The very first time I took my Sube to the dunes I tried to not air down at all and see how far I could go. My car was really straining to get around and it was totally gutless. I then aired my tires down to 15lbs, and it helped out BIG TIME because the car just floated on top and never spun a tire. On my last trip to the dunes I got this thing totally stuck, and there was no one for miles to help. As a last ditch effort I aired all the way down to 9lbs. My car came right out of the hole it was in, and went EVERYWHERE the rest of the weekend. Keep in mind that these tires are 31x10.50x15's, but I am going to use it at that pressure from now on!!