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Old 08-31-2008, 01:07 PM   #1
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W/D question

OK, I am having trouble figuring out what is right on what is the actual tongue weight put on the TV after connecting it all up. Below is a quote from the Airstream manual:

Quote:
When a trailer is hitched up properly to a tow vehicle with a load equalizing hitch, approximately 1/3 of the trailer's tongue weight will be on the trailer's axles and 2/3 will be transferred to the tow vehicle, 1/3 of this weight transfer will be carried by the front wheels and 1/3 by the rear wheels of the tow vehicle (See diagram), Thus, the tire load of each wheel on the tow vehicle will be increased by 1/6 of the trailer's tongue weight. The tire air pressure of the tow vehicle should be increased to compensate for this additional weight. Refer to the vehicle's owner’s manual for this information.
If I am understanding this right, if you have a tongue weight of 900 lbs, after you connect it up correctly, you end up with 595 lbs on the TV and 306 added back to the trailer weight?

This is very confusing any help on understanding this is appreciated.

Bob
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Old 08-31-2008, 01:55 PM   #2
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Originally Posted by RLS View Post
OK, I am having trouble figuring out what is right on what is the actual tongue weight put on the TV after connecting it all up. Below is a quote from the Airstream manual:

If I am understanding this right, if you have a tongue weight of 900 lbs, after you connect it up correctly, you end up with 595 lbs on the TV and 306 added back to the trailer weight?

This is very confusing any help on understanding this is appreciated.

Bob
That's sort of correct.

The 2/3 of the weight transfered to the tow vehicle (600 pounds) should be divided equally between the front and rear axle of the TV, or in this case 50% to each.

The 1/3 and 1/3 on the tow vehicle only makes sense, if you refer back to the original 900 pounds.

That weight distribution, becomes as perfect as you can get.

The next question, that the manual does not cover, is that the tongue of the trailer must easily bounce, within reason, for proper control.

Over hitching, bars that are way too heavy duty, can also transfer the correct amount of weight, but they will not bend as they should, which in turn will not provide the soft ride that Airstream trailers demand, or else.

Andy
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Old 08-31-2008, 04:00 PM   #3
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I always just made sure the whole rig was level and the ball was at 19.5 inches and I have always been fine. 10 percent on the pin keeps it from swaying
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Old 08-31-2008, 07:14 PM   #4
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w/d spring bar length

I get the distribution to all the wheels but there is another part of the w/d puzzle that I have often wondered about. Are all spring bars the same length?

Since the hitch and w/d setup has to be adjusted to fit an individual trailer and TV, is it acceptable for the spring bars to be shortened if that is the only way to get a vertical hang on the chain? For instance, say you couldn't move the brackets back any further due to gas bottles, battery location or whatever.

How would you fix it if it's not good to shorten it?

Inquiring mind,

TB
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Old 08-31-2008, 07:22 PM   #5
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I always just made sure the whole rig was level and the ball was at 19.5 inches and I have always been fine. 10 percent on the pin keeps it from swaying
There is NO correct ball height, except your trailer.

Ball height is a function of how good the axle may be, it's starting angle, and the load in "your" trailer, plus the year of the trailer.

All of those can and do change the ball height.

Some people ask "what should the ball height be," only to find out their trailer is not level as it should be, if they use as an example 19.5 inches.

The factory ball height in the manuals, is for a brand new trailer, with zero payload.

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Old 08-31-2008, 07:29 PM   #6
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Originally Posted by tinbender View Post
I get the distribution to all the wheels but there is another part of the w/d puzzle that I have often wondered about. Are all spring bars the same length?

Since the hitch and w/d setup has to be adjusted to fit an individual trailer and TV, is it acceptable for the spring bars to be shortened if that is the only way to get a vertical hang on the chain? For instance, say you couldn't move the brackets back any further due to gas bottles, battery location or whatever.

How would you fix it if it's not good to shorten it?

Inquiring mind,

TB
What brand hitch do you have? If the chain is attached to the end of the bar, then you must use it that way. Or, if it's a Reese, then add the dual cam to the bars. Then it doesn't matter if the chains are vertical or not.

DO NOT attempt to shorten the bars.

If, when in a straight line, the chains are not vertical as they must be, then you can move the LPG tanks and the tank bracket.

Load equalizing bars, torsion or bend, MUST NEVER BE REDUCED, when traveling.

When the chains are not vertical, then as you make a turn, one bar will bend more and the other bar will bend less. That is not a good situation.

As you turn, both bars must increase the stress on them.

Andy
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Old 08-31-2008, 08:14 PM   #7
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Andy,

From what I have been reading on here, you are the man! Your reply is the one I had hoped for. So my understanding is right from what you have stated. I also have been reading your replies as to what weight bars to get, so my 1,200 lbs. ones are sitting on the shelf (new) with the 800lbs. ones now ready to hook up. I'm still unsure if these are too much from what you have been talking about. I will be doing the bounce test to see! LOL Just so you know, (I know I am going to get blasted for this) I have an Infiniti QX56 SUV that will be hauling a 2004 25 classic. Load capacity of the QX56 is 1,274lbs (passengers and cargo). QX56 GVWR is 7,100lbs. and a Gross Combined weight (SUV and trailer) of 14,822lbs. Tongue weight is right around 875Lbs. and GVWR of trailer is 7,300lbs., dry is 6,050lbs.
I know this not an ideal set-up, but it will have to due. My main concern was the 1,274lbs. part. but since only roughly 600lbs. tongue weight is actually going onto the SUV, I am OK. Passengers and cargo will be no more than 500Lbs.

Thanks again for the reply

Bob
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Old 08-31-2008, 08:23 PM   #8
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spring bar length

Andy,
Thanks for the good info. I have a Reese but I'm not referring to mine. I just wondered about the bars because each hitch setup seems to be unique to each trailer and TV. That being the case, I didn't know if there is a standard length based on tongue length or some other chosen measurement. In looking at different systems on manufacturer's websites I have never seen bar length specified.

Always something to learn.
Thanks again,

TB
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Old 08-31-2008, 09:36 PM   #9
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Andy does have some good info, I have learned alot today from him. I think I am going to start drinking Pineapple juice, and listening to Hawian music.
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Old 08-31-2008, 09:42 PM   #10
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Andy does have some good info, I have learned alot today from him. I think I am going to start drinking Pineapple juice, and listening to Hawian music.
MAHALO

But if you want really enjoy the music, it's Hawaiian. LOL

Andy
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Old 09-01-2008, 02:54 PM   #11
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I believe the 1/3, 1/3, 1/3 tongue weight distribution "guideline" is one of those towing myths which sounds good; but seldom, if ever, is actually achieved. And, such a distribution, if it could be achieved, probably is not desirable.

Some TV manufacturers specify that the WD system should be adjusted so that the front of the TV is returned only to the unhitched height. This implies that the load on the front axle should be returned only to its unhitched load. I.E., none of the tongue weight should be on the front axle.

Many reports of measured axle loads suggest that, after application of weight distribution, the tongue weight is more likely to be distributed about 0%/75%/25% on the front axle, rear axle, and TT axles respectively. Very few people have been able to get more than about 10% of tongue weight transferred to the front axle.

If one considers that a typical TV might have its front/rear axle load at 55%/45% before the TT is attached, then having the tongue weight equally distributed to the front and rear axles would not produce the recommended equal front/rear axle load when towing (which might be another towing myth).

A 1/3, 1/3, 1/3 distribution only is possible for some very specific combinations of TV wheelbase, TV ball overhang, and TT ball to axle distance. More realistically, if you had a TV wheelbase = 130", ball overhang = 65", and ball to TT axles = 195" (just to pick some easy numbers), you would need to transfer 40% of the tongue weight to the TT axles in order to get an equal 30%/30% on the TV's front and rear axles.

A WD system probably cannot (and, should not) transfer more than about 30% of the tongue weight to the TT axles. In this case, and for the above dimensions, the net result after WD is applied would be to have a tongue weight distribution of 10%/60%/30%.

If the WD system transferred 25% to the TT axles, the net distribution would be 0%/75%/25%.

Many people have reported being quite frustrated when trying to achieve a 1/3, 1/3, 1/3 distribution or even just an equal distribution of tongue weight to the TV's front and rear axles. For the vast majority of TV/TT combinations, neither of these objectives can be achieved.

Ron
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Old 09-01-2008, 03:02 PM   #12
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I think the proper procedure starts with ball height in relation to the trailer when its level. Then when you connect the trailer the weight of the trailer pushes down on the rear of the TV. You then use WD to get the trailer back to level. Once you do that the weight will be properly distributed to the rear of the trailer and to the front axle on the TV.

But it starts with the proper ball height.

If this is not correct please correct my analogy.

My current setup has these results:

Front Axle 5240 lbs, Rear Axle 5200 lbs and the trailer 7540 lbs.

I have a 2000 Classic with a GVWR of 9800 lbs.

I have not weighed my truck without the trailer nor I have I weighed the trailer not connected to the truck.
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Old 09-01-2008, 03:11 PM   #13
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i agree the rule of 3rds is history if not myth.

it may have been important or useful in the sedan daze of towing when lifting the drive axle was possible...

or in the single axle short trailer era.

and it might be useful in learning how w/d gear works initially

but even then i see no evidence of it working neatly as suggested.

i've weighted my rig dozens of times with different w/d bar ratings...

and a variety of tensions ON those bars...

UNDER max bar flex and max bar rating, and with the trailer tongue bending under the stress...

only about 150-200 lbs of a 12-1400lb tongue mass shows up on the trailer axles.

what happens at the tv axles is greatly confused. that confusion is increased by NOT weighing the tv un hitched.

it should be obvious that 50/50 on the tv axles hitched isn't equal distribution of the tongue mass...

but it isn't obvious for most of us at first thought.

cheers
2air'
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Old 09-01-2008, 03:14 PM   #14
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Quote:
Originally Posted by 2airishuman View Post
...

it should be obvious that 50/50 on the tv axles hitched isn't equal distribution of the tongue mass...

but it isn't obvious for most of us at first thought.

cheers
2air'
Do you think its possible I may have my springs too tight? My F250 has a GCWR of 10,000 pounds.

My current setup has these results:

Front Axle 5240 lbs, Rear Axle 5200 lbs and the trailer 7540 lbs.

I have a 2000 Classic with a GVWR of 9800 lbs.

My trailer is level after adjusting the W/D and getting these weights.
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