Just a place to put some blurbs that I tend to end up repeating.
Tire pressures are always a compromise. Low pressures grip better on many surfaces, but risk getting “pinch flats”, and or spinning the tire and tube and tearing the valve stem on bikes without rim locks. And heading back to the pavement with under-inflated tires will cause early wear, bad mileage, and bad handling.
What you actually choose to use for pressure will depend on a number of things: tires, speed, terrain, need, wet vs dry. Good tires with stiff sidewalls will resist pinch flats (and can go to lower pressures) better than ones with flimsy carcasses (like kenda k270 and shinko 244). Higher speeds and rougher terrain make pinch flats more likely. If you’re stuck at the bottom of a ravine, or the weak link in a group of riders, then dropping pressure and risking flats makes more sense. And you’re likely to slow down a bit in wet conditions anyway, so again, you might run lower pressures.
One “obvious” sign of over inflated tires (and/oor too stiff a suspension) is that the front wheel tends to bounce off obstacles instead of deforming and/or sliding along them.
Numbers… I’ve measured as low as 8 psi at the end of some hard rides. Normally I’d have my tires between about 16 and 22 psi, and not bother adjusting them. Some people will adjust pressures at the start and end. I’m 190 pounds on a 320 pound DRZ, pressures would tend to go up/down for heavier/ligher combinations.
How things work videos