uhhhh, the stock rims will only safely hold a 255.
on the front, 10 inch rims with a 285 is the widest I've seen, and the rear I've seen an 11.5" rim, but the widest tire so far is a 325. I hope to do a 345 on the rear with a 12" wheel, if I can win a lotto or something to pay for the wheels.