Terrain has a lot to do with what tire pressure your running. If your riding on rough and rocky terrain with low pressure your not going to smack a rock and bounce off or up it. Your going to hit the rock and feel it hit your rim and dent it or puncture your tire, and you will also have a better chance of pinching your tires between to rocks.
Look at the sidewall of your tires to see what the recommended tire pressure is. Some people run there tire pressure lower then the tire likes to be ran at because the dumb sticker on the fender. The recommended tire pressure on the sticker is meant for a stock blaster with stock tires.