front =? rear =315/35/17s or 285/35/18s ??

Im going to lower my car with eibach pro kit(im wondering what else ill have to change after this and why)

and im looking for a new rear tire set up 315/35/17s or 285/35/18s

what would you suggest i get ?

last question ...what is the largest tire size i can go with in the front on stock oem wheels (17x8)?

thanks