Quote Originally Posted by Lisa S.H. View Post

And SadieKate is right- when the sidewall says "max. psi 120" that means if you inflate higher than that you risk a blowout....it does NOT mean that 120 is the recommended pressure! One will get more tire/tube failures with EITHER too high a pressure or too low a pressure.
My 700x28 Pasela Panaracer Kevlar-lined tires say max. 120 psi, but I put them at between 90-100. I ride on incredibly sharp rocky gravel roads (even over cow fields on occasion!), and in 4,000 miles I've only had one flat- due to a triangular piece of glass that got imbedded in my tire.
There is no real consensus about this. The number on your sidewall was invented by a lawyer who wanted to be an engineer but couldn't pass calculus. It generally includes a significant safety factor so they don't get sued as often.

There are a lot of things that determine the point at which your tire will fail. I run my front tire at or a little above recommended pressure and my rear tire almost dead on and my last sidewall failure was in 1993.

I suspect that skill plays into it somehow. More experienced riders can generally float their bikes over bumps and tend to avoid things that will shred their tires. Or they just get sick of flats, spend the extra money and get really good tires.