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Old 07-08-2014, 09:06 AM   #1
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Stiffer suspension?

I tow with a 2005 Yukon XL, with the 8.1 ltr engine. Tow rating is 12,000 lbs, plenty for my "new" 34' Airstream with slide out. But the 1,250 lbs hitch weight seems to be a challenge. The rear end of the Yukon sags or squats visibly. The Hensley hitch can't seem to throw enough weight onto the front of the Yukon. The rig handles fine, although the steering seems a bit "light".

I'm considering somehow beefing up the rear suspension, or adding air bags. I have NO experience with this type of thing.

Any advice would be appreciated.

Thanks
L.A. Phil (In Irvine)
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Old 07-14-2014, 02:03 PM   #2
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Airlift 1000 bags are fairly inexpensive and easy to install. GMC Yukon 2000-2014 Air Helper Springs - Air Lift 1000 #60769 - 2011 2010 2009 | SuspensionConnection.com

They will help with sag.

Also, Rancho RS5000 or the Bilstein 5100 rear shocks. You'll want a heavy duty shock, not the factory stuff, which is usually a little softer for ride comfort. If you're running factory shocks, there is part of your problem.

Hope this helps.
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Old 07-14-2014, 02:43 PM   #3
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Check with Hensley. Sounds like you need heavier spring bars for your hitch.

Tim
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Old 07-14-2014, 02:47 PM   #4
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Tim: Thanks. I already did that, after I discovered that they had sent the 800 lb. bars. When I told him what my hitch weight was, he quickly sent out the replacement bars (1,400 lb.)

Still won't handle it...

Phil
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Old 07-14-2014, 04:14 PM   #5
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Quote:
Originally Posted by pjtaia View Post
I tow with a 2005 Yukon XL, with the 8.1 ltr engine. Tow rating is 12,000 lbs, plenty for my "new" 34' Airstream with slide out. But the 1,250 lbs hitch weight seems to be a challenge. The rear end of the Yukon sags or squats visibly. ...
I'm considering somehow beefing up the rear suspension, or adding air bags. I have NO experience with this type of thing.
Adding Airbags does NOTHING for the axle rating. Best to take your rig as it is now and get a full set of scale readings. Get the unloaded axle weights of the Yukon, the weights of the three axles on the AS, and the actual tongue weight (don't forget to throw in the weight of the Hensley somewhere).

Usually the first thing to bust specs is the rear axle. With the extra weight of the slide on the AS, I'm betting that you are overweight with just the AS and Hensley on the tongue. I would not take a chance on overloading the Yukon.
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Old 07-14-2014, 06:17 PM   #6
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Quote:
Originally Posted by 87MH View Post
Adding Airbags does NOTHING for the axle rating. Best to take your rig as it is now and get a full set of scale readings.
No one said anything about axle ratings or airbags increasing them. He said he has sag/squat. Airbags can help with that. Especially on rear coil spring vehicles, GM uses a progressive and linear rate spring. The Linear rate springs will collapse or sag more under load than the progressive rate springs they use on the Z71's for example. Both have similar ratings, but both compress differently, and both ride differently.

Axle ratings is a whole other subject. If your sagging and NOT overweight on your axle, then Airbags are viable.
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Old 07-14-2014, 07:46 PM   #7
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I am certainly not an expert on tow vehicle suspensions but, I know from experience when I put air in the rear air bags in my MH I can raise the rear of the vehicle at least 3" measured at the wheel well. I would venture to say that adding air bags would fix your problem. The beauty of the air bags is when you are not carrying the load you can reduce the air pressure in the air bags and enjoy the smooth ride you had before. I purchased mine through SD Truck Springs and they were very reasonably priced.
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Old 07-15-2014, 08:08 PM   #8
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You can still have sag and not be overloaded. It's a problem in Dodge Ram 1500's for example.

To be 100% clear, all springs will sag, the difference is if they are a linear spring rate - put on x weight, get k*x sag.

The Z71 springs are non-linear (Progressive rate), so they get stiffer as you add more weight.

So for example purposes, put on 100lbs of weight and it might sag 1", put on 200 lbs of weight and it might sag 1.5" - whereas a linear spring would sag 2" with 200 lbs of weight.

So while a weight distributing hitch might help, it is not the end all be all of this sag discussion.

What your spring rates are, and whether they are progressive or linear is a factor in how they compress.

But hey, engineering and math, what do I know.
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Old 07-15-2014, 09:29 PM   #9
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12,000 LBS tow rating????

Quote:
Originally Posted by pjtaia View Post
I tow with a 2005 Yukon XL, with the 8.1 ltr engine. Tow rating is 12,000 lbs, plenty for my "new" 34' Airstream with slide out. But the 1,250 lbs hitch weight seems to be a challenge. The rear end of the Yukon sags or squats visibly. The Hensley hitch can't seem to throw enough weight onto the front of the Yukon. The rig handles fine, although the steering seems a bit "light".

I'm considering somehow beefing up the rear suspension, or adding air bags. I have NO experience with this type of thing.

Any advice would be appreciated.

Thanks
L.A. Phil (In Irvine)
L.A. Phil,

This enqueuing mind wants to know:

Where does your 12,000 LBS tow rating come from?

Everything I have looked at lists the following for your vehicle:

MAXIMUM TOWING CAPACITY** 8400 LBS

** When adequately equipped, which may require engine and/or other drivetrain upgrades.

And what is worse, the Maximum Gross Combined Vehicle Weight Rating (GCWR) for your vehicle is 14,000 lbs.

The Gross Vehicle Weight Rating(GVWR) for your vehicle is 8,600 lbs.

8,600 + 12,000 = 20,600 LBS which means you are 6,600 LBS overweight for your GCVWR, to say nothing of how overloaded your rear axle is; not surprising that it sags.

This tells me that your vehicle is beyond being inadequate for towing your Airstream.

Jim
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Old 07-15-2014, 09:47 PM   #10
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I think he's got the 2500, not the 1500?
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Old 07-15-2014, 09:54 PM   #11
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Maybe the first thing is to actually weigh the trailer at the coupler to see what the truck receiver is carrying, if that has not been done. Verify the Hensley has been installed with the correct angle on the head so the bars can get enough lift.
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Old 07-15-2014, 10:10 PM   #12
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No difference in the numbers....

Quote:
Originally Posted by dkottum View Post
I think he's got the 2500, not the 1500?
OK

I'll take the bait.

I looked up a 2500 and the specifications are identical to that of the 1500.

I'll now wait for the OP to respond...

Thanks,

Jim
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Old 07-15-2014, 10:29 PM   #13
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I found this chart showing his 12,000 lb tow rating statement.

GMC Yukon XL Compare - Engines and Performance - MSN Autos
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Old 07-16-2014, 03:23 PM   #14
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The 12,000 lb. rating is from the factory specs with the towing package, the 8.1 ltr engine, etc. Also verified in trailer Life's Tow Rating Guides.

http://www.trailerlife.com/wp-conten...Guide-2005.pdf

GCWR is 19,000 lb.

I will be weighing the rig on Friday. I would love to have an expert check out the Hensley to verify that it is installed correctly - anyone know of a Hensley Expert in So Cal?

Thanks, everyone for all your help!

Phil
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