285/75 is a VERY large size to put on stock 7" wide rims. I can say that I had 265/70r16's on mine without any trimming. 285's would be both wider AND taller & require a rather large amount of trimming, I'd wager. I currently have 265/60r18's, and I had to trim a bit on the front of both front fender wells. Based on that experience, I'm positive that 285/75 would require a HUGE trim. Plus, the speedo would probably be off by 10mph.