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Why do tow vehicles "sag" in the rear, under a load they were designed to accommodate

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Why do tow vehicles "sag" in the rear, under a load they were designed to accommodate

Old 08-28-2015, 08:45 AM
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Default Why do tow vehicles "sag" in the rear, under a load they were designed to accommodate

I just read a report on-line at : http://special-reports.pickuptrucks....winner-is.html This 2014 3500 dually test tested the Dodge, Ford, and GM product offerings. It was a very close result, and the result winner isn't of concern. What my post is really all about is that all of the tow vehicle had the same issue noted in the report. I posted this question to "Comments" of the article, though I'm thinking that I won't hear back from anybody from that post simply because of the age of the test, which was done in 2014. But if anybody has some technical comments and suggestions with regard to that article, rear "sag or squat", or front end lightness, I'd very much like to read them. Here is a copy of my post...

I have a question for all of the manufacturer's and people that posted comments on this test. I believe in the "Results" section of the report, the author made a comment about how each of these 3500 duals "squatted" in the rear under the 16,000 pound load. Why is that? If these are designed to tow 16,000 or more pounds, shouldn't the suspensions be able to handle the load, without squatting and raising the nose of the tow vehicle which causes some amount of loss of front end control? I ask this question because I have the same problem with my Avalanche 2500. The Avalanche 2500 is set up to tow 12,000 pounds, though I limit the weight to app. 9,000 pounds. I did that by adding a 15,000 lb. Curt Class hitch to the vehicle. I even added another leaf spring to the rear to add some lift, yet still when the trailer is on the Avalanche 2500, even with the Reese Height Distribution Hitch connected, it still sags a bit and the front end gets a little light and bouncy. Without the WD in place, it sags even more, and the front end gets a little lighter as well, So, as a rule, I tow with the WD system in place. The motor and tranny are well up to the task of towing the 9,000 lbs long distance, it doesn't complain at all and actually get very good mileage, well better than 2 of the vehicles in this test, though in fairness, they were towing 7,000 more lbs. than I typically tow. I'm wondering if a supplemental air bag system for the rear suspension would help in my application. If so, does anybody have any suggestions? I know an Avalanche 2500 is NOT a Dually 3500, but honestly, I wish that they wouldn't be so prone to the "rear squatting" issue.
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Old 08-28-2015, 09:01 AM
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Here's the thing, the majority of guys buying 3/4 and 1 ton trucks these days are not towing full time. That means the manufacturers are softening the ride as much as possible. If they made a truck stiff enough that you could put 16k on a trailer and see no squat, unloaded the truck would be so stiff, no one would buy it. Also, a lot of people don't know how to balance a load on a trailer. Good to hear you have a weight distribution hitch, I'm sure that helps.
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Old 08-28-2015, 09:37 AM
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Agree ^^^^^^

Plus , many people don't take the time to hook the trailer at the right angle/ height.

They just buy a tongue and ball and away we go.

Edit in: nor having weight distributed correctly on trailer....this can be tough.
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Old 08-28-2015, 09:37 AM
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I believe they are designed to be sitting level when loaded down, hence the reason when the trucks are unloaded the rear sits higher.

They sag/can sag when they have a lot of tongue weight/the load not distributed evenly like stated above.

Don't know what size boat youre towing, but maybe its time to look for a new set of shocks for the rear, especially if they have more than 50k miles on them and you tow with it a lot (which sounds like you do).
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Old 08-28-2015, 09:51 AM
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That's a really good question. I would agree that they soften the ride to accommodate for the Customers preference (majority).

To follow your question with a question, then why not just make airbags/helpers factory? It's really not that expensive to go buy the $500 kit and install yourself, they should just make that standard.

I might add, that they are designed to operate with a standard/or maximum tongue weight, I'm sure on a heavier load, the weight is not evenly distributed on the trailer. Especially if a trailer is used for multiple purposes (length limited to place or adjust the load).
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Old 08-28-2015, 09:55 AM
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Air bags take care of the "sag" and actually help smooth out the ride on our lousy roads.

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Old 08-28-2015, 10:07 AM
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I'm not a super anal person but one thing that drives me nuts is when trailer arent sitting level. I prefer a little more tounge weight then average but then again my truck is a 1 ton and can handle the weight.

My pontoon and trailer are a little over 3500 pounds and I run about 600 pounds of tounge weight. Makes the vehicle very stable when towing down the road and about the only negative is my friends in there half ton boats can tow my boat.(not really a negative).

This might be to much tounge weight but it pulls down the road nice


Last edited by turbom700; 08-28-2015 at 10:09 AM.
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Old 08-28-2015, 10:55 AM
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Dodge is actually offering a factory air bag system on its 3500 that is supposed to automatically level the truck when a load is put in the back or on a trailer.
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Old 08-28-2015, 11:00 AM
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I don't understand why self leveling air bags and damping adjustable shocks are not standard. The technology has been there for years and we are talking vehicles that cost a lot.

True they are set up soft unlike older trucks that rode like ,,,,,,,,,, well trucks unloaded.
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Old 08-28-2015, 11:06 AM
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to me it makes sense to make that standard equipement but, I am sure the manufacturers will hold out as long as possible due to adding costs at build time. I'm currently looking at getting supplemental airbags for my old 03 ram to fix the squat when trailering and give it a softer ride when empty.
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