I strongly recommend using tires designed for 70 or perhaps 80 PSI on smooth-sided rims. The last time I checked, Harris Cyclery had some appropriate Continentals. I use Schwinn 27 x 1-3/8" knobbies on my UO-8; the sidewalls read 70 PSI, so I generally inflate them to 75 or so, never more than 80, and they have served me brilliantly.
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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