Finally got some local tire dealerships to talk with me due to mutual friends. When assured I had a brain and was not a lawyer, information flowed freely, the ones I talked to were familiar with Airstreams and their special needs.
INFLATION: It seems that on the vintage units tire pressure was recommended, such as 45 PSI for the 31 foot units. 8 ply 7.00-15 tires were used. Their max pressure was 65 PSI. The sidewalls had to be doing some flexing. Also Interstates highways and 65 and 70 mph speed limits have been with us since the early 60s. We all know that if you over inflate a tire the center will wear out and if you under inflate a tire the sholders will wear out. I don"t remember the "seasoned" airstream owners complaining about tire failures as we do.
I have tried to get BG Goodrich to sent me an inflation chart for the Commercial T/A twice, but I keep receiving inflation charts for Michelins.
The inflation charts list the following information for RVs: A LT225/75R16 inflated to 65 PSI will carry a load of 2335 lbs.. A Pressure of 60 PSI will carry a load of 2190 lbs.. This goes all the way down to 35 PSI and 1500
What is to be surmised from this information?
1. Michelin/Goodyear tires do not require max inflation to be reliable, You can run lower pressures as long as the pressures you run are on the chart AND ARE HIGH ENOUGH TO CARRY THE LOAD YOU HAVE ON THE TIRE. Michelin states by the information in their chart that you do not have to inflate their tires to max pressure to get them to survive the journey. This is reinforced by the older units recommending a less than max pressure for their 8 ply (Load Range D) LT tires that used to be standard on the vintage units. As long as you run the appropriate lower pressures on the E tire you will get the softer ride and because of the different construction methods/rubber compounds the tire should not come apart. I run 60 psi last year with no problems and with no noticable temperature rise. According to the CAT scale I have 1700 lbs max on each tire. I'm thinking of dropping to 55 psi.
2. If you have to run a tire at max (rock hard) pressure to stop failures reguardless of load on the tire, maybe its time to change tires.
All this being said both dealers, both local one Goodyear, one Michelin/Firestone-Bridgstone laughed when I brought up the ST tires.
Both try to steer trusted customers to the LT tires.
***Its ok to put the E rated tire on your trailer just NEVER PUT MORE THAN 65 PSI IN THEM. Find out how much weight is on each tire and inflate them accordingly.
In my case, 55 psi represents a 17% weight safety margin.