Goodyear makes the wrangler/mud in a 37" x 15" x 12.5. Great tire with the 3 ply side wall for rocks etc.. (basically this is max), the only problem would be if you haven't lifted your bko, than it just won't fit under your truck. Also 37" is pushing it with cromemoly shafts on the 8.8 and d44 front with mm/hubs or warn hubs. blah blah blah. Going larger than 37" your tire will start to role when crawling, and in addition if you go larger you will want d60 upfront and 10.25 in the back so you will need D60's and 10.25 which normally need at least a 16" rim min. Hopefully I didn't read to much into this question or say to much. Have fun with what ever you do.