Ohh,, sorry yaar, typographical mistake,,, I am referring 31/10.50/15,,,,, 17 was by mistake
31/10.50/15 is equal to 265/70/15 which should be perfect for your FJ.
It might surprise you that some of the Dakar front runners opt for 205/90/16s. Though more commonly used sizes are 245/80/16 or 235/85/16
So lean cant be bad. I on the other hand have chosen 245/75/16 for my Evo, this is equal in circumference to Evo's OEM size 265/70/16
15 inch rims would be better because your FJ is already quite tall so to keep the center of gravity low, go for 15 rather than 16s