Corkey05 has it right. The shorter lighter coaches can do just fine on smaller wheels and tires. It wasn't too many years ago that all gas coaches were using 16" wheels. As they grew in size and weight they also got bigger wheels. Diesel coaches have always been considerably heavier and have used truck/bus sized wheels. The air pressure, required to carry the total loaded coach weight, has more effect on ride than wheel size. (hitting potholes excepted)
My old coach uses 16" wheels (the actual diameter of tire and wheel is only about 1-3/4" less than the 19.5" combo), so the ride is not much different.
The coach builder has to decide what length/weight coach he is going to put on a given chassis. It's part economy, and part matching the chassis to the coach, that determines the chassis configuration and required wheel size.
Personally, if I wanted a small coach I would certainly NOT rule out one with 19.5 wheels if that was all that was required to handle that weight. I might even prefer it for tire replacement cost considerations.
My point is, that 22.5" wheels (while maybe makes you feel more like one of the BIG Boys) does not guarantee a better ride. In fact, on a small coach, it may well be the opposite.
