Tire size

Thank you, all. As it turns out, the Michelins that couldn't be found are due to being discontinued. It's frustrating, to say the least, when you're dealing with a tire shop and they don't know this basic information. I've managed to locate their replacements. Thanks again.

As rgatijnet1 says, there could be a slight difference in speedometer reading. I changed my tires from Michelin to Toyos, and now at 60mph on the speedo, I'm actually going 58mph (radar and also a friend driving beside me). Not a big deal.

Al

There are a few things that you really need to check when changing tire size. One is the diameter. Any change in diameter can affect your speedometer as well as your fuel mileage. If the two tires are within 1/4" it should be no problem.
The second thing is tire spacing between tires with duals. Different tires on different rims have a minimum distance that must be maintained between the tires when mounted. If the tires are too wide/fat, the distance between the set of duals may cause the tires to rub against each other.
A third thing is the load rating. You never want to go to a tire with a load rating below what the manufacturer recommends for your coach. If you go with a higher load rating it may result in a harsher ride.

As long as all tires on an axle are the same, no problem with different ones on different axles.

A 295/75R22.5 and a 275/80R22.5 are virtually the same size tire. Approximately a 1/4" difference in width and ride height. The 295/75 is a direct replacement for the 275/80. Go with the Continentals, they are just as good as the Michelins.

What size are the rears now?
Different size from front to rear will not make a difference.

Millions of miles on trucks, and rarely did steer tires match the drives.