Going with bigger wheels

[hanoverphist]

If I was to use 235/45/17 and 235/45/20 they ride should be similar or would rim diameter make the 20s more harsh.

Stock tire was 17x7 with 215/55. The ride is nice and cushy. I'm now using 18x8.5 with 235/45 and 265/40 in the back. Its not bad at all, but not cushy either. If I was to go with 20s I'm thinking 245/35/20 would be my tire size on about a 9in wide rim.

How bad would that ride be?

the stock tire has a sidewall of over 4" and the 20" 35 series is like 3.24" tall. lots of difference, more road noise as well as less bouncy. youll feel pretty much everything you roll over on that tire. im running 215/45/17 and thats about as low as id go, the 45 series is about 3.8" sidewall on a 215. on a 235 you should still be over 4" but not by much i reckon.