CapriRacer,
Note that my comments on Load Range upgrading were that it was for reasons other than for load carrying and that I did not relate heavier duty tire performance as being because of tire stiffness. What I want in a tire for increased ruggedness is thicker material everywhere in the tire.
My reasons were all about heavier tire construction for better puncture resistance, better sidewall abrasion resistance, and less heat generation per mile due to reduced sidewall flexing -> all at any given pressure ... so "stiffness" is not the issue.
The truck camper owners talk often about using "HD" tires for added tire ruggedness. Perhaps someone could explain the difference between an HD tire and merely using a higher Load Range than required "regular" tire?
So far IMHO, I think the difference is (mainly) one of targetted marketing.