You can run 275/55-17s which are a good moderate size. You can even get good snow tires in this size. I bought a set of '00 ML430 wheels for $400 shipped for snows. Better stance and proportions than stock 255/65s. 18s are better yet with 285/50s. Harshness is not increased with any of these, to my butt.
My 1998 w/ 285/50-18 Yokohama AVS/STs on Lorinser RS-3s:
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