how to check/set new class c tire pressures

If you have trouble checking and adding air with beauty discs in place, consider spending some more money and having long custom formed solid brass or steel valve stems installed on rear duals and front tires if needed. This will cost between $100 and $200 at a Truck Tire shop, but it makes the process much easier.There are two main products. These are available from Tire Man and Borg to fit your rig. Do not install cheap screw-on extenders to the rubber valve stems. They are unreliable and the vibration will cause the rubber stem parts to fracture and leak. Keeping tires inflated properly requires periodic checking of pressure. Leakage and deflation can cause tires to blow out or come apart and steel belts can damage underside tanks, wiring and propane lines or cause loss of control.
Why RV chassis makers don't install these on all new RV's is a mystery to us all.

http://www.ridgecrest.ca.us/~tire-man/valve_old.html

http://www.borgtiresupply.com/owner/duallyvalve.pdf