On the stock 15" rim running the stock p235/75r/15's on my '98 XLT 4x with the Trailer Tow package, the largest tire that will fit with no lift, suspension mods, or fender trimming is a 31x10.5x15. That is IF you can find someone to mount them. I have tried all the national tire shops (Pep Boys, NTB, Discount, Big-O, Goodyear...even Sams and Costco) in my area (DFW metroplex) and none with mount the 31's on my '98. Rollover issue and all that. I think I'll have to find an independent that will mount them and then buy them mail order.