I ran 18 x 9.5 + 12 on the front of mine, pretty aggressive fitment. All depends on if you want to run a stretched tyre and how much work you want to do to your guards. I ran heaps of stretch and rolled and pumped the guards about 20 - 30mm (achievable without cracking the paint). Cops didn't love it but half my problem is probably my P plates. On a B series also so could go touch more aggressive on an FG.