ntsqd said:
I still don't understand needing air bags on a 3/4t truck. We have one such, no air bags, and the O/L's are deliberately very late in coming into play. No issues, no exaggerated sway, truck sits level with the camper in the bed. As far as I know they are OEM rear springs.
Interesting comment regarding your O/L springs. I wonder if they are after-market?
I'm on my 4th Super Duty and all have squat some under a heavy load, camper, gravel, etc.. And all have had the enhanced payload (O/L spring) option or the OME suspension upgrade with overload spring installed. And as springs age, with a camper in the bed full time, the springs will eventually take a set to that weight and sag even when the camper is removed. With my Hawk wet and fully loaded, my overload springs (and I have the heavy payload option on my F-350) will just touch the spring's frame mounted rubber bump pads, front and rear. The air bags simply allow me to return the spring tension to the unladen position which is the most comfortable ride.
I've emailed/discussed spring pack ideas with Dan at Carli Suspensions quite a bit. It has been an education. Sadly Carli does not offer spring packs designed for heavy laden trucks 24/7/365. But there are vendors who CAD spring packs based on a payload figure. If your payload varies substantially (camper in bed a limited amount of time), then you will have to seek a compromise solution with a custom spring pack.
I opted for the 4x4 package (not FX4) so I could install the Helwig sway bars F/R and a few other more robust after-market accessories compared to the FX4 offerings. Sway without the rear bar was very noticeable. After installing the Helwig, no sway, at all.
My Wells Cargo trailer is a tandem wheel 7000# GVWR trailer. While I don't push trailer GVWR, a total weight of 4000# loaded for a trip would not be an unrealistic guess. When loaded with my BMW R1200GS and KTM 350 (BMW in more forward chock) the tongue weight is 440#.
Must I use air bags? No, but I much prefer the truck riding level at all times, so, I use air bags.