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Old 01-19-2020, 10:53 AM   #321
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Please allow me to offer the following graph as a way to illustrate some of the factors involved in vehicle stability. It's quite simple and even an accomplished engineer should be able to follow it. It shows how vehicle weight and trailer weight are related and how tongue weight affects stability. Note that there is a trade-off between sway at low tongue weights and tow vehicle stability (oversteer and jackknifing) at high tongue weight. The numbers given are of course typical and not fixed in stone, but if you manage to get your rig within the stability triangle you are going to be able to safely tow on the ball without a sway control device.
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Old 01-19-2020, 11:37 AM   #322
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Please allow me to offer the following graph as a way to illustrate some of the factors involved in vehicle stability. It's quite simple and even an accomplished engineer should be able to follow it. It shows how vehicle weight and trailer weight are related and how tongue weight affects stability. Note that there is a trade-off between sway at low tongue weights and tow vehicle stability (oversteer and jackknifing) at high tongue weight. The numbers given are of course typical and not fixed in stone, but if you manage to get your rig within the stability triangle you are going to be able to safely tow on the ball without a sway control device.
In a no-wind condition.
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Old 01-19-2020, 11:58 AM   #323
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In a no-wind condition.
And, on an actual road, not a chart. 🥺

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Old 01-19-2020, 02:46 PM   #324
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Weight distribution and anti sway equipment?

You’ve offered that chart at least a dozen times. Keep trying.

For future readers of the forum - take OOS’s posts with a salt lick....his is simply not good advice to follow....
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Old 01-19-2020, 05:16 PM   #325
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Hi

Rather than make up a chart out of thin air one *could* go try their trailer with and without the AS hooked up. With many systems that's pretty easy to do. Oddly enough I've done exactly that. It is far more stable with the AS hooked up. It is bad enough at 60 MHP in moderate winds that I would not want to tow very long that way. The truck sway protection cutting in every few minutes makes things exhausting.

With the AS hooked up, you can go 70 MPH in 40+ MPH winds and it's stable going down the road.

I've been told that If I had a two vehicle that weighted 20,000 pounds things might be different .... don't have one of those ....

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Old 01-19-2020, 06:38 PM   #326
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You’ve offered that chart at least a dozen times. Keep trying.

For future readers of the forum - take OOS’s posts with a salt lick....his is simply not good advice to follow....
That chart on paper is far more accurate advice then what is offered by most here on this forum.
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Old 01-19-2020, 07:01 PM   #327
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That chart on paper is far more accurate advice then what is offered by most here on this forum.


We disagree. You and OOS appear to be either the same person or joined at the hip. Either way - your shared advice doesn’t jive with decades of experience and common sense. As always - do whatever knocks you out. Just don’t expect when you peddle unsafe BS you won’t be called out for it.
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Old 01-19-2020, 07:09 PM   #328
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The claim it's all a matter of TV size is oft repeated, but I haven't seen specific trucks discussed.

So, for the sake of discussion... assume it's true that a big enough TV negates the need for WD and AS; how big a truck would it take to tow a midsize unit weighing, say 7500 lbs, or 30 fter coming in at 9000 with just the hitch on ball?
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Old 01-19-2020, 07:44 PM   #329
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The claim it's all a matter of TV size is oft repeated, but I haven't seen specific trucks discussed.

So, for the sake of discussion... assume it's true that a big enough TV negates the need for WD and AS; how big a truck would it take to tow a midsize unit weighing, say 7500 lbs, or 30 fter coming in at 9000 with just the hitch on ball?
Yes, a HD truck will feel more planted but I think it's less about weight distribution and more about sway. If you don't correct trailer sway within the first few oscillations by applying the trailer brake and backing off the gas, you'll be reaching for a clean pair of boxers. It happened to us once during our first trip and I never want to go through that again.

I won't tow our 27' Airstream on the ball. Blue Ox Sway Pro with 1500# bars works for us. Lessons learned.

Someone put together a video compilation of trailer sway accidents, utility and travel trailers. Watch it and see what you think is a common cause.
https://youtu.be/Z7Kfl97b57s
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Old 01-19-2020, 09:00 PM   #330
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Correction...apply trailer brakes and accelerate.👍

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Old 01-19-2020, 09:32 PM   #331
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Weight distribution and anti sway equipment?

Yup. Absolutely the only way to straighten out an impending out of control sway event if it has started to occur already is hitting the gas hard and the trailer brake manual lever hard as well.

The easier bit is to not get in that situation. If you are not paying attention, the whole rig will end up in a ball in very short order. That’s why some form of reliable sway control is essential no matter what you are driving.
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Old 01-19-2020, 09:48 PM   #332
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I’d like to third that. If you’re in a sway event, imagine the rig is a string. You want to tighten the string end to end. Manually hitting trailer brakes and accelerating the tow vehicle pulls the string tight - run it in your brain a few times - it will make sense.
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Old 01-20-2020, 03:11 AM   #333
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Talk about bad advice given. No do not accelerate, the reason is that sway is speed dependent. A sudden increase in speed can put more energy into the system. No professional engineer or vehicle manufacturer will recommend acceleration in that situation.
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Old 01-20-2020, 03:23 AM   #334
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We disagree. You and OOS appear to be either the same person or joined at the hip. Either way - your shared advice doesn’t jive with decades of experience and common sense. As always - do whatever knocks you out. Just don’t expect when you peddle unsafe BS you won’t be called out for it.
The chart shows the stability relationship between tongue weight and TV to trailer mass ratio at the bottom and tongue weight and TV stability at the top. It notes the variations between specific equipment so the area of stability may shift to the left, right, top, or bottom. The chart is not wrong and is quite informative. The lack of agreement just further proves the lack of knowledge on the topic by those that are giving out advice.
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Old 01-20-2020, 04:16 AM   #335
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Talk about bad advice given. No do not accelerate, the reason is that sway is speed dependent. A sudden increase in speed can put more energy into the system. No professional engineer or vehicle manufacturer will recommend acceleration in that situation.


Go back and reread what 3 of us wrote.
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Old 01-20-2020, 04:39 AM   #336
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The reason I posted the chart and the image of the jackknifed rig was to draw attention to the upper part of the chart. The lower part shows the sway problem and the upper part shows the opposite problem of oversteer. Both of these can do you in.

The hitch industry does not want to talk about oversteer because the oversteer problem is exasperated by the use of their weight distribution hitches. They try to keep people in the dark about it and unfortunately that seems to be working.

The problem is well recognized in the engineering world. This is why the SAE towing standard requires the passing of both a sway test and an understeer test. The understeer test calls for driving around a circle at a speed that develops a certain g-force. If the rig begins to oversteer you fail the test. The intent is to ensure that the tow vehicle won't be pushed around by the trailer resulting in a dangerous jackknifing.

Truck manafacturers want to brag about their towing capacity but that is limited by the capacity of their rear axle. To get around that they use a weight distribution hitch. The problem is that when they take load off the rear wheels by cranking up the spring bars then they fail the understeer test. They are between a rock and a hard place, as indicated by the towing stability chart.

None of this really matters if you can select your rig so that it winds up within the chart's stability triangle. Then you can tow on the ball and you won't sway or jackknife.
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Old 01-20-2020, 05:32 AM   #337
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The reason I posted the chart and the image of the jackknifed rig was to draw attention to the upper part of the chart. The lower part shows the sway problem and the upper part shows the opposite problem of oversteer. Both of these can do you in.

...
You are misinterpreting the chart. If you load a TV behind the rear axle it will lead to understeer - the tendency of the truck to steer less than commanded by the driver. (Top part of the chart.)

This is the result of not using a WD hitch to restore some of the weight to the front steering axle from the rear drive axle.

You seem to think that the biggest danger of WD equipment is loss of traction of the rear axle causing the rig to spin out, which is false.
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Old 01-20-2020, 05:35 AM   #338
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...snip...
None of this really matters if you can select your rig so that it winds up within the chart's stability triangle. Then you can tow on the ball and you won't sway or jackknife.


Then you can tow on the ball and you won't sway or jackknife so long as you face no weather, no emergency maneuvers, no trucks passing your rig, no potholes in the road, no hazards of any kind, no distracted drivers flowing in to your lane while focused on their cell phones, no personal diver error, no acts of God, etc.

There - I fixed it for you.
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Old 01-20-2020, 05:54 AM   #339
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Go back and reread what 3 of us wrote.
SteveSueMac, your explanation about the string is a perfect way to describe it. That said, when you apply the trailer brakes and let off the gas, it will tighten the string.

I accept that accelerating will "pull the string tight" from both ends but it adds complexity and energy to an already chaotic situation. For newbies, first apply the trailer brakes.

*MAKE SURE YOU TEST YOUR TRAILER BRAKES BEFORE TOWING!* You're SOL if you sway and your trailer brakes don't work.

I think it comes down to ones skill level in the situation. KISS method for most will work, accelerate if you if KISS doesn't work. Not everyone has the skill of Neil Armstrong under pressure. What an amazing guy!
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Old 01-20-2020, 07:30 AM   #340
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Thanks Jeff - we can agree - as Desi said in Long Long Trailer — TRAILER BRAKES FIRST!!!

I’d buy KISS first. And to that end - proper loading, combined with weight distribution and sway setup, tire inflation/health, and most importantly, smart defensive driving for the conditions are one’s primary strategies to avoid the emergency scenario in the first place. If that fails and you sway - TRAILER BRAKES FIRST with your hand - not tow vehicle brakes - gas too if you can remember it and fight the urge to use your foot for the truck brakes until you’re straight...
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