I recently installed six new Michelin XPS Ribs on my Ram 3500. Initially I was somewhat disappointed with the stiff and rough ride but after some experimentation, found that if I run them 10 psi softer than the original Goodyears, 50 psi front and 45 psi rear, I get full tread patch contact with the road surface across the tire's full width and a much smoother ride. I guess the tires are so stiff the tread surface doesn't flex. I just returned from a 9400 mile journey pulling my TT and experienced no carcass heating, adverse wear, or other problems running the Michelins softer.
I also realized something about the OEM Goodyears a while back when a fellow poster, maybe RustyJC, commented that his OEM Goodyears were nail magnets. Mine were also. I've never had so many nail punctures as I did with the OEM GYs on my Ram.
As for the Goodyear Marathons, I wouldn't use them on anything heavier and capable of running faster than my lawn tractor. I've heard nothing but bad news from Marathon owners. Hundreds of owners, possibly thousands, have experienced blow outs and trailer damage with them. They were OEM on an Airstream I formerly owned. I never had a blowout but I experienced premature sidewall cracking and rapid wear. Tires with identical carcass and tread pattern but branded "Nankang" can be bought at discount tire stores and cargo trailer suppliers. I wonder if Nankang actually molds the GY Marathons for GY? They don't offer the size I use on my lawn tractor so I won't be buying any.
Harvey