My 1989 toyota pickup has 235/75/15's. They aren't that big but they do well on the trails I drive. Planning on going up to 30's or 31's. But my main question, does anyone run these tires and if so what's the PSI you have them at? and do you deflate them when you go mudding and if so to what? I believe mine should be at 40 PSI since the most pumped up tire is at 37 PSI and the least 33 PSI. But I'm thinking aboung running them at 35 PSI in the moutains or maybe 30 PSI.