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Old 10-27-2014, 11:16 AM   #1
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Best Weight Distribution hitch?

Question for those of you towing 34' Airstreams: What is the best weight distribution hitch to handle the 1,700 lb. hitch weight on my 2002 34' with slide? Is it unrealistic to expect a WD hitch to actually distribute the weight equally between the front and rear axles (along with a little to the trailer...)? Sway control is also a factor, but without proper weight distribution it is a moot point...
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Old 10-27-2014, 11:33 AM   #2
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Weight distributing hitches do not distribute weight evenly. That is a mathematical impossibility because of the number of variables in the configuration of ones rig.

What you want a WD hitch to do is move enough weight to the front axle of the tv to return the front end to as close as possible to the original steering geometry. This will vary widely depending hitch weight, tv size, tv spring pack, trailer length, and tongue weight.

The theory of 1/3, 1/3, 13 is an urban myth.

What are you towing with?
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Old 10-27-2014, 12:17 PM   #3
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Originally Posted by pjtaia View Post
What is the best weight distribution hitch to handle the 1,700 lb. hitch weight on my 2002 34' with slide? ...
Oh boy! Here we go again.... You will get many opinions of what is "the best" weight distribution hitch, and there are many threads on this forum for you to read. Almost everyone will have an opinion, and some of them will actually be factual, for the most part.

The thing is, "the best" for one person/rig, may not be the best for another. The pivot point projection hitches like the Hensley and the ProPride are generally thought of today as being the best, but they also have bad points such as their cost, complexity, weight, and sometime difficulty in hitching up.

I do suggest you study the "which is best" weight distribution threads, and decide what would be best for you. I will tell you it is my opinion that the selection of weight range of the hitch, and the actual setup of the WD hitch is more important than the brand or model. With the exception of one hitch that I know of that absolutely won't distribute that much weight, they all pretty much work the same.

Good luck with your choice and setup.
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Old 10-27-2014, 12:18 PM   #4
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Phil,

Still having trouble setting up your new trailer?

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Quote:
Originally Posted by pjtaia View Post
Question for those of you towing 34' Airstreams: What is the best weight distribution hitch to handle the 1,700 lb. hitch weight on my 2002 34' with slide? Is it unrealistic to expect a WD hitch to actually distribute the weight equally between the front and rear axles (along with a little to the trailer...)? Sway control is also a factor, but without proper weight distribution it is a moot point...
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Old 10-27-2014, 03:44 PM   #5
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Originally Posted by pjtaia View Post
Question for those of you towing 34' Airstreams: What is the best weight distribution hitch to handle the 1,700 lb. hitch weight on my 2002 34' with slide? Is it unrealistic to expect a WD hitch to actually distribute the weight equally between the front and rear axles (along with a little to the trailer...)? Sway control is also a factor, but without proper weight distribution it is a moot point...
On this forum, we frequently see "distribute the weight equally" used in three different ways:
1) having equal gross weights on both the front and rear axles, or
2) having equal net load added to the front and rear axles after hitching with WD applied, or
3) having equal net load added to front axle, rear axle, and TT's axles (so called "1/3,1/3,1/3" distribution).
Since you referred to "transferring a little to the trailer", I will assume you are using the second definition.

Yes, it is mathematically possible for a WDH to add equal amounts of load to the TV's front and rear axles.
There are three variables which determine how the load gets distributed -- a = TV wheelbase, b = ball overhang, and c = distance from ball to mid-point between between/among TT's axles.
To get equal load added to the front and rear axles, you need to adjust the WDH so the fraction of load added to the TT's axles is:

f = (a+2b)/(a+2b+2c)

For your 2005 Yukon XL, we could estimate the following: a = 130" and b = 65". And, for your 34' AS, I'll assume the value of c to be 260" (for mathematical convenience).
Those values would give f = (130+130)/(130+130+520) = 1/3.
So, it is mathematically possible (given the right combinations of a,b,c) not only to have equal front and rear added loads but also to have a 1/3,1/3,1/3 distribution.

HOWEVER, tests conducted for the US DOT-NHTSA and reported in 1977 (see this thread for details) concluded that adding load to the TV's front axle, in excess of the unhitched load, was not advisable from a directional stability point of view.

The Owners Manual for your 2005 Yukon also specifies that the WDH should be adjusted to return the front-end height to the unhitched value -- implying the "before" and "after" axle loads should be the same.

So, even though it might be possible to actually distribute the weight equally between the front and rear axles, there are credible sources which indicate it is not advisable to do so.
OTOH, since your 1700# TW probably exceeds the max TW specified in the Owners Manual, you might need to distribute some load to the front axle to prevent overloading of the rear axle -- only a trip to a scales will tell for sure.

As for choice of WDH -- you might want to consider a Reese 1700# Strait-Line Trunnion Bar WDH with integrated sway control.

Ron
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Old 10-27-2014, 05:02 PM   #6
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The theory of 1/3, 1/3, 1/3 is an urban myth.
Howie.

The 1/3 formula was discover at great length, in 1970, by repeated actual weight tests and highway handling tests, by using several different Airstreams and several different tow vehicles.

I would think that loading a cars trunk with 1000 (one thousand) pounds of weight, would have a very negative effect on the handling of that vehicle, when by itself.

If that then is the case, loading a cars rear end with the same 1000 pounds of weight from a load equaling hitch, and not moving a good portion of the weigh forward, will also create negative handling.

Equal loading or near equal loading on a cars 4 wheels, is a must, so that the designed handling is not compromised.

Or, lets take a half ton truck and put 1000 pounds payload in it, back as close to the rear bumper as possible. That for sure, will have some negative effect on the handling. Then is we move that same weight half way between the front and rear tires, the handling becomes much more positive.

Lastly, a much heavier rear end will cause a loss of control, as soon as you turn the steering wheel side to side.

Basic Physics.

Andy
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Old 10-27-2014, 05:56 PM   #7
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Anyone who ever played on a seesaw with someone of a different weight may not be able to mathematically explain the effects but will clearly understand that the 1/3 formula is an impossibility.
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Old 10-27-2014, 05:59 PM   #8
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WD hitch

I was curious if anyone has ever configured their Airstream to a gooseneck style hitch. The best towing trailer I ever had was a 36ft gooseneck that we hauled all over the country racing out of. The ball was 6 inches in front of the rear axle, and there was virtually no sway. It wouldn't be that hard to fabricate a frame to attach to the Airstream frame and come up and over the bed of the truck. That would be the best wd hitch, I think. Just thinking out loud, Mike
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Old 10-27-2014, 08:11 PM   #9
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Anyone who ever played on a seesaw with someone of a different weight may not be able to mathematically explain the effects but will clearly understand that the 1/3 formula is an impossibility.
Howie.

What's your theory?

Andy
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Old 10-27-2014, 08:46 PM   #10
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I was curious if anyone has ever configured their Airstream to a gooseneck style hitch. The best towing trailer I ever had was a 36ft gooseneck that we hauled all over the country racing out of. The ball was 6 inches in front of the rear axle, and there was virtually no sway. It wouldn't be that hard to fabricate a frame to attach to the Airstream frame and come up and over the bed of the truck. That would be the best wd hitch, I think. Just thinking out loud, Mike
That is what the pivot point projection hitches do. They simulate the point of rotation somewhere on or forward of the rear axle of the tow vehicle.
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Old 10-27-2014, 09:10 PM   #11
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Originally Posted by pjtaia View Post
Question for those of you towing 34' Airstreams: What is the best weight distribution hitch to handle the 1,700 lb. hitch weight on my 2002 34' with slide? Is it unrealistic to expect a WD hitch to actually distribute the weight equally between the front and rear axles (along with a little to the trailer...)? Sway control is also a factor, but without proper weight distribution it is a moot point...
Hi - just curious - what is your hitch receiver's max capacity? I have a 2013 Chevy 3/4 ton truck with a 2.5" receiver with a max weight of 1500#. Even if you have the same max on your receiver, you'd be more than 10% over there...

Ron G gave your excellent insights for your specific questions. Good luck!
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Old 10-27-2014, 09:30 PM   #12
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The 1/3 formula was discover at great length, in 1970, by repeated actual weight tests and highway handling tests, by using several different Airstreams and several different tow vehicles.
Quote:
If you have 900 pounds tongue weight, 300 should go back to the trailer axle/axles and 600 should go to the tow vehicle, with 1/4 of that weight on each wheel of the tow vehicle.

That was established decades ago.

Not adding weight to the front axle, or removing weight from it, is BEGGING for a sway and loss of control.

GUARANTEED

Insurance company data proved so, almost a half of a century ago.
Without proper documentation of test conditions and data analysis, there is no proof -- only unsubstantiated opinions.

Proper documentation of properly-planned and properly-conducted testing does exist in the form of a report prepared for the US DOT-NHTSA in 1977.
Conclusions from the report are discussed in this thread.
The study concluded that:

“---hookups resulting in a small hitch-low attitude (corresponding to 0 percent hitch load transfer to the front axle in conventionally sprung tow cars) is more desirable than a level attitude which provides approximately 25 percent hitch load transfer.”

IOW, adjusting the WDH to restore the front axle to its unhitched load (a.k.a. 100% Front Axle Load Restoration) is more desirable than adjusting the WDH so that a net load equal to 25% of TW is added to the front axle.
This finding, and perhaps similar findings from yet undiscovered test programs, could explain why Ford, GMC/Chevrolet, Toyota, Progress Mfg. Inc. (Equal-i-zer), and Reese now are specifying that a WDH be adjusted to give 100% (or even 50%) FALR rather than using the old recommendation based on “equal squat”.

Quote:
I would think that loading a cars trunk with 1000 (one thousand) pounds of weight, would have a very negative effect on the handling of that vehicle, when by itself.

If that then is the case, loading a cars rear end with the same 1000 pounds of weight from a load equaling hitch, and not moving a good portion of the weigh forward, will also create negative handling.
Nobody has said a WDH should not be used to transfer load to the front axle.
When a 1000# tongue weight is applied to the ball with no WD applied, a load of approximately 500# will be removed from the front axle, and 1500# will be added to the rear.
The WDH should be adjusted to transfer about 500# to the front axle -- removing about 750# from the rear axle and adding about 250# to the TT's axles in the process.
The resulting NET change in axle loads is approximately 0# added to the front axle, 750# added to the rear, and 250# added to the TT's axles.

Quote:
Equal loading or near equal loading on a cars 4 wheels, is a must, so that the designed handling is not compromised.
This is another unsubstantiated opinion.
Furthermore, adding 333# to the TV's front axle and adding 333# to the rear axle is no guarantee that the front and rear will be equally or nearly equally loaded.

Quote:
Or, lets take a half ton truck and put 1000 pounds payload in it, back as close to the rear bumper as possible. That for sure, will have some negative effect on the handling. Then is we move that same weight half way between the front and rear tires, the handling becomes much more positive.
A load of 1000# placed between the axles and tailgate might remove about 150# -- not too likely to have a significant negative effect.

Quote:
Lastly, a much heavier rear end will cause a loss of control, as soon as you turn the steering wheel side to side.
If you add 1500# to the rear axle of a 1/2 ton truck, you might end up with 3500# on the front axle and 3800# on the rear -- probably not going to cause loss of control as soon as you turn the steering wheel side to side.

Basic Physics.

Ron
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Old 10-27-2014, 09:40 PM   #13
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Howie.

What's your theory?

Andy
It is not my theory, I yield to Archimedes. He figured it out long before the WD hitch.

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Old 10-27-2014, 09:48 PM   #14
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Howie.

What's your theory?
It really doesn't matter whether a "1/3,1/3,1/3" distribution is possible.

What does matter is -- adding a load equal to 1/3 of tongue weight to the front axle significantly increases the tendency for oversteer which can lead to loss of control.

Ron
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