i cant seem to find a solid answer on the interwebs so here goes... Right... tyres on the A3, standard is 225/45/17 correct? now as far as i understand with the naked eye 245 is a wider tyre. the wheel size would be 245/40/17 which would be overall slightly smaller but mostly the same. Now am i right in thinking a 245 has more grip over a 225, obviously of the same tyre? So if the answer to the above question is YES, how does the SIDEWALL affect grip in a straight line? or while cornering? or is the sidewall still big enough at /40/ to not make a difference? Ok second set of questions. Why doesn't everyone have the widest tyre they can fit for better grip and just general safety? (what do the high powered S3's run?) Quattro Haldex and the use of a different sized tyre on the rear. Would this mess things up when the quattro kicks in and even show a decrease in grip? or would it not make a difference. And finally. Im guessing i can easily fit 245/40/17 on the rear with no rubbing problems, but what about the front, should i leave them as 225 in a perfect world, or would the same size also fit the fronts? And how can i tell if the 17" rim would support the 245? I apologise for the mass of questions, but its something that really has baffled me. Thanks alot. JJ.