Don't change the wheel diameters, it will affect the handling and the looks, it was designed for 18's and 19's. You can go with wider rims and wider tires and there is a pretty good selection available in 18-19. At Wheelfire enter chat and see if you can talk to Luis Alvarez, he recommended the wheels I have on, over one that I had picked and I couldn't be happier. take your time, google info on offset, width etc. I have seen several CF owners who have put extremely wide tires on stock rims. That is NOT a wise thing to do, use Tire Rack site, it will tell you what size tires are recommended for what size rims, etc. They are professionals.