RE: My 1993 Mark VIII
What size tires are you running Max???
Chances are, my sidewall is very close in size. I have no ride complaints on 20s, but the roads are pretty good around here too.
With a 245mm section width, and a 40 series tire, the sidewall ends up being 3.8" (40 percent of 245mm). Even with a 245/45/18 up front, you're only gaining 1/2" in sidewall. I think you'd need to be running 275s all around AND 45 series tires to justify improved ride quality. That ends up being about and inch taller. IMHO, the front tire size is most important.
I'm gonna run a 35 series tire up front next time around to see what kind difference it makes.
Kale