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Old 10-04-2008, 11:44 PM   #1
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how does tongue weight capacity rating affect handling?

My tongue weight is about 500 lbs so I was looking for a weight distribution hitch that was rated to at least 600 lbs. I found a good deal on one but it is rated to 1000 lbs. What will be the difference if I use this hitch instead of the one that is rated at a lower weight? If the difference is negligible I'd like to buy it. My dual axle trailer weighs about 5k.
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Old 10-04-2008, 11:54 PM   #2
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My tongue weight is about 500 lbs so I was looking for a weight distribution hitch that was rated to at least 600 lbs. I found a good deal on one but it is rated to 1000 lbs. What will be the difference if I use this hitch instead of the one that is rated at a lower weight? If the difference is negligible I'd like to buy it. My dual axle trailer weighs about 5k.
The rating of the hitch bars (torsion bars) that are proper, is a function of the tongue weight AND the tow vehicle spring rate.

Over hitching by using bars that are too heavy, can cause many damages to the trailer, as well as stiffen the tow vehicle ride.

Exactly what tow vehicle do you have?

Andy
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Old 10-05-2008, 12:39 AM   #3
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2000 Ford F-150 long bed 4X4. My trailer is a 1961 Avion T-27 that weighs about 5k fully loaded.
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Old 10-05-2008, 10:47 AM   #4
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2000 Ford F-150 long bed 4X4. My trailer is a 1961 Avion T-27 that weighs about 5k fully loaded.
The 150 would dictate 750 pound bars.

But when you added the 4 X 4, then you changed the requirement to 550 or 600 pound bars.

The 1000 pound bars that you had a deal on, quite well would be OK, but not for your rig, under any circumstances.

Andy
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Old 10-05-2008, 02:08 PM   #5
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Andy,

If, like "Smokey" says, his trailer's tongue weight is 500 pounds, why would he need bars any heavier than the ones rated for 500 pounds, irrespective of the tow vehicle?

I distinctly remember you recommending in other threads people use 500 pound bars with trucks pulling trailers with tongue weights of up to 1000 pounds.
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Old 10-05-2008, 03:11 PM   #6
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The 1000 pound bars that you had a deal on, quite well would be OK, but not for your rig, under any circumstances.
Andy
I'm having trouble understanding this sentence. So are you saying the 1000 pound bars would be ok but not ideal?
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Old 10-05-2008, 03:16 PM   #7
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Andy,

If, like "Smokey" says, his trailer's tongue weight is 500 pounds, why would he need bars any heavier than the ones rated for 500 pounds, irrespective of the tow vehicle?

I distinctly remember you recommending in other threads people use 500 pound bars with trucks pulling trailers with tongue weights of up to 1000 pounds.
Steve.

Smokey says "about 500 pounds"

I think that is a guess.

But then, 500 pounds "when"?

Empty, loaded, full of water, full of propane (and what size tanks ?), clothes, grocerys, toys?

Then what year trailer? He does say he has a tandem axle trailer.

Seldom will you find a 500 pound tongue weight on an Airstream, unless it is perhaps a Bambi, or grossly mis-loaded.

Then how about his 4 X 4 ?

Andy
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Old 10-05-2008, 03:26 PM   #8
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... What will be the difference if I use this hitch instead of the one that is rated at a lower weight?...
does the hitch incorporate sway control with the w/d-spring bars?

IF it does the bars need to flex a given amount for the friction/sway control to function.

1000 lb bars may not flex much with a 500 lb tongue, which would reduce sway control.

really much of this depends on the EXACT TYPE of hitch (do u know brand/model?) ...

and an accurate measure of tongue weight.

and how much u intend to tow,

and how much STUFF is in the truck bed...

and so on.

cheers
2air'
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Old 10-05-2008, 03:57 PM   #9
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does the hitch incorporate sway control with the w/d-spring bars?

IF it does the bars need to flex a given amount for the friction/sway control to function.

1000 lb bars may not flex much with a 500 lb tongue, which would reduce sway control.

really much of this depends on the EXACT TYPE of hitch (do u know brand/model?) ...

and an accurate measure of tongue weight.

and how much u intend to tow,

and how much STUFF is in the truck bed...

and so on.

cheers
2air'
I was leaning towards this Curt system because they are based in my town. It comes in three models: 600, 800 and 1000.

http://www.curtmfg.com/index.cfm?event=prodetail&id=65&categoryid=36

and for sway control

http://www.curtmfg.com/index.cfm?event=prodetail&id=67&categoryid=36

I will have at least 300 lbs in the back of my truck so do I need to add that figure to the actual trailer tongue weight?

The tongue weight is fairly accurate. It should be between 500-600 lbs. When I purchased the trailer the guy had a scale and when he weighed it it was 450 lbs but that was empty. This trailer is a 61 Avion 27 footer. The factory weight is listed at 3800 lbs. Avions were rather light in the early years and have different frames then airstreams. Fully loaded I suspect it will be between 5-6k.

I will be towing it from Wisconsin to Portland, Oregon in three weeks. I will be full timing in it for six months.

Thanks for your help.

Smoky
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Old 10-05-2008, 04:13 PM   #10
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...I will have at least 300 lbs in the back of my truck so do I need to add that figure to the actual trailer tongue weight?...
it's not a matter of adding bed payload to tongue weight (except for staying within the ratings)...

but understanding that how much payload and WHERE in the bed it is can affect handling and weight distribution....

so the sway control u are considering is a friction add-on outrigger...

you may catch a lotta crap here for considering that approach.

the curt comes as either a "round bar" or trunnion style...

i think on the round bar version, spring bars are interchangeable...

my choice would be the 800 lb bars, knowing upgrading just the bars is an option.

not sure about the trunnion style, usually those bars/heads are not interchangable, but check with curt.

make sure u have fresh tires and a spare or 2 for this trip.

the tires may have a greater impact on the towing experience, than the hitch in this situation.

so back to your original question, IF u have a good deal on a 1k unit, go with it.

cheers
2air'
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Old 10-05-2008, 06:10 PM   #11
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My tongue weight is about 500 lbs so I was looking for a weight distribution hitch that was rated to at least 600 lbs. I found a good deal on one but it is rated to 1000 lbs. What will be the difference if I use this hitch instead of the one that is rated at a lower weight? If the difference is negligible I'd like to buy it. My dual axle trailer weighs about 5k.
Smoky, the amount of force which must be applied to the WD bars depends on how much load you wish to transfer. A common WD objective is to return the steer axle load to the unhitched value.

With your TV and TT, each WD bar needs to have an applied force equal to about 80% of the tongue weight to achieve the above objective. Therefore, if your TW is 500#, each bar should have an applied force of about 400#. This could be achieved with any of the bar ratings you have mentioned. The difference is that, under a given loading, a higher rated bar does not "flex" as much as a lower rated bar.

A potential problem with using a higher rated bar (i.e. one which is too "stiff") could arise when crossing a dip where the front of the TV is higher than its rear and the rear of the TT is higher than its front. In this situation, the hitch will try to force the rear ends of the WD bars down and the TT's A-frame will try to lift the bars up. This can result in a significant increase in the force applied to the WD bars and, hence, the force applied to the A-frame.

It's hard to say whether the 1000# bars could cause damage. However, if the TW is only 500# and your WD objective is to return the steer axle load to the unhitched value, I would go with the 600# bars.

Ron
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Old 10-05-2008, 06:53 PM   #12
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The rating of the hitch bars (torsion bars) that are proper, is a function of the tongue weight AND the tow vehicle spring rate.

Andy
Wouldn't the 3rd be the wheel base of the vehicle?

It seems that it would be much easier to transfer weight forward on a short wheel based vehicle than a long wheel based vehicle. In other words a lighter rated bar may be used on the short wheel based vehicle.
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Old 10-06-2008, 05:29 PM   #13
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Wouldn't the 3rd be the wheel base of the vehicle?

It seems that it would be much easier to transfer weight forward on a short wheel based vehicle than a long wheel based vehicle. In other words a lighter rated bar may be used on the short wheel based vehicle.
If your objective is to return the steer axle load to its unhitched value, the required force on the WD bars is not a function of the TV's wheelbase.

You are correct that it is easier to transfer load forward on a short wheelbase. However, it is also easier for the tongue weight to remove load from the front axle when the wheelbase is shorter.

If you have wheelbase = 140", drive axle to ball = 70", ball to TT axle center = 210", and tongue weight = 500#:

Application of TW on the ball without WD would cause the steer axle load to be reduced by 500#*(70"/140") = 250#

If the WD system then transfers 125# to the TT axles, the steer axle load would then be reduced by 125#*(70"+210")/140" = 250#.

If the wheelbase in the above example is reduced to 100":

Application of TW on the ball without WD would cause the steer axle load to be reduced by 500#*(70"/100") = 350#

If the WD system then transfers 125# to the TT axles, the steer axle load would then be reduced by 125#*(70"+210")/100" = 350#.

So, with the shorter wheelbase, more load is removed from the steer axle and it is easier for the WD system to transfer load back to the steer axle. The wheelbase effects cancel each other. The required force on the WD bars remains the same.

Although, given the above objective, the required WD bar force is not a function of TV wheelbase, the required WD bar force is a function of:

Tongue Weight,
Distance from drive axle to ball,
Distance from ball to TT axle center, and
Effective length of the WD bars.

Ron
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