Goodyear Endurance Radials

[Tireman9]

IMO Starting with tires that by their initial design intent were allowed to be rated to carry more load than same "size" tires but with the original 65 mph speed limit we end up with ST type tires.

It is the air pressure that supports the load. Else why are there Load Inflation tables in TRA, ETRTO, and JATMA?

The basic form of the Load Formula is Load = Air Pressure x Air Volume with some minor adjustment for type of service (car or truck or trailers that were not allowed to carry passengers) I have never seen or heard of a table that provides Load vs Construction features.

The use of cap ply material is normally the "go-to" when a tire engineer wants to improve the high-speed performance of a tire. I know this is what I did a number of times back in the early '80s when speed ratings became common for the US made tires.

We need to remember that ST tires became speed rated in a response to FTC anti-dumping regulations that "excluded" tires with Speed Ratings. If I, as a tire design engineer had been given the task of developing "new" ST tires that could carry a speed rating (something better than 65 mph) One of the first things I would have tried would be cap ply/strip.

The idea that the RV trailer company would select the smallest (lowest cost?) tire that would meed the MINIMUM DOT requirements is a concept that has been offered a number of times. While there have been a few RV sold with some reserve load I am sorry to observe that they were in the minority.

In an effort to help RV owners I have tried to offer methods and guidance to help owners to select tires that would not just meet the DOT minimums but to many times exceed the DOT requirements.