I just picked up a 2012 G37x sedan. It is stock now and would like to put winter tire on the OEM wheels, then run 18's in the summer. So far the ones I like are the 18x8 Niche Targa offset 40. Can I run those with 255/45r18 tires? Would I have any clearance issues?

 

Those will be fine although a 245/45/18 is a better fit on an 8".