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Old 07-22-2006, 06:42 PM   #1
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1978 31' Excella 500
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Which springs do I need?

I know this question has been asked a lot however its been a while.I read a resent post by andy at inland rv that states some people are adding to much spring to thier hitches.I can't remember where I saw it but it was a formula inwhich stated that a 3/4 ton truck would need 550# springs.Im not doing andys formula any justice and I do realize it matters how much tongue wieght you have.My question is this... Which springs do I need with a equal-izer brand, distribution hitch on a 06 GMC Sierra DuraMax crew cab pulling a 31' excella (loaded 8500#)tongue at 1000#.I believe some wieght left in the back of this truck would be a good thing however Im looking for answers.I've called a lot of places here in vegas and the all give me the tongue wieght for an answer.Im thinking 750# springs but what do I know.THX in advance.
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Old 07-22-2006, 07:05 PM   #2
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Quote:
Originally Posted by richnritab
I know this question has been asked a lot however its been a while.I read a resent post by andy at inland rv that states some people are adding to much spring to thier hitches.I can't remember where I saw it but it was a formula inwhich stated that a 3/4 ton truck would need 550# springs.Im not doing andys formula any justice and I do realize it matters how much tongue wieght you have.My question is this... Which springs do I need with a equal-izer brand, distribution hitch on a 06 GMC Sierra DuraMax crew cab pulling a 31' excella (loaded 8500#)tongue at 1000#.I believe some wieght left in the back of this truck would be a good thing however Im looking for answers.I've called a lot of places here in vegas and the all give me the tongue wieght for an answer.Im thinking 750# springs but what do I know.THX in advance.
I'd go with your hunch of 750lb springs. Your truck can handle more tongue weight than most, so a little undersprung seems just right.
i tow with a 1/2 ton, and my 1000lb bars are too much for the Overlander, it seems that my Dual Cam HP does only a marginal job of dealing with sway. I will try 500lb bars to see if it improves any.
However, you're not asking about the sway issues. So. I suggest going with the 750lb bars, since you do have a HD truck.
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Old 07-22-2006, 07:15 PM   #3
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Detailed Formula Available...

Nick Crowhurst did an engineering analyisis right here on these forums. You plug the values into his equation and voila, it spits out the spring bar value you need.

For my '76 Sovereign 31' behind my 2005 Chevy 2500HD Crewcab,the value was 620#. But my tongue weight is only 500# (1000# sounds like a lot).

You adjust your hitch so the front springs on the tow vehicle still compress a bit, even if only 1/2 in.

If you have dual cam sway control, you must also ensure that you have at least 1 to 2 inches of deflection in your spring bars, or you will have no sway control as Uwe has observed.

Hope this helps!

I will search for the Crowhurst thread and pass it to you in a subsequent post in this same thread.

Found it! http://www.airforums.com/forum...sis-19236.html
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Old 07-22-2006, 08:11 PM   #4
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The 1000 pound bars are a bit stiff for your rig but, I would try them out in the real world for a couple of trips to see if they are good enough before I would go to the trouble of buying new bars. If the bar defection is adquete when you load up the chains to make the TV to sink reasonably equally, the bars will likely work ok. You are not likely to notice the increased stiffness in the ride of the trailer on reasonable roads and the steering of the TV will likely not be effected and the sway control will be adequete. If you intend to do a lot of back road roaming, the trailer may take a little more abuse and the lighter bars may be worth it.
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Old 09-26-2006, 05:46 AM   #5
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Quote:
Originally Posted by richnritab
...I read a recent post by andy at inland rv that states some people are adding too much spring to their hitches…
Andy may have mentioned the sentiment in several threads, but it caught my attention when he went into some detail in the “Resuscitate A Smushed Airstream?” thread. While I am a little slow in following up my promise to myself to acquire lower weight spring bars for my Overlander & ¾ ton Suburban combo, I have finally done it, and thought some of the details are worth sharing.

Using Andy’s spring bar width guide, it was determined that my Overlander had 1000 pound spring bars. Since my Airstream’s tongue weight is listed at only 478 pounds, and I knew that the previous owner had had the Reese Dual Cam hitch installed at a dealership, I was surprised at the selection until I remembered that the PO’s first tow vehicle was a mid-sixties Oldsmobile. 1000 pound bars would have been necessary with that car’s soft suspension.

Andy mentioned seeing a bend in the installed, properly selected spring bars. It made sense considering what the bars are supposed to be doing even though I had never seen my 1000 pound bars visibly deflect while the Overlander was hitched to my Suburban.

Since new-style spring bars are $300/set, I turned to Ebay and bid & won an old-style set of 550 lb bars complete with cam followers for around $20 plus shipping. Apparently the seller did not read Andy’s guide because the bars I received were 750 lb bars. Bringing this to the seller’s attention, I requested my money back plus shipping costs to cover returning the bars. The seller agreed to refund my money, but told me to keep or throw out the 750 pound bars.

Okay. So after PayPal advised me of a credit, the seller received positive feedback. A little later in the day I renewed my Ebay search for 550 pound bars. To my surprise, there was the same seller with a set of non-dual cam, Reese 550 pound bars for sale. I couldn’t really get mad as I had asked for my money back instead of asking for the right bars. So after PMing the seller & asking for a width measurement, I bid on & won this set for a few bucks less than the 750 pound set. So now I have a total of three sets of each of the different weight spring bars.

The odd thing about both the 550 lb & 750 lb bars is that none of the four bars fit that snugly in their respective trunnions whereas my 1000 lb bars do. In one of the pictures below, you can see evidence of this in the form of a misshapen, soft steel retaining pin.

Something else I did not expect was that both “new” sets of spring steel already have a bend to them with the 550 lb bars being the worst. Since the bars appear to be symmetric, plans are to flip them over in their trunnions, and effectively bend them back during actual use.

Does anyone see a problem with that?

Thanks,
Tom
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Old 09-26-2006, 06:13 AM   #6
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I think I would use the trunions that are not worn and team them with the 750 bars and try to properly set up the hitch per Reese's instructions. Once you have established the proper settings and weight transfer that makes the rig set right, check for the amount of defection of the bars that takes place. Follow Reese's instructions. You may need to use an unusual setting of the ball tilt angle to account for the fact you have reversed the bent bars. Bent bars are not a good sign since it means the metal has exceeded its yield strength, which will reduce its fatique life. I do not know what the deformed bolt is you showed but I would replace it with at least a grade 5 bolt (three dits on the top) as soon as possible.
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Old 09-26-2006, 07:57 AM   #7
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Your First Question

Quote:
Originally Posted by richnritab
My question is this... Which springs do I need with a equal-izer brand, distribution hitch on a 06 GMC Sierra DuraMax crew cab pulling a 31' excella (loaded 8500#)tongue at 1000#.
The Equal-I-Zer weight distributing hitches come in only 4 versions, 600/6000 GTW, 1000/10,000. 1200/12,000, and 1400/14,000 pound capacity. By these listings, I am indicating 600 pounds tongue weight, 6000 pound trailer weight xxx/XXXX, etc. I was told by a sales represetative for the Equal-I-Zer hitch, that a 6000 pound trailer would be better suited to go with the next size bar system which in their product is 1000/10,000. F Y I
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