i run 30-40 psi in the rear! front dosnt really matter as long as its over 10psi!(barely touches the ground anyway!)
found if ya run lower then 30 in the rear, where i ride, ya get both pinch flats(rocky as all hell) and after that rim spin to tear out ya valve! so yeah thats why i run 30-40 psi!
(on my tyre it says to run it at 38psi i think)
if i was riding a different place with less sharpish rocks the size of your fist i'd definatly lower my pressure! but at the moment its all good!