Originally Posted by Steve Ownby
I think you are under inflated at 100 psi on your steer axle. I also put Michelin XZA2 315's on my Signature. The problem is that Michelin de-rates the 315 size when mounted on 8.25" width wheels. They publish a specific inflation table just for this application. You can find it in the Michelin truck tire data book in their tools section. On my coach, carrying just under 14,000 lbs on the steer axle, I need 110-112 psi. Still better than 120.
Steve, I've got the XZA2 Energy 315s on my coach, and I weigh in at 7650 lbs on my heavy front side. I used the tables I saw on the Michelin page and other than they are good for 9 and 8.25 inch rims, it said nothing about the rating on specific wheel sizes - it simply called for 105 psi at 7660 lbs. Now I am a bit of a hammer-head, so I treat that as the minimum and run mine at 120 psi.
I'd still like to see what they rate them at on the 8.25 rim - where did you find your info?