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Old 09-11-2012, 09:13 AM   #15
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Originally Posted by MrUKToad View Post

Certainly people towing should address all of the technical sway reduction measures but keeping driving speed down is, in my view, one of the biggest sway prevention methods that there is.
I definately agree with that statement, and I'll stick my neck out and say any travel trailer will sway, if it's towed fast enough.

Additionally, I'll state that not all travel trailers tow the same, and what's more, not all Airstreams tow the same.

As an example, we had a 23' Airstream that we towed a lot, and NEVER had a swaying event. But, later had a 25' that was a bear to tow, wanted to sway all the time, and only stopped after I switched to a ProPride hitch. Interesting also this same trailer wore tires very rapidly, so I suspect that axle alignment contributed to the tendency to sway.

These statements are from my expereince towing trailers, not from an engineering viewpoint as I am not a mechanical engineer.
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Old 09-11-2012, 09:38 AM   #16
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For the record, my 7,300lb 28' International is towed by a Toyota Sienna minivan. Outright weight, power and torque may not be "big numbers" but the stability of the minivan contributes massively to sway reduction and, even with a pair of old-tech friction anti-sway bars, I don't have an issue with sway at all.
That's an interesting TV to be sure. Now, what are the characteristics that make the Sienna well suited? Is there short overhang? Low CG? Stiff tires?

Have you ever towed without any anti-sway bars attached? What do you think would happen?

So, there are kind of two schools: First school is solve all sway issues with a hitch. Second school is solve them with the vehicle and maybe only a little bit with the hitch.

Thanks also for mentioning speed. In my case in California the max is 55MPH with trailer, so I generally hold it to 55-60 no matter where I am. I hear of people going 65-70 though.
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Old 09-12-2012, 10:27 AM   #17
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That's an interesting TV to be sure. Now, what are the characteristics that make the Sienna well suited? Is there short overhang? Low CG? Stiff tires?

Have you ever towed without any anti-sway bars attached? What do you think would happen?

So, there are kind of two schools: First school is solve all sway issues with a hitch. Second school is solve them with the vehicle and maybe only a little bit with the hitch.

Thanks also for mentioning speed. In my case in California the max is 55MPH with trailer, so I generally hold it to 55-60 no matter where I am. I hear of people going 65-70 though.
The Sienna is wide and relatively low and has quite a good overhang to wheelbase ratio, all of which help. It also has semi-independent coil spring rear suspension, which isn't as good as full independent but much better than a live axle with leaf springs - for stability that is. I have stock tires on there which are not bad, but could improve things by using low profile tires; something I may consider when it comes time to replace. The secret really is the hitch receiver, an OEM "Hidden Hitch" model but strengthened with the addition of two pieces of steel welded behind the receiver box and that extend to a point close to the rear axles where they are bolted to the body. This not only adds strength but helps transfer the weight on the hitch forward when the weight distribution system is fitted. I think the Sienna has good payload figures, too, as I don't exceed the axle ratings or the Gross Vehicle Weight.

I haven't driven without the sway bars and neither would I. The trailer is 28 feet long and will be prone to swaying, even with the most stable tow vehicle available. To give you an example, and to show it's not necessarily the TV that will or won't prevent sway, I was caught in an interesting situation last year on the I59, northbound, between Birmingham and Chattanooga. In a 15 mile stretch of construction work, the pavement had been temporarily widened by a foot or two on the right to allow all traffic onto one side of the road. The trouble was that the extended piece was a couple of inches lower than the rest of the pavement and there was a step there which, naturally, the Airstream's wheels found. They kept dropping down the step then back up it (at 50mph) and that making driving quite difficult. What didn't happen, though, was the trailer giving into the sway. The two sway bars stiffened the thing sufficiently to prevent more than just a minor wiggle as the wheels went up and down the step. Being a sensible fellow, I noticed that the Semi drivers all went to the left lane, close to the concrete barrier but not hopping up and down the step, so that's what I did. I was glad when the 15 mile stretch was over, though.

I do think a stable tow vehicle will go some way to helping with sway, but so will a good hitch set up. We only use a basic Eaz-Lift set up but a Hensley or ProPride would, I'm sure, improve things further - another thought for the future.

Speed is quite an issue, particularly in the US where not only are the limits higher than in Canada (mostly) but driving in excess of those limits seems to be almost a right. People on this forum will regularly tell you that they tow at 75mph, because that's what the semis do, but for me, that's way too fast to pull a trailer. Still, that's up to them; I shall continue at 60-65mph safe in the knowledge that I have a stable TV and trailer set up.
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Old 09-12-2012, 11:36 AM   #18
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Quote:
Originally Posted by MrUKToad View Post

For the record, my 7,300lb 28' International is towed by a Toyota Sienna minivan. Outright weight, power and torque may not be "big numbers" but the stability of the minivan contributes massively to sway reduction and, even with a pair of old-tech friction anti-sway bars, I don't have an issue with sway at all.
What year model of Toyota Sienna do you have?

Just wondering because I checked and a 2010 has a manufacturer's maximum towing rating of 3500 pounds, which is not quite half of the weight you are actually towing, so surely you have a different model?
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Old 09-12-2012, 12:17 PM   #19
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Originally Posted by MrUKToad View Post

Speed is quite an issue, particularly in the US where not only are the limits higher than in Canada (mostly) but driving in excess of those limits seems to be almost a right. People on this forum will regularly tell you that they tow at 75mph, because that's what the semis do, but for me, that's way too fast to pull a trailer. Still, that's up to them; I shall continue at 60-65mph safe in the knowledge that I have a stable TV and trailer set up.
I agree, and I go even slower. I tow at about 58 - 62 MPH average speed. I have had my rig up to 75 MPH just to see what it feels like. It was every bit as stable feeling at 75 as 55, but I had no interest to tow at that speed.

Thanks for your Sienna details!
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Old 09-12-2012, 03:56 PM   #20
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What year model of Toyota Sienna do you have?

Just wondering because I checked and a 2010 has a manufacturer's maximum towing rating of 3500 pounds, which is not quite half of the weight you are actually towing, so surely you have a different model?
I have the 2011 v6, 3 litre which yes, has a manufacturer's tow rating of 3,500lbs.

I can hear you catching your breath from here!

Contrary to the opinions of many, the manufacturer's tow rating is neither a scientifically derived figure, nor one that is in any way binding. It's more the province of the marketing departments who appear to pluck such figures out of the air in an effort to get you to buy a vehicle. That's not to say there's no testing done but the figures have been set first, then the testing begins. Here's an article from Truck Trend magazine that bears out what I'm saying:

The Numbers Game: Current Practice & The Ratings - Consumer Feature - Truck Trend

In the case of a minivan, if you do your research you'll see that all makes and models of minivans on the market today have a tow rating of 3,500lb and have done for the past 30 years, despite some very definite advances in design and technology over that period. In reality, manufacturers don't want you to tow with a minivan because that's a "mom" car and they want dad to go out and buy a pick up truck as well. It's also interesting to note that the profit margin on a pick up truck is much greater than on a minivan - need I say more?

So, understanding the dynamics of towing and the need for a stable tow vehicle, my towing guru at Can-Am RV tells me that the Sienna, along with other similarly specified minivans, make excellent TVs. He modifies or fabricates the hitch receiver, improves the transmission oil cooling and adds a brake controller along with a good quality WD system and sway control (back to the original point of the thread!) and rolls out what proves to be a very good tow vehicle, despite the manufacturers arbitrarily set tow rating. They do test these combinations extensively at Can-Am but the real proof is the thousands of satisfied customers who have been using cars, minivans and SUVs as Airstream TVs safely and effectively for years.

I rambled on a bit there but essentially the Sienna, suitably set up, works well for me and plenty of other Can-Am customers.
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Old 09-12-2012, 04:04 PM   #21
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What does Can-Am do to the vehicle to increase rear axle weight rating, cooling system capacity, transmission cooling capacity, and GVWR, etc.?
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Old 09-12-2012, 08:27 PM   #22
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What does Can-Am do to the vehicle to increase rear axle weight rating, cooling system capacity, transmission cooling capacity, and GVWR, etc.?
I can only speak about work done on my TV, which was limited to an additional transmission oil cooler. I don't exceed the axle weight ratings nor the GVWR so no enhancements were needed.
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Old 09-12-2012, 08:41 PM   #23
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I rambled on a bit there but essentially the Sienna, suitably set up, works well for me and plenty of other Can-Am customers.
The Can-Am name seems to come a lot when interesting tow rigs are discussed. Too bad they are so far from me. Although I enjoy my Suburban, I'd be intrigued to know if our V6 Ford Escape could be setup to tow the same TT? I suspect at a minimum my gas mileage would climb by 4 or 5 MPG. Man, that would be nice!

General call out - - does anyone know of people in the USA who do what Can-Am do?
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Old 09-12-2012, 10:59 PM   #24
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I've been towing my rig over all kinds of Interstates, highways, byways and roads for almost a year. Rain, wind, sun. I've towed up and down long grades, flat runs, and through wind-swept prairies. I have had triple trailer rigs go roaring by. And through all this, I can't say that I have ever had any sway of any appreciable amount (such as where I would have to adjust the steering wheel). I have a simple WD hitch with friction sway control.

I am interested to look at what contributes to sway?

- Tires on the TV and Trailer (side wall roll or flex)
- Overhang on the TV - distance from rear axle to ball compared to wheel base
- Improper weight distribution on the TV
- Improper balance of the trailer

Of course we have various hitches to eliminate sway, but my question here is what can be done to stop sway from happening in the first place?

If sway is reduced at the source, how much sway control needs to be in the hitch?

Do different TV types perform better than others in sway? Van vs. PU? SUV vs. sedan?

Can you just change tires and reduce sway?
Follow a boat being towed.

The back end oscillates, to some degree.

The same basic thing happens to an RV, especially the Airstream shell shape
design.

The longer the trailer, the more it oscillates, to some degree.

That oscillation will be experienced if a person rides in the back of the trailer at about 60 MPH.

Once they feel that small sway (oscillation) they then will do something directed towards correction, instead of insisting that theirs doesn't sway.

Not what owners want to hear, but something they should all experience as a fact.

Andy
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Old 09-12-2012, 11:25 PM   #25
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That oscillation will be experienced if a person rides in the back of the trailer at about 60 MPH.

Once they feel that small sway (oscillation) they then will do something directed towards correction, instead of insisting that theirs doesn't sway.
A damped oscillation in response to transient road effects is completely normal, and is NOT a cause for concern. The thing we're concerned about is uncontrolled growing oscillations. Most times, the driver is an important part of causing those oscillations, and if he would stop trying to "correct" things would die down again. However, the stability equations for trailers DO indication some conditions when uncontrollable sway can occur, and the following factors most exacerbate this:

1) insufficient tongue weight
2) grossly excessive speed
3) trailers loaded with high polar moment of inertia.

There are others, as others have commented.

- Bart
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Old 09-12-2012, 11:47 PM   #26
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Hi, almost everything tends to oscillate on our grooved freeways. Seems that most of the problems occur while driving down hill, going too fast, passing or being passed by a big rig, and with some side winds. [driver error]
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Old 09-13-2012, 01:06 AM   #27
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Sway vs. Fishtailing?

Hmmm? I am starting to wonder if there are two separate, but similar phenomena here.

First, if I imagine the ball tracing a straight line, but the TT rear end moving side to side, I would call that a harmless "fishtail." In the second case the ball is moving side to side AND the TT rear end is moving side to side in opposition, I would call that the dangerous "sway", which we are trying to eliminate.

This came to mind after reading Andy's post. His position was that sway exists all the time, whether driver knows it or not. His evidence was the tail end of the TT swinging side to side when view from behind (paraphrasing).

When I said in the O/P that I don't feel sway, I mean that I don't feel my TV moving. The TT might in fact have some side to side (Andy's motion), but my TV seems stiff enough to resist. I am not making any steering corrections when big semis blow by. (I use a friction style anti-sway).

It would be hard for a fishtail of the trailer alone (ball not moving) to amplify out of control, whereas it is easy for the "sway" (ball moving side to side) to amplify out of control. Driver over-correction would of course be common.

It would be easy to imagine some reasons that the TT might be fishtailing all the time. Road surface, axle or tire alignment, tire balance, to name a few. It is also easy to imagine that TVs have a wide range of resistance to side force at the ball. I've never seen any metrics on this. Like, how much side force would it take to move the ball 2" east to west? Just a thought.
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Old 09-13-2012, 06:46 PM   #28
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I can only speak about work done on my TV, which was limited to an additional transmission oil cooler. I don't exceed the axle weight ratings nor the GVWR so no enhancements were needed.
Have you actually weighed it loaded with the trailer hooked up and ready for travel to be sure? Or, are you just trusting Can Am to know more about your Toyota than Toyota does?

Seems odd to me that a 1/2 ton pickup truck normally does not have enough RAWR to carry a trailer as large as yours, but a minivan does?
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