Let set some baseline numbers to start with.....
The 22kGVWR / 26k GCWRchassis has a 8k front end and 15k rear, giving some F/R wiggle room to stay within the 22k GVWR.
The 24k/30k, is a totally different chassis than the 22k/26k. It has a 9k front end and 15.5k rated springs on a 17.5k rated rear axle. The 24k chassis itself has an UVW of ~500#s more than the same wheelbase 22k, so it nets you about 1,500# more carry capacity.
I’ll also note, that the 26k/30k chassis only differs from the 24k in the rear springs which are rated 17.5k and ride on the exact same 17.5k rated rear end; the UVW for the 26k is something like 11 (yes, eleven) pounds more that of the same wheelbase 24k, so you do net ~2,000#s more carry capacity but that is all over the rear axle (and if you tow between 4K and 5k, you’ll need to eat into that to stay within both the GVWR and GCWR.
All that out of the way, and back to the OP.
All else being equal, I think it is safe to say that a stiffer sprung chassis is going to have some additional harshness than a lighter sprung one. However, no one runs these things empty, and to a great degree folks (including us) tend to suff them until you can’t suff them anymore. The question then becomes how much do you stuff and at what point do you have weight problems, but I think the reality is that more spring = more stuff which all equals out with regards to ride quality related to the springs.
My fully loaded for “extended travel” (including full fresh water) 31SA on the 24k chassis weighs 8,400 on the 9k front and 14,200 on the 15.5k rear (I am also well balanced L/R). Given the specs above, and taking out the 500#s extra UVW, I’d be just over weight on a 22k and have to shed even more weight to pull my 4500# Cherokee. Given our actual weight, I have not gotten into a “why is this on the coach?” discussion, because I don’t want to get into that if I don’t really need to
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We also have factory Sumos, and I have no idea how they affect ride / handling, since this is our first coach, but I’ve never felt the need to mess with the sway bars or add a rear track bar to improve stability.
We’ve had our coach for 4 years now, and 32,000 miles. At 5,000 miles I had a Safe T Steer added as I thought it would primarily help wife with her tendency to “see saw” / overcompensate her steering. Once we got it trued up properly I would say it was worthwhile and there is the theory they help with controlling a front tire blow out.
At 24,000 miles last spring, I had the aftermarket Bilsteins put on after a lot of conversations with vendors at the FMCA rally in Perry last March; if nothing else, they certainly couldn’t hurt and the factory “Ford spec” Bilsteins were probably 1/2 way though thier life anyway; I do think they are are a reasonable but marginal improvement, but make no mistake, a bad bridge expansion joint is still a jolt.
Overall, we are happy with what we have, and greatly enjoy our travels.
Regards