Whats the biggest tires you have put on the back on the stock rims.

 

245/45/16 is the next size up that will fit on stock rims. It's the biggest that will fit. I don't think there will be any fitment or rubbing in the front but I haven't tried.

I am personally satisfied with the stock size and rim. The bigger the width gets, the more the car tends to follow the groove on the street, especially with the hard suspension on my FD.

 

Im running
245/45 ZR 16 - rear and stock in the front
It runs fine but I am wishing that I had gotten the same front and rear for tire rotation purposes.