I'm going to be putting 18x8.5 et 35 wheels on my 2008 a4 come spring. the tires wil be 215/40/18. Im going from 17x7.5 et 45 and 235/45/17. I am also going to be installing coilovers as well. With this set up is there any certain spacer size I would need, if at all. I know I need to remember since Im putting the coils on I might not clear the suspension. Im looking either to be flush or not much poke at all. I'm new at this so any info would really be a great help.

 

A wheel that wide with a 35 offset is at risk of rubbing the suspension. I have 19x8 wheels and 235-35-19 tires and I'm lowered 2.5". I'm running a 37 offset and on compression of the suspension my outer tires rub the fenders. You're running narrower tires and stretching them, so you may have more wiggle room on tge fender issue but I'm thinking that with the width of those wheels, you're going to have either fender rub or suspension interference depending on whether you run spacers or not (which would probably be only about 5mm spacers).