just about to buy some new tyres to put on my 18" S-Line 9-spoke alloys for my S4. previous size was 235/40 which I ran on my old S2, then the wife's A6. It was also the correct size for the A4 (B7) S-Line. looking at rolling circumference, the 225/40 x 18 is closer to the 225/45 x 17 - originals on the S4. also the 225's are a lot cheaper than 235's. and i fancy Conti Sport Contact 3's and can't seem to find them in 235's what should i go for ? any ideas?