Rear end sag

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Aug 22, 2016 | 10:07 PM

#16

mecdac

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From: In the field...

Quote:

Originally Posted by pirate4x4_camo

Excursion has a rear spring rate of 420 lbs inch. therefore 500 lbs will compress the rear spring roughly 1.2 inches ..... mother in laws results may vary

@pirate4x4_camo
Will that "spring rate" of 420 lbs inch remain constant?

Has it deteriorated over the past 16 years?

Aug 22, 2016 | 10:35 PM

#17

WE3ZS

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Joined: Jul 2010

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From: Media PA

Quote:

Originally Posted by CharlyG

I haven't used any WD bars since I had a Suburban (a TON of sway). The 3/4 ton part seems to work just fine. The dry weight of the TT is 5125 lbs.

I seem to remember being told if the trailer and EXC(when I was told I had an F350) stay level after hooking up, I don't need WD. Of course that was 10 years ago and well, let's not go there!

You should be using a properly setup WD hitch system between an EX and a 6000lb+ TT.

Aug 22, 2016 | 10:42 PM

#18

pirate4x4_camo

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Joined: Apr 2011

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From: Northern California

Quote:

Originally Posted by mecdac

@pirate4x4_camo
Will that "spring rate" of 420 lbs inch remain constant?

Has it deteriorated over the past 16 years?

The excursion uses a "constant rate" leaf spring design so yes each inch you compress the spring requires 420 lbs.
1 = 420 , 2 inchs requires 840 lbs ect ect

The rear of the f250 on the other hand uses a "2 stage variable rate."
The first stage is the main leaf pack and has a constant rate through its travel of 320 lbs per inch, Then at the last 2 inches the "overload" spring comes into play at a rate 670 lbs per inch. This makes it "variable rate" Not to be confused with a progressive rate spring like used in coil springs.

Has it deteriorated is a great question.
The easy answer is no. It still takes the same force to compress the spring 1 inch, what cause the spring to sag is they loose temper. temper is what keeps the springs shape or arc. So the arc flattens out and the vehicle sags but the metal itself still requires the same force to make it deflect 1 inch.

Aug 22, 2016 | 11:03 PM

#19

CharlyG

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From: West Hills, Ca.

Not that it will change any minds, but we never travel with anything in the tanks. We only stay at full hook up places. I don't think we've ever had fresh water in it. I doubt if there's more than 5600 lbs in all....

I could see the difference when I had a Sub, but the 2 pickups(F350 DRW & C2500) never sagged enough to take away any steering control, and I had no sway going on. It's true I have only gone to places in Socal in these 10 years so about 2 or 3 hours away is all we get.

Aug 23, 2016 | 12:10 AM

#20

pirate4x4_camo

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From: Northern California

If you use the 420 spring rate to figure how much the rear will sag if you but a 500 payload in the back of the Ex remember you have 2 springs so the load is 250 each spring. So the ex would sag about .6"

Aug 23, 2016 | 08:49 AM

#21

CharlyG

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From: West Hills, Ca.

ok, I spent a little time thinking back thru the last 10 years and realized that I had lost the ball with the bend, and without thinking purchased a straight thru 3 ball. With the rake of the 98 Chevy C2500 LB, when I dropped the trailer on it straightened everything out and no WD was needed. Even though the straight thru 3 ball is perfect for the EX, when I drop the trailer it's gonna drop the back of the EX. I see that the best selling WD on Amazon is the EAZ-LIFT, but there is a Curt that will handle anything that I intend to put on it...

https://www.amazon.com/17007-Round-W...ribution+hitch

Any feedback?

Aug 23, 2016 | 09:19 AM

#22

jasoncw

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Joined: Jul 2007

Posts: 346

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From: Brownstown, MI

You get what you pay for. Honestly I would opt for a hitch with integrated sway control. Like the Blue Ox SwayPro, Equal-i-zer, or Reese Dual Cam. They are a bit more pricey, but worth the extra cost.

Aug 23, 2016 | 09:30 AM

#23

CharlyG

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From: West Hills, Ca.

I'm never gonna get a big TT. I just need one that sleeps 2 with a walkup on both sides of the bed....I won't know about sway until I take it out, but I had no sway with the 3/4 ton 2wd Chebby, or the F350 dually with no WD.