Originally Posted by
jowilson
I haven't gone as low as 29 but I have gone to about 38 and, while looking at the tire while biking around, was scared to death to continue on at such a low PSI. I'm going MTBing this weekend and would like to settle a few things once and for all.
You can't sort it once and for all, because tire pressure should be set according to conditions. Pinch flats usually happen at higher speeds and in rockier conditions. Of course you'll want higher pressures then. At 120 lbs bodyweight,
maybe 35 to 40 psi. If you ever go on slower, more twisty or wet trails, you may want 20-25 to get any traction at all.
My advice: carry a spare tube, and learn how to change it. Practice a few times if it will settle your nerves. Trailside flat repair should not be a frightening proposition.