I have used toeclips since 1968 and have no plans or desire to change. I keep them just loose enough to enable me to jerk either foot straight back and out when desired or needed.
What really impacts my power output is seat height / leg extension. I got on the Bianchi on Sunday morning and unremarkably felt like Superman compared to my performance on the mountain bike, but only about half of the difference was attributable to differences in tire width and bike weight. The rest resulted from my seat post having gradually slipped downward by about 3 cm or so on the mountain bike. Raising the saddle on the mountain bike let me push a higher gear and climb far better than I had been.
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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