Car Trailer Tires

An old-school tire-guy up-here told me the reason why many of these tires self-destruct is that they do not use natural-rubber like they used to.

I have a set of O L D nylon tires on one of my motorhomes that I am REdoing .... there is ZERO sidewall "damage" or cracking. The tires were put on in the late 70's or early 80's.