I happened to see that Michelin lists XZE tires in 12:00R22.5. How long has this been? Last I saw, you had to settle for 315-80x22.5, which lowered top speed on the GMC's.
I never knew they went away, they were available 4 years ago when I cut one on my tag axle in Idaho ,I went with Toyos
My bus came with 12R22.5 XZEs. Nothing wrong with them, except A) they crack a lot, and B) they're bloody expensive. My present Yokohama 104ZRs tramline less than the Michelins, don't crack, and are half the price.
John