Here's a writeup I did looking at air tire pressure on my V6, 4-door '05 TRD 4x4 with 31" Goodyear silent armors. It's interesting to see where tire pressure reduction actually kicks in to be useful in sand. I've run at 17psi and still dig with these tires. They're great in snow but I've had to really put them down in sand. And, sometimes when I feel dumb, forget to put it into 4x4 just to practice digging.