Bill,
I have worked with one of the lead Michelin reliability engineers due to several inner dual blowouts that I had well within the useful life of an XRV model tire that was kept up with proper inflation. The fact is inner dual position tires have more failures then any other tire position and Michelin has not fully figured out that one yet.
His input to me was that the XZA2 Energy tire has one of the lowest failure rate of any tire that they make. It is a good choice. That 7 years is a real expectation from the date of manufacture given that the tires sidewall strength reduces with age (not miles so much) due to material degrade and it is predictable. Driving and getting the tires hot does help migrate the compounds that help protect the tire. The tire ageing starts from the date of manufacture and he indicated that there is no control in the field of storage environments. Temperature, humidity, ozone levels (which is a major aging factor) are up to Les Schwab and the rest to control and there is little to no controls in the field. Michelin sold off or farmed out its warehouse facilities several years back and he for one was not a fan of that. If there is welding for instance going on near tire storage that is a real issue as it generates ozone. I asked about side wall dressings and he said he would not use one, just soap and water. I asked about covering tires to reduce sunlight and he said that is not a big factor in aging within the 7 year useful life with the newer compounds but it does not hurt anything.
The net of all this is buy the best tire you can to handle the load, buy the newest dates, keep them inflated, drive them to highway speed at least once every month or two, stick to the 7 year expected life for replacement, make sure no welding is being done as a routine in the facility where you store your RV. If you find you have to add air to one tire position more than others, something is wrong and you need to get that fixed. If you add air, demoisturized air is better, you do not want the inside of a tire with steel wires in the sidewall saturated with moisture. The high pressure inside the tire causes slow air and moisture migration out through the sidewall. Under certain conditions the moisture can condense on the steel and cause rust which will roughen/pit the steel and can cause the sidewall cable to saw itself. This is a condition that is an issue only if a vehicle sits a lot like an RV.
That is about all that we as owners can do in defense of not having a tire failure.
Later Ed
