciprocating sway.

IMHO the worst vehicles seem to be car carriers.
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Old 05-26-2011, 11:34 PM   #20
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There are 2 forces at work it seems. First the bow wave that pushes you away from the passing vehicle. This is immediately followed by a reduction in pressure which sucks you towards it. You get a double whammy when the trailer is hit by the same.

Keep a weather eye on your mirrors for large overtaking vehicles, pull to the right as far as possible, ease up the gas and cover the brake. There is a tendency to over correct steering setting up a dangerous reciprocating sway.

IMHO the worst vehicles seem to be car carriers.

I would like to modify parts of the above. Defensiveness is not timidity (that's how it is interpreted while on the road; and, as this is America, to be taken advantage of: "I'm driving faster so they should move over for me"), and the passing vehicle DOES NOT have right of way over the vehicle being passed. In fact ALL obligation is upon them, for practical purposes. (Speeders have no defense, here).

1] It is your lane (speaking here of the Interstate), so stay centered in it. Others have a tendency to move towards a vehicle that is in the right of it's own lane. Dumbo Americano. They nearly none of them know where the right side of their vehicle is, so they tend to ALWAYS maintain the same distance to that side. You move over and they follow. (Don't believe me, then try it out).

I tend to move the rig towards the left lane, and then move back just a bit past center towards the shoulder when the other vehicle is almost on top of me.

I give the other a psychological "push" in other words. This works well whether I'm solo, towing a trailer or driving a tractor-trailer. I maximize the distance at the right moment, but DO NOT give up the center of my lane to do so. These aren't big movements, but adjustments of lane position. They work. I am riding across the big truck rut trough from one wave top to the other wave top is about what it amounts to (for you water skiers). Just enough that the usual morons adjust their position in the passing lane.

We're dancing . . . and I'm taking the lead.

(If I'm worried about someone coming up I may in fact wander all over the lane and literally over into his before they're next to me . . sobers them up quickly I notice: get around that crazy driver!!).

One needs all of the room of his lane that he can have. And only from the center of his lane can he be sure of this space; sacred space in a manner of speaking as travel trailer rigs are so very limited in handling..

Do not let others intrude . . push 'em over (don't have the brainless anywhere near you, for any length of time).

The passing vehicle tends to have chosen a path past the slower vehicle a fair distance back, usually unconciously. I want him over in his lane as far as he'll go, relatively.

The decent ones out there will already be over a little and well above 5-mph more than my speed. Those who are barely passing or who are sorta passing (on cruise control), and those who travel in the cretin packs bumper-to-bumper with others are not the decent sort!


2] I would also NOT ease up on the throttle, but set the speed -- with positive forward momentum at all times -- to one that is lower; a bit. Come off the cruise, perhaps, but have NO slack in the rigging (no deceleration occurring) when any other vehicle is near. In fact, if I am worried over who or what is passing I may in fact be accelerating as they pass me. Not much, and not enough to cancel the speed difference between us, but enough that it is more difficult for the passing bow wave (or waves) to affect momentum.

(For the occasional speed limited big truck barely getting around me, I just drop off the cruise and let him get past then get back over, wait till there's proper distance and glide back up to my travel speed, re-setting the cruise. Never stay near a big truck no matter who is passing. And, big trucks never want to stay in the passing lane!! Do what you can to shorten that time for them).

Again, this is all rather gentle in effect. My passenger may not notice and my conversation may not flag, it's pretty well automatic. I am only re-setting my steady state to one slightly different (but I've also been doing these things for nearly forty years).

When it is not gentle then I will in fact be moving as far over as possible and down to below 50-mph -- and re-accelerating somewhat -- for the truly scary once-a-decade stuff (a trio of tractor trailers at above 100 mph; never forgot that one .. was all the way onto the shoulder for that).


3] The brake to cover is the brake controller, not the TV service brake. If the rig starts to sway then slam the trailer brake home and slam the TV throttle down at the same time. It's not easy to lock the trailer brakes so that the TT tires slide, but anything to slow the trailer back to the speed the TV is traveling is key. (And this is why one wants positive forward momentum: so that the steering slack is already taken up . . that trailer is going to jerk and jerk hard once the brakes hit.) This is where steering over-correction will occur.

A swaying trailer is trying to pass you. You might reconsider that cutesy name so many are fond of giving theirs as it tries to jerk the TV drive axle loose from it's grip to yank you both into the ditch while at a highway speed.

Do what you can to avoid getting to that point. As was drilled into me, "There's no such thing as an accident". Wherever the margin to improve your rig can be found, incorporate it. A few $$ will mean a lot in worsening situations of road, load, traffic and weather.

And a fair amount of this is moot for those with either crappy hitch rigging or no WDH. It'll be enough work to keep the danged thing straight in the same crosswind that day. Forget the forms of signaling to others as above.

The best hitched rigs can have more than just sway elimination going for them . . same for best brakes, best brake controller, best tires at best pressure, etc, etc, et. al. Those little movements of offense are the best defense, IMO. Get the maximum distance and the minimum times.


As to car carriers ("parking lots") the worst possible fuel mileage for any big truck is that type with a 3/4 bow wind off either side. Empty or loaded they are aero nightmares and in having one pass we experience in miniature the reversing wind phenomenon spoken of above and elsewhere usually associated with several trucks.

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