I've run in the low 30s on my clinchers (rated to 40psi min, I think) and into the 20s on my tubulars. And I'm a big girl.

And I won't say it, but I've never (you know what) -- knock on wood!

One way I learned what pressure to run was start high. I used to always start aroudn 45psi for my pre-rides. As I would ride the course, I'd see if I was bouncing around (too high). If so, I'd let some air out until I liked the feel. Then I'd check the pressure with a guage (I've got a digital one). After doing that for a while, I've learned what I like.

Although, I still raced with too much air my first race this season. I put the wrong type of valve stem extenders on my new tubulars and I couldn't check the pressure. It's was the first race with lots of distractions and I didn't take enough air out. Was sliding around all over the place.