I was wondering what everyone thought was the best trail tire in sizes 31 to 32 for a 15in rim i am browsing around looking for tires right after i buy my roof rack and new axel so i want to know what to keep a eye out for on craigslist i was thinking about some good year mtr's but what do you all think??

I think 33s are perfect, honestly. Not too small, not too big.

I agree at least 33x12:50x15" on a 15x8" wheel with 3 3/4"'s of BS.

I have to agree 33" tires on a 15x8 is a great tire for a dual purpose DD/trail rig great selection , not too heavy , still streetable won't over stress parts and cost is decent.

I have 33's on my XJ with a small lift and some trimming its my dd. My dedicated trail rig has 35's. Once I do a axle swap up front on it I'll probably run 37-38" tires

That being said, keep in mind 33s are a tire you'll want to re-gear for. I've been running 33s on my stock drive train for about two years now and I'm going to finally make the jump to 4.56 this year.

You can get away on the stock drive train with those 31s if you want 31s.