Q5 max tire aspect ratio.

Hello all,

Received my Q5 recently (offroad pkg) and immediately switched to factory 18" rims at dealership smallest available for Q5.

Based on reviews, I knew it was a rigid ride but thought that with the 18's I'd be able to soften it considerably; haven't hit the sweet spot yet; my back telleth me so...

What would happen if I changed to tires with a larger sidewall height (aspect ratio)? Factory installed are 60; can I go to 65, and, will it further soften the ride? If not, can I install 17" rims on the Q5 or would the Audi designer police come to snatch me in the middle of the night? (17's seem to have a much larger choice of A/T tires to choose from). I suppose width has to remain at 235?

I live in a country with less than ideal roads..

Cheers