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Old 01-10-2014, 12:41 PM   #1
DJW
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Figuring the right WD bars- 1000# or 1400#?

Hello all, I'm embarrassed, cuz I'm sure this has been covered before. Just can't find it in a search.

The facts:
  • My 25' Safari has a tongue weight of about 1040 lbs.
  • My '07 Tundra, with TRD suspension, has a pretty stiff ride. Tows the trailer great, never had a problem.
  • My current WD hitch has 1400# trunnion bars, which transfer the weight very well, even with only about 2" displacement after chains are tight. It seems to me to be pretty "stiff".
  • It's time for new hitch.

Thinking of getting basically the same hitch (Eaz-lift) but with 1000# bars. I'm hoping that might add a little cushioning, or ease some of the bumps etc. that get transferred to the AS.

Another possibility is a hitch with 1200# bars, I guess.

Appreciate any advice.

Thanks,

Don
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Old 01-10-2014, 01:00 PM   #2
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Eaz-lift if I remember correctly, uses round and tapered bars. Equal-I-zer uses square bars and Reese uses what they call trunion, or square tapered bars. In any event, 1000lb bars would seem like the right ones, or some might say even 800lb, depending on the brand/type of bars.
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Old 01-10-2014, 02:16 PM   #3
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Originally Posted by DJW View Post
Hello all, I'm embarrassed, cuz I'm sure this has been covered before. Just can't find it in a search.

The facts:
  • My 25' Safari has a tongue weight of about 1040 lbs.
  • My '07 Tundra, with TRD suspension, has a pretty stiff ride. Tows the trailer great, never had a problem.
  • My current WD hitch has 1400# trunnion bars, which transfer the weight very well, even with only about 2" displacement after chains are tight. It seems to me to be pretty "stiff".
  • It's time for new hitch.

Thinking of getting basically the same hitch (Eaz-lift) but with 1000# bars. I'm hoping that might add a little cushioning, or ease some of the bumps etc. that get transferred to the AS.

Another possibility is a hitch with 1200# bars, I guess.

Appreciate any advice.

Thanks,

Don
Don.

You need to use a rating bar that will not increase the stiffness of the tow vehicle.

I would suggest that you use a 600 pound bar, that has some decent resillience, like a Reese, but with full sway control.

We do not sell load equalizing hitches.

Andy
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Old 01-10-2014, 05:23 PM   #4
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Thanks Andy, I've appreciated your advice in the past, especially about trying to give the AS an easier ride.

Just what does the 600, or 1000, or 1400 mean? Amount of pounds the bars will maximally re-distribute? In which case, I would think folks would want bars that are 2/3 of the hitch weight, to move 1/3 to the front of the truck, and 1/3 to the trailer axles. Is that right??

Don
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Old 01-10-2014, 05:44 PM   #5
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Originally Posted by DJW View Post
Thanks Andy, I've appreciated your advice in the past, especially about trying to give the AS an easier ride.

Just what does the 600, or 1000, or 1400 mean? Amount of pounds the bars will maximally re-distribute? In which case, I would think folks would want bars that are 2/3 of the hitch weight, to move 1/3 to the front of the truck, and 1/3 to the trailer axles. Is that right??

Don
Don.

The numbers are the weight capacity of the 2 bars.

When a proper rated load equalizing hitch is properly installed AND properly adjusted the tongue weight, say 900 pounds, transfers 600 pounds to the tow vehicle and 300 pounds to the trailer axle or axles.

Physics does not change in time, although some would like it to change.

In 1970, when I worked for the insurance division of Airstream, Caravanner Insurance Company, we did a number of hitch studies.

For a larger Airstream the hitch bar rating for a car as a tow vehicle was 1000 pounds.

With that same trailer, the rating dropped to 750 pounds when a 1/2 ton truck was used.

Again, with that same trailer, the rating dropped to 600 pounds, when a 3/4 truck was used.

Those specs have stood their ground for over 40 years.

Additionally, the Airstream must have a soft ride. Using bars that are excessively rated, will and does cause many different damages to the trailer.

Damages happen for several reason, such as excessive rated tow vehicle, excessive rated hitch bars, out of balance running gear, and bad rubber rods in the torsion axle/axles.

It does not matter if the tongue weight is say 1000 pounds, what rating the torsion bars must be is determined by the tongue weight AND the duty rating of the tow vehicle. The heavier the duty of the tow vehicle, the lighter the bars must be.

Bottom line then is use the lightest bars that you can, which it part is dictated by the rigidity of the tow vehicle.

Some will argue, but thousands upon thousands of test miles were done starting in late 1969, which proved the above time and time again.

Hopes this answers your questions.

Andy
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Old 01-10-2014, 05:44 PM   #6
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I think you need a w.d. hitch with a slightly higher rating than the actual typical tongue weight of your Airstream. If not you may be limited on the amount of weight you can transfer causing lightened steering, poorer handling, overweight rear axle load, porpoising on some roadways, and headlights aimed too high for the safety of you and those approaching you at night.

Personally and it's just me, I suspect a light w.d. bar bent to it's maximum trying to transfer a heavier load than it's rated for, is less flexible than a properly sized bar partially bent with flexibility remaining.

It looks like Inland Andy makes a reasonable point in recommending lower rated bars for heavier trucks, but I don't think any Tundra has that heavy a spring rate and ability to carry a heavy load without good weight distribution.

Inland Andy has performed tests on weight distribution bars indicating tapered bars are the most flexible and gentle on your truck and trailer.
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Old 01-10-2014, 05:53 PM   #7
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This is a long time debated question. Doug and I disagree on this. My experimentation has led be to believe...GENERALLY... that when selective bars are available for an adequately rated head, that I would select bars one step BELOW the ACTUAL tongue weight of your loaded AS. Not all hitch manufacturers accommodate this.

For example with my Reese dual cam, I need a head rated at 10,000 pounds. Reese offers 600, 800, 1000# bars for that head. For my unit, 800 pound bars worked great! My loaded tongue weight is about 900 - 950#s on any given trip.

My Hensley has 1000# bars and I feel they are just a bit too stiff.
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Old 01-10-2014, 05:58 PM   #8
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Originally Posted by DJW View Post
Thanks Andy, I've appreciated your advice in the past, especially about trying to give the AS an easier ride.

Just what does the 600, or 1000, or 1400 mean? Amount of pounds the bars will maximally re-distribute? In which case, I would think folks would want bars that are 2/3 of the hitch weight, to move 1/3 to the front of the truck, and 1/3 to the trailer axles. Is that right??

Don
That is the eternal nagging question. I have contacted Reese, Equal-iz-er and Hensley with that question and got no answer. Additionally I am of the belief that no two manufacturers rate to any common standard. EQ is horribly stiff relative to their rating. Reese seems to cover the bases and Hensley, while offering a couple of ratings and a bushing change will accommodate some selectivity, they have nothing lower than 1000#s unless you go to the Cub model, which is way too light in the head mechanism for most ASes.
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Old 01-10-2014, 06:00 PM   #9
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That's interesting Rich because we have a ProPride with 1400# bars and it rides like a dream.

But the difference here, and it supports both our contentions as well as what Inland Andy has said in the past, is we have a 1/2 ton Ram truck with coil springs and you have a 3/4 ton truck with heavy duty leaf springs.
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Old 01-10-2014, 06:03 PM   #10
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Actually, I tow with a lot of vehicles. My 1/2 ton van, escalades, Yukon XLs, Avalanches, Suburbans up to 3/4 ton PU's. When trying to balance out my 1/2 ton with the Hensley, I ran into some issues in the front of the AS because I needed to apply more WD and the 1000# bars just weren't flexible enough. I was overloading the 1/2 ton van though.....not a correct SYSTEM.
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Old 01-11-2014, 07:05 PM   #11
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Quote:
Originally Posted by DJW View Post
  • My 25' Safari has a tongue weight of about 1040 lbs.
  • My '07 Tundra, with TRD suspension, has a pretty stiff ride. Tows the trailer great, never had a problem.
  • My current WD hitch has 1400# trunnion bars, which transfer the weight very well, even with only about 2" displacement after chains are tight. It seems to me to be pretty "stiff".
  • It's time for new hitch.

Thinking of getting basically the same hitch (Eaz-lift) but with 1000# bars. I'm hoping that might add a little cushioning, or ease some of the bumps etc. that get transferred to the AS.

Another possibility is a hitch with 1200# bars, I guess.

Appreciate any advice.
Don, the proper choice of WD bar rating depends on what you want the WD bars to accomplish.
If you want to try to achieve equal load added to front and rear of the TV, you'll need bars with a relatively high rating.
If you want to restore 100% of the load which was removed from the front axle (which, I believe, is what currently is recommended by the Tundra's manufacturer), you'll need bars with an intermediate rating.
If you want to restore only 50% of the removed load, bars with a relatively low rating will work.

The amount of load which can be returned to the front axle depends on:
TV wheelbase -- "D1",
TV ball overhang (distance from rear axle to ball) -- "D2",
Distance from ball coupler to midpoint between TT's axles -- "D3",
Amount of upward force applied to rear ends of WD bars, and
Effective length of the WD bars.

To get a quantitative estimate of proper bar rating, we need to know what a bar's rating means in terms of how much load can be applied to the rear end of a bar.
I've never seen a definitive statement from a WDH manufacturer, but I think it's safe to assume a bar with a rating of xxx# can withstand an upward force of xxx#.

Let's assume TV/TT/Bar dimensions D1 = 146", D2 = 65", D3 = 200", and D4 = 28".
A TW of 1040# applied to this TV would cause about 1040*65/146 = 463# to be removed from the front axle.
To restore 463# to the front axle would require a load of about 463*146/(65+200) = 255# to be transferred to the TT's axles.
To transfer 255# to the TT's axles would require each WD bar to be loaded to about (255*200/28)/2 = 911#.

Based on your 1040# TW and the estimated dimensions, it appears that 1000# WD bars would be more than adequate.
If you replace the estimated values with actual distances, you can get a refined estimate of how much bar force will be required.

Ron
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Old 01-11-2014, 07:59 PM   #12
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Wow! It's been 44 yrs since I did that kind of math. Wow! Thanks a 1,000,000. Wow!
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Old 01-11-2014, 08:53 PM   #13
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Ron Gratz, would trucks with the same dimensions but different springs (one heavy, the other light duty) still have the same results using your formula? That is, would a half-ton truck use the same w.d bar as a one-ton truck to achieve the same amount of weight distribution?

And if weight distribution is the only goal, why not use 1400# bars for every application?
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Old 01-12-2014, 11:37 AM   #14
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Ron Gratz, would trucks with the same dimensions but different springs (one heavy, the other light duty) still have the same results using your formula? That is, would a half-ton truck use the same w.d bar as a one-ton truck to achieve the same amount of weight distribution?
Yes, given the same dimensions, a half-ton truck and a one-ton truck would get the same amount of load transfer if the same amount of force were applied to the WD bars.

Quote:
And if weight distribution is the only goal, why not use 1400# bars for every application?
A more highly rated bar generally will be stiffer.
When the rear tires of a TV go through a low point, the stiffer bar will flex less and will apply more force to the TT's A-frame.
The potential for damage to the A-frame and trailer is greater if the bars are unnecessarily stiff.

Ron
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