Reference to car tires and recommended pressures is a good one, but of course the manfacturers have a much better idea of what the "vehicle" weighs than they we do for bikes. And rather than provide just one recommended pressure, some cars specify a range of pressures based on load and speed. EG, the New Beetle turbo had a set of pressures on the placard for full/light loads on the and under/over 100 mph speeds. The rear pressures varied quite a bit with light to full load, ie, from 28 to 38 psi.
For bikes, I've seen a chart of weight vs recommend pressure vs tire width, maybe from Conti? IIRC, on 23mm tires, the 120 psi max is recommended for riders over 180 lbs. My GP4000s box says 110 psi is the recommended pressure for 23mm. I've read that 25 mm tires will have lower rolling resistance for riders over 180 lbs, even while running 10-20 psi less, but have never tried them personally. I'm 190 lbs currently, and run 100 psi front, 110 rear. I like the increased grip and "roadholding" feel on fast descents that the reduced pressure gives, as well as the reduction in cuts/punctures.
For bikes, I've seen a chart of weight vs recommend pressure vs tire width, maybe from Conti? IIRC, on 23mm tires, the 120 psi max is recommended for riders over 180 lbs. My GP4000s box says 110 psi is the recommended pressure for 23mm. I've read that 25 mm tires will have lower rolling resistance for riders over 180 lbs, even while running 10-20 psi less, but have never tried them personally. I'm 190 lbs currently, and run 100 psi front, 110 rear. I like the increased grip and "roadholding" feel on fast descents that the reduced pressure gives, as well as the reduction in cuts/punctures.