Since my undergrad days (UCLA ca. 1970, when/where bicycle theft was rabidly rampant), I have always had one or more theft-resistant beater bikes I could lock up without worrying too much, and I have not let my better-looking, more-expensive bikes out of my sight. Over three decades, I have lost two bikes, both junkers, to theft.
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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