My truck came with 4 BFG AT's 2 of them are 31's I know that for sure cause thats what it says. I have a problem with the other too though. They are both have about 15-20% left and they are still taller than the 31's. The tires say they are 10r15lt 1040 m/s and I tried google but didnt come up with anything. So what size are these tires.