We started out with a 2001 Adventurer and traded up to a 2003 Journey DL 36LD. Since going full time, we are now in a 2004 Itasca Horizon 40WD.
I also had a mental problem with the Michelin 235/80R22.5 XRV tires on the Journey. They seemed soft and squarely. From the Freightliner web site it seemed as though the DL 36LD should have had the 255's. When funds became available, I traded up for Michelin 255/80R22.5 XZE tires. They are for the short/long haul trucking industry and have extra deep tread and extra UV protection. The ride was only slightly firmer but the handling was very noticeably better. And the load margin was great. I seem to remember running 90 PSI all around. I recalibrated the Speedometer using my Pocket Tech from CAT.
Our Itasca came standard with 275/80R22.5 XZE tires and with the independent front suspension, it drives and handles like a good car. After checking the weights, I am running 100 PSI in the fronts and 85 PSI in the rears.
It is important to remember that the proper pressure for a tire is weight dependent and has a great deal to do with footprint and sidewall flexure. As long as the manufacturers guidelines for inflation are followed, any pressure up to the maximum listed for the tire is proper. Don't run low, the sidewall will overheat. Don't run high, the tread will ware prematurely. And keep your duals matched. One duel running low will transfer the load to the other duel and cause it to overheat.
Check the Michelin websites, there is a lot to tire technology and explanations are easy to find.
Have Fun!! Mark & Donalda 04 Horizon 40WD no TOW 90,900+ miles and counting
Triumph Bonneville & Susuki S40 on the back