whats the biggest tire i can fit in a new explorer or mountaineer??

no lift i need to figure out what size tires will fit.
it's got 245/65/17 right now and i want all terrains well it's for my uncle who hates the POS bfg that are stock on it.

 

[Texplorer]

Well if its a 91-01 it will be a 31/10.50/15. But since you said its a stock 17" rim with BFG's Im guessing its an 02-up so I have no idea what the biggest size you can put on it. I know of 1 person who put 31's on an 02 but I dont know if he trimmed.

 

[chrisrbarrow]

Some one on this site by the name of captainkev put 265/75/16 on his 03 XLT
and said the tires only rub at ful turn on the inside plastic skirt and just did a little trimming. A 265/75-16 is 31.7 inches and a 265/70-17 is 31.8 inches if that helps!