I had initially LR D 256-75-16 tires on a sw rig back in the early 90's when E rated ones were not out. They towed every bit as well or better than the stock 245-75-16 LR E rated tires. Both at 3000lbs of total rating. In my case, later went to E rated tires. Frankly, I was just as well off with the D rated tires, less money, took wife out to dinner......
I've seen issues as you describe more in larger MDT/HDT tire sizes. There seem to be no longevity issues etc with them. If LARGE trucks have this issue. I am sure small trucks will have the same very few issues.
I've personally found the squishy tire side wall is more from the actual tire brand and type than the psi in the tire. A steel sidewall tire is always loaded lbs on it straighter up and down than a polyester only sidewall tire of the same size and load rating.
The worst squishy tire I have had, was a set of Michelin XRV tires, ones for motor homes in an 8r19.5. Some got put on my mdt one time, they did not last but 48 hrs on it. Even with the truck empty at 12K lbs, the tires full loaded psi at 18K lbs, were non driveable with an empty truck vs other brands and even other michelin tires of the same size etc. They were made a bit soft for a softer ride for those with lighter chassis gvw mdt based MH's. not good for one using the same chassis as a dump truck. if we want to talk the XDE M+S on the rear of my truck.....great tires! XRV suck!
Marty
