Air pressure

Off-road air pressure must be balanced with risk of bending a rim. Sidewall stiffness of your tire, weight of your bike, gear plus rider must also be considered. Generally, the short term benefit of lowering air pressure is nullified by changing terrain, as sandy, muddy conditions won't last a long as rim damage on the trail. The answer is; learn to ride all riding conditions with sufficient air pressures, generally above 25psi.