Much depends on riding style. If you help the bike over rocks and roots, you can get by with lower pressure. I routinely rode my rigid bike with around 30psi in the 2.1 inch tires, and at the time I weighed about 190. I've never had problems with pinch flats, but I'm a rather decorous rider. The bike that gets me to the mountains is the bike that must get me home. 30psi gives much better ride quality, and isn't too bad on pavement. It's a trade-off.