There's not much difference in the tires. LT235/75R15 outside diameter is 28.8 with section width of 9.1. The 31x11.5R15 shows an outside diameter of 30.5 with section width of 10.8. That's about 5/8 of an inch on each side. I would go out and measure the clearance now to have an idea of what will be needed.


Fred
52 3600
69 C-10