I do believe you have that backwards. Dual tires may rub together from too LITTLE air pressure, not too much pressure. The Explorer tire problem was finally found to be caused by running the Ford recommended tire pressure instead of the Firestone recommendations(still ligitating). This made the explorer ride soft and smooth, but allowed the tire to roll off the rim enough to lose air in extreme situations. Addresssing the original question- Tire mfgrs publish charts showing the minimum tire pressure for different load weights. This is the minimum pressure recommended and is not correct for everyone. Duals do not require the same pressure as single wheels so the charts are a good beginning point.

 

I agree the charts state the MAXIMUM load per pressure, not recommended load.

 

Gain some fuel economy, gain some stability, run the sidewall pressure that the tire is designed for.

The Ford problems came from running too low a pressure..

 

Here's a twist on the Ford Tire problem related to roll overs.

My daughter has a Ford V-10 Excursion.
While coming back from her brothers house while in a 45 mph speed zone, she applied her brakes for a stop light. She lost control of the vehicle for a moment until it stopped, hitting nothing. She had my grand children in their sents buckled in.

She called for a tow truck, and my son
arrived. The lower ball joint had sheared into two parts.

A ford dealer fixed the front end for a minimal fee.

Now if that happened on the highway at 70mph, were braking was needed, needles to say, I think that would have resulted in a roll over. I wonder how many other roll overs involved lost of steering once the tire whent or did the tire follow the ball joint.

Not related to air pressure but still related to the ford issue.

Dave