Thanks Vik, very informative.

At 5' 8" and 70+ kg I don't consider myself a big guy. I inflate my 700c Vittoria Rubino Pro tyres to 110-115 psi and I'm happy with the ride, especially charging down a mountain or fast cornering on a crit circuit. if I go under 100 psi the ride starts to feel sloppy. Some of the guys I race with will go as high as 140-150 psi (which is way over the manufacture's specs), it produces a rock hard tyre with a rock hard ride. They claim it makes them super fast?

What about MTB tyres?
Some riders will deflate to 40 or> psi when the terrain is rocky or lots of tree roots, when I try that I get pinch flats, so I stay just over 50 psi.

Is it a case of each to his own or try it and find out?