Old 05-26-17, 06:37 AM
John E
feros ferio
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Join Date: Jul 2000
Location: www.ci.encinitas.ca.us
Posts: 19,514

Bikes: 1959 & 1960 Capo; 1982 Bianchi; 1988 Schwinn KOM-10;

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Great responses to this thread, which covers about all of the possible causes I can think of. In my experience working at a bike shop and on friends' and my own bikes, by far the most common causes of high gear skip are an elongated chain and -- sometimes resultant -- wear of the teeth of the smallest cog. Measure a span of 24 half-links, from rivet center to rivet center. This length was exactly 12" when that chain was new, and anything beyond 12-1/16" (a mere 1/2 percent elongation) is ripe for replacement.

One more thing to check -- with the torn-off end of a match or paper towel, see if every chain roller spins freely. If any are stuck, they need to be de-gunked or otherwise freed. Turn the cranks backward while watching the chain as it comes off the bottom derailleur wheel. Does it play out smoothly, or do you see any link-to-link bends that are reluctant to straighten out?
"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
Capo: 1960 Sieger (2), S/N 42624, 42597
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069
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