20in reps with 255/50's! Gives you plenty of sidewall and a real nice ride. They are also taller than 275/45 by a margin.. I got nitto 420's on mine and live in the boonies. I wouldn't go anything further than that though. I'm sure you can get a decent 255/50, but remember its a 20in rim so tire choice will be alot more scarce than a 18inch.