Same here @MB, spending most of my time, when permitted, up the high country, I am more focused on ground pressure than floating such as you might want with sand etc. The widest i have run is the Goodyear Wrangler MTR in 32 x 11 and that worked fine - unsure if i would notice the difference going to 12.5 though. I would struggle to fit the 12.5" under my factory flares as well, as the offset the vehicle came with was set up for the tiny 31 x 10.5R15 wheels. Now running 17" rims, I will be looking at a set of all terrains and swapping the alloys out to those and putting the muddies on the steelies. The muddy's are 285/70/17's from memory and track very nicely, however I suspect the 86T mass helps a bit.