I found something on Michelins site that might help.
Go to http://www.michelintruck.com
Hover on products. A sub-menu will open. Hover on New Tires and you'll get another sub-menu. Click on new tires. Enter the info that best describes your application and click continue. Click on one of the resulting tires and on the page that opens, find the button that says Load and pressure. This will give you a chart showing the minimum air pressure at a given load.
Keep in mind, if you run "Drive" tires on your drive axle, instead of "steer/any position", they won't be listed under recreational vehicle. You'll need to look under "Truckload Carrier".
Having read the chart, it seems the minimum recomended air pressure for an 11R22.5, if you are running "drive tires" on your rear axle and the load is 17,520lbs or less, would be 70psi. 75psi. if the load is between 17,520 and 18,320 etc.
The pressure/load is different for metric tires. Also different for "steer/any position" tires.
Hope this helps.
My last statement wasn't intended as an attack. Sorry if I offended you. It was meerly a word of advice.