We run 700x28 Continental 4 season tires and until recently have been running about 100psi. With the bike, we're about 315 pounds.
Silca has a
tire pressure calculator that I've been messing with and based on that, I lowered the pressure to 90. It's wants you to go even lower, but I'll try it in steps. 90 has been working out great so far. Bike handles great, it's a bit more comfortable over rough road sections, no pinch flats yet, and maybe we faster? Or maybe we've just had a few good days...