Rear-end sag while towing

[mistersmallz]

I have 2019 ford expedition platinum with the max tow package. It’s rated to tow 9200lbs max/ 920lb tongue weight and has a payload capacity just over 1500lbs. I use it to tow a 34ft Keystone Bullet 290BHS travel trailer. It’s 6000lbs dry and 7000-7500lbs loaded with loaded tongue weight of about 850lbs. I’m using an Equilizer 4 point stabilizing WDH that’s rated for 14,000lbs max/ 1400lbs tongue weight. I originally had the same hitch rated for 10,000lb max/ 1,000lb tongue weight. The issue I was having was too much rear end sag with the expedition having independent rear suspension so I upgraded to a heavier duty hitch to resolve the issue. It did raise the rear end closer to the unloaded level but now I have a lot of “bounce” and “porpoising” while driving over bumps. Would sumo springs help with this?

 

[Fasttimes]

You need to get to a scale with your trailer/truck set up for trip and really get the true numbers. 3-pass method at the scale, figure out if you are getting enough weight back on the front axle and if you have too much on the rear. My guess is you are too light in the front.

Also, you would be surprised how much more in on that tongue when hooked up for a trip with the propane and front storage areas loaded up. That is a big trailer. You are definitely at the tail end of the limits. If the loaded tongue is exceeding your limits consider moving weight around to reduce.

Sumo's help to get that last bit of leveling out and do reduce bounce a bit, but they don't transfer weight. I had them on my last Expy and liked them. I also tightened up the Expy with Helwig front and rear sway bar upgrades.

Get your WDH dialed in perfectly with trips to the scale, reduce and move weight around in trailer if need be to assist the tongue weight. Max air up the tires on Expy for trips.

All these things combined will help tremendously. But again, the thing that helped me the most when I was having issues with sag, sway and bouncing was getting to the scales and really learning what I had going on and tweaking the WDH. It took me a year to finally get dialed in how I wanted it.

 

[duneslider]

I did notice that adding the hellwig rear sway bar helped a bit with the bouncing on mine. Not exactly sure why it does but it does seem to help a bit.

 

[Grrumpy]

We tow a 7000 lb Jayco with right at 725 lb tongue weight. Just came from towing with a 2021 Ranger which, while adequate was not perfect. But, it did have the leaf springs which were easily modified with some suspension add-ons which helped.
Have been towing for more years than I care to admit, but our Expy is the first with an independent rear suspension. Not too much in the way of sag with our set up, but I believe the only way to "beef" up the rear is with a set of heavier rear springs/shock set up. Sway bars do nothing to cure sag that much, other than to give better handling.
On the Ranger I added a set of Bilstein's and a Roadmaster Active Suspension set up which added a great deal of stability and cured sag....unfortunately, its not compatible with rear coils/independent rear.
Being new to the Expy I don't know whats "out there" as to better/heavier capacity rear springs/shocks, but it may be worth looking into. Also, you may want to look into a set of E range/rated tires that can carry a much heavier load than the OE lower range tires.

 

[JasonH]

Get your WDH dialed in perfectly with trips to the scale, reduce and move weight around in trailer if need be to assist the tongue weight. Max air up the tires on Expy for trips.

All these things combined will help tremendously. But again, the thing that helped me the most when I was having issues with sag, sway and bouncing was getting to the scales and really learning what I had going on and tweaking the WDH. It took me a year to finally get dialed in how I wanted it.

This is the correct answer. Get a scale ticket and make sure that loads are distributed properly. Until you do this, everything else is a band aid.

The manual calls for 50% front axle weight restoration. So if the front rises by 1" when you put a load on the tongue, that should be down to 1/2" when you hook up the WDH. But that won't ensure you have the correct tongue load, so a scale ticket is still recommended.

I will say that Load E tires improved the stability while towing. Even with 51 PSI, my XL tires were bouncy and jiggled. With E tires and 65 PSI, the rear was rock solid. The E tires are probably overkill since D load will go up to 65 psi and I only needed 58 for my load. But at the time I wanted the extra puncture resistance. Knowing what I know now I would probably go with D and save some unsprung mass.