Back in the 90s when we were racing the common thought was that the narrowest, fastest tire, pumped as hard as possible was the optimal setup. The harder tire pressure didn't stop us getting pinch flats, as was hoped, and it certainly made for a jarring ride! Research has now shown that the narrow hard tire is actually slower than a wider softer setup. And indeed that today's common 90psi pressure may be the slowest setup of all.
Listening to this podcast made me re-assess my tire pressure. I remember the real aha moment was when they discussed experimenting with tire pressure on the cobbles and the bike was faster the lower the tire pressure, until they broke the rim on the cobbles. Since then it has been a journey of exploration and experimentation.