What does a chain checker do that my 12" ruler cannot?
I dutifully follow Sheldon's 1/2 percent elongation rule, use SRAM PC-58 8-speed chains exclusively, and have never broken a chain, although I have broken two rear axles, two left cranks, two frames, a SunTour platform pedal, a front hub flange, and various spokes and toeclips. I have heard enough Shimano chain horror stories to recommend SRAM or Whipperman, instead.
One way to get more life out of your chain is to use larger cogs and rings, instead of today's fashionable compact sets.
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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