It is on a data plate, typically located next to the driver's seat. It will list individual axle weight limits and maximum gross weight.
Using those weights you now need to look up the tire pressures for each axle.
http://www.michelintruck.com/micheli...ion-tables.jsp
My guess is you are seriously overweight and should start considering how to bring those weights down to something near the limits for your coach, or recognize that you may have to adjust your driving habits to compensate for the additional stresses those excess weights impose on your air bags, brakes, bearings, etc.