When I replaced mine, I was told that there were only a few 245's that would fit our rim, and all of those were sorter in diameter than the 235's they came with.
I know a lot of people use wider tires with spacers, but if you tow heavy, be careful of sidewall flex and wide spacers cause they can do more harm than good.
In the end, I stayed with 235/80/17's but I may go to a 225/70/19. 5 or 245/70/19. 5 the next time around. Three grand or so, i expect. Ouch.
Juan