Hi everyone. I am new here and am looking for some advice. I have a B7 A4 Avant S-Line Quattro Special Edition with RS4 style 18" alloys size 235/40 R18. I am looking to get a used set of wheels and winter tyres but do not know which size wheels will fit? Was thinking of some 17" wheels maybe off ebay but cant be sure if they will fit. Do you know where i can get some guidance? i believe offsets etc are important? Any help would be greatly appreciated as i am currently sliding around all over the show on some useless summer tyres!