i usually run mine around 10-12 on hard/soft loomy tracks, and if is kind of rocky i usually put 15, just cuz im cheap and i dont wanna burst the tire haha. But usually the less air pressure the better traction, this only applys until a cirtain pressure, if its to low, the tire will actually slide on the rim, which will cause lose of traction, if its to high, there wont be enough tire on the ground and will slide alot, giving less traction. thats just wat i kno, hope it helps.
-Tony #422