I have seen a few mazda 3's with the RX-8 wheel package and havent heard much on rubbing in the wheelwells unless you got a nice mad drop on your ride. With out a drop you will be fine, but will have a ugly gap. If your looking at tire sizes, 225/45/R18 is not a bad set up. you will not rub. trust me i have 225/45/ZR18 on my mazda 3 HB and its dropped. Lower then i want, but i have no rubbing.