When you run a trail you want to air down to the right pounds per square inch (psi) on your tires. The BFG KM2s will run down as much as 0 psi. I usually run between 12 and 18 psi. 12 if you are going through sand ans snow, 18 if you are on rocks, but its all personal preference. As you approach the trail, you want to air down. Instead of waiting around, you should get a set of valves that automatically air down your tires to the right psi. Check out these valves. The are available here:
