[Jimmy N.]

I have no idea what the Fiat engineers were thinking when they put coils springs in a cummins truck...

It was probably an effort to satisfy those who prefers a car-like ride.

Yeah like what has been said you need big leaf springs on the back to help with the weight.

It's not a matter of needing leaf springs. Most tractor trailers do very well with air springs, and large locomotives get around fine on coil springs. How those different suspension types are put to use is what matters.

Either way, a late model Ram 2500 isn't a good "foundation" for a camper, for a few reasons.

 

[Jimmy N.]

Then its a spring issue not a tire issue

Except that you really should look at a tire as a series of springs, as seen from the side. Especially when balancing one, which is why road force balancing works so well.

 

[Jimmy N.]

...but when you're 20+ miles out at sea and things start to go down hill you (and your craft) have to be able to handle it so you dont end up as an article in the news paper the next day.
-Ej-

Hey, as long as it's a downhill, couldn't you just coast to shore?