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Old 01-20-2020, 07:38 AM   #341
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Originally Posted by Profxd View Post
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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Originally Posted by out of sight View Post
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, 08:06 AM   #342
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It may seem counterintuitive, but look at where the trailer inertia is. If the tongue load is too high it means that the center of gravity is too close to the hitch point. This is good for preventing sway but bad for preventing jackknifing. The trailer inertia becomes too great and when you make a turn with the tow vehicle the trailer wants to go straight. That puts a sideways load on the hitch ball, pushing the back of the truck further than it should, resulting in oversteer when the tires begin to flop over on their sidewalls. If the force becomes severe enough the tires break traction and you jackknife. If you remove weight from the rear tires with a wd hitch the sidewalls will roll over much easier. Note that the inertia of the trailer is still there but the traction to resist it is lessened.
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Originally Posted by Adventure.AS View Post
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, 08:14 AM   #343
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Originally Posted by out of sight View Post
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.
No, "exasperated" is what thinking people are after reading your reams of nonsense and FUD. You saw one (marketing) photo of a Toronado without rear wheels and in your fever dreams imagine that everyone it taking all the weight off their rear axle with the evil weight distribution devices that are going to destroy the universe.

While I understand you're immune to data that doesn't confirm your personal biases, when properly adjusted for travel with my Blue Ox hitch, my rear axle carries about 600 lb more weight than when unhitched. How you imagine it would have less than the unhitched weight with any reasonable adjustment of a hitch system is beyond me.
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Old 01-20-2020, 08:20 AM   #344
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Originally Posted by out of sight View Post
It may seem counterintuitive, but look at where the trailer inertia is. If the tongue load is too high it means that the center of gravity is too close to the hitch point. This is good for preventing sway but bad for preventing jackknifing. The trailer inertia becomes too great and when you make a turn with the tow vehicle the trailer wants to go straight. That puts a sideways load on the hitch ball, pushing the back of the truck further than it should, resulting in oversteer when the tires begin to flop over on their sidewalls. If the force becomes severe enough the tires break traction and you jackknife. If you remove weight from the rear tires with a wd hitch the sidewalls will roll over much easier. Note that the inertia of the trailer is still there but the traction to resist it is lessened.
In this scenario 1. you are travelling to fast for conditions, 2. you mustn't have trailer brakes.
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Old 01-21-2020, 03:24 AM   #345
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There is a ideal balance between understeer gradient and sway damping ratio which is unique for every TV/ trailer combination. The chart shows an example of this and is indeed based on real physics. I don’t understand why you guys think that facts can be completely disregarded in favor of your opinions. Hopefully these arguments drive the new to towing folk to learn the facts for themselves and ignore quick answers on RV forums.
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Old 01-21-2020, 06:47 AM   #346
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No sway here....

Quote:
Originally Posted by Profxd View Post
There is a ideal balance between understeer gradient and sway damping ratio which is unique for every TV/ trailer combination. The chart shows an example of this and is indeed based on real physics. I don’t understand why you guys think that facts can be completely disregarded in favor of your opinions. Hopefully these arguments drive the new to towing folk to learn the facts for themselves and ignore quick answers on RV forums.
Well, just like your 'opinions' ours are also facts.

I encounter towing 'physics' every time we tow. And I can PROVE that whatever wrong things you two trolls think I have done, my towing 'theories' can be proven and as such are FACTS.

Bob
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Old 01-21-2020, 07:27 AM   #347
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There almost seems to be a deliberate attempt to downplay or even hide the oversteer/jackknifing problem. Certainly the hitch industry doesn't want you to know about it because their weight distribution hitches make the problem worse.
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Old 01-21-2020, 10:05 AM   #348
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There almost seems to be a deliberate attempt to downplay or even hide the oversteer/jackknifing problem. Certainly the hitch industry doesn't want you to know about it because their weight distribution hitches make the problem worse.
Yea, your right on, OOS! No one here understands how an experienced idiot like yourself keeps inserting himself to this discussion...Maybe the hitch industry is taking us all for a ride...but we like the results, so we will continue to use what we believe works for us...now please, find another thread to annoy folks on! Most of us here are trying to share our experiences with those who are new...not argue with those who just want to troll discussions...
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Old 01-21-2020, 02:11 PM   #349
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So I think it's pretty clear now that weight distribution, sometimes known as FALR (front axle load restoration), should be kept to a minimum in order to avoid oversteer and jackknifing in a hard swerve maneuver. Also try to keep the distance from the axle to the hitch ball as small as possible. Some hitches can add over a foot to that distance compared to a simple ball mount. Keep away from those. They will provide the leverage to enable your trailer to push your tow vehicle off the road.
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Old 01-21-2020, 02:27 PM   #350
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I'll repeat my question. If (for the sake of argument) I dont need AS or WD if my tow vehicle is big enough... then what is big enough? Not in charts but in reality.

What is big enough to tow a 7600 lbs Flying Cloud?
What is big enough to tow a 10,000 lbs Classic?

What does this "get s big enough rig" look like in real life?
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Old 01-21-2020, 02:38 PM   #351
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So I think it's pretty clear now that weight distribution, sometimes known as FALR (front axle load restoration), should be kept to a minimum in order to avoid oversteer and jackknifing in a hard swerve maneuver. Also try to keep the distance from the axle to the hitch ball as small as possible. Some hitches can add over a foot to that distance compared to a simple ball mount. Keep away from those. They will provide the leverage to enable your trailer to push your tow vehicle off the road.
Someone put this poor soul on the path to glory, bless his little ❤️.

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Old 01-21-2020, 02:42 PM   #352
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Weight distribution and anti sway equipment?

Yup. Hear you and know exactly what you mean...I’ve lived in the Deep South before.
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Old 01-21-2020, 02:59 PM   #353
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In real life you can tow a 7600 lb trailer on the ball with a heavy duty pickup. You will not overload the rear axle, your trailer won't sway, and you will have maximum stability against jackknifing.

You can use the stability chart as a guide keeping in mind that it's an example and it doesn't cover everything related to stability. I find the numbers they give to be reasonable. I pull a 7600 lb trailer with a Ram 2500. This combination falls inside the stability triangle.

For a 10,000 lb trailer your tow vehicle should be more than that. I know most people won't have such a truck. They have to compensate by driving slower than normal.
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Old 01-22-2020, 05:44 AM   #354
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Originally Posted by Dirtbeard View Post
I'll repeat my question. If (for the sake of argument) I dont need AS or WD if my tow vehicle is big enough... then what is big enough? Not in charts but in reality.

What is big enough to tow a 7600 lbs Flying Cloud?
What is big enough to tow a 10,000 lbs Classic?

What does this "get s big enough rig" look like in real life?
Maybe I missed it, but why not use a weight distribution hitch? I do not buy into some of the posts above about a weight distribution hitch manufacturer conspiracy. I think they help. So if they do help, why not use one? I just pull a 23FB. I’ve never pulled it without a weight distribution hitch.
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Old 01-22-2020, 06:12 AM   #355
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A weight distribution hitch is used when the trailer tongue weight causes the tow vehicle rear axle to overload. It should not be considered a safety device. The proper solution is to get a larger tow vehicle or a smaller trailer so that axle overloading does not occur.
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Old 01-22-2020, 07:04 AM   #356
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When I had my 2007 Mercedes modified by CanAm in London, Ontario to support my Hensley Arrow hitch, they also cut about five inches off the "stinger" bringing the trailer closer to the car. They also slightly bent the stinger to preload the arms with less screw jack travel.

I towed the new 2013 25FB International Serenity (had only full fresh water and propane and my brief case in it) home to the Phoenix area from Los Angles on I-10 and had no issues with the climb out up the mountains or descents. I drove at 55 mph the entire trip. Once I passed into Arizona, the 55 mph truck/towing speed limit of California expired. The trucks blew past me at the posted 75 mph plus some. No sway issues.

That Hensley hitch was retained when we traded the 25FB in on our 2014 31' Classic. By then I had upgraded to a 2012 Ram 2500HD with a Cummins diesel. We went with the second generation Jim Hensley design called the ProPride. Properly setup, there are no issues.

The Hensley is reused on our 2015 23D International Serenity using the same 2007 Mercedes. I upgraded the 23D to 15" wheels and Michelin tires (same size tires I had put on the 25FB) on the dealers lot, so the trailer was at the same elevation as the 25FB. Reused the same settings. That is a better fit for towing with our Mercedes at 55 mph.

One must do due diligence maintenance on the whole towing scene that also includes the hitch system.

We are not in a race when towing. The faster one drives, the less relaxing the trip becomes.
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Old 01-22-2020, 07:18 AM   #357
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A weight distribution hitch is used when the trailer tongue weight causes the tow vehicle front axle to be unloaded over its static condition. It is a safety device.
Fixed it for ya!
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Old 01-22-2020, 07:24 AM   #358
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Fixed it for ya!
Makes a lot more sense now..
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Old 01-22-2020, 07:36 AM   #359
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A weight distribution hitch is used when the trailer tongue weight causes the tow vehicle rear axle to overload. It should not be considered a safety device. The proper solution is to get a larger tow vehicle or a smaller trailer so that axle overloading does not occur.
Towing physics is stranger than we think, only thinking doesn't have to be strange.

This thread goes back to 2017!

I disagree that you only need a WDH when overloaded - overloaded is exceeding RAWR. When you need one is based on far more parameters than exceeding RAWR. Such as when the trailer exceeds 50% of tow vehicle weight or when a certain gross trailer weight - required by truck maker or by law. With no WDH I would have beaucoup traction but uncomfortable understeer. Not only understeer but drastically reduced braking, since the front end applies the majority of braking force... been there done that and got the tee shirt. My conclusion is that I will have one on any Airstream I ever tow. The trailer at gross weight is heavier than my F150 and there is no issue at all.
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Old 01-22-2020, 08:35 AM   #360
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Maybe I missed it, but why not use a weight distribution hitch? I do not buy into some of the posts above about a weight distribution hitch manufacturer conspiracy. I think they help. So if they do help, why not use one? I just pull a 23FB. I’ve never pulled it without a weight distribution hitch.
I'm definitely with the majority on this. I have yet to get a unit, but I can't imagine setting up a rig without AS and WD. I just asked the question "for the sake of argument" - meaning, I'm no engineer or physicist, so it helps me to know what they mean by "Get a big enough truck" when I see what that really means in the real-word.

IOW, given specific examples of trailer length and weight, (in their opinion) just what is a big enough rig to not need AS and/or WD? Helps me understand the argument in real-world terms.
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