Fleet Man wrote:
I believe the 255/80R22.5 is a size designation used only by Michelin but I could be wrong. Many of us have replaced those with 265/75R22.5 tires made by other manufacturers since they are almost identical in revolutions per mile (541 rpm) and do not require a speedometer adjustment. Bridgestone, Toyo and others offer the 265 tires. Using other than Michelins does not seem to be a problem for most, I recently went with Bridgestone R250F's on ours and am quite satisfied.
Just a point of interest, my tire guru tells me that the Michelin sizes seem unique but it's because they measure their casings from the inside, while the other manufacturers measure from the outside. BTW I just replaced my Michelins with Sumitomos and so far they are great.