help please on rim&tire setup

[dahawkster]

OK so Ive been searching for a couple of days now and cant find my exact answer and could use some serious guidance please..I currently got a free set of RX8 rims but they are 18x8 with 50 offset so I know I have to run a wheel spacer but can anybody tell me which one I should use and if I will have to run extended studs, and will I be able to run a 225/45/18 tire I pretty much only see people running 235/40/18 I wanna try and fit the tire with the bigger side wall for a better ride.THANKS

 

[Breezio69]

15mm spacer will poke you out a bit from the fender, 10mm will fit flush but you'll still rub with a 225... so 15 it is

 

[dahawkster]

So will I be better off just getting the 235/40/18? and will I have to roll my fenders?