Dumb question

I found a set of 18in sport wheels on marketplace and talked the guy down to $150 for the set of 4, I have a g37x and from what I can tell they are 18 x 7.5 up front and 18 x 8.5 in the rear. Can I run a 235/45/18 all around and not worry about the AWD lights coming on? I have 19x9.5 square set of tandems im running now and want to go to an 18