You get least rolling resistance if your tires compress about 15 percent at road contact. Tire pressure should be a function of rider's weight, plus any cargo typically carried, and should generally be 10 PSI or so higher in back than in front. There is no one-size-fits-all number.
On my 700Cx28s I typically run 90 PSI front and 100 back. That's about as high as I care to go.
Having said that, I do go with the rated maximum of 65 PSI on my mountain bike (26" x 1.95").
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069