Originally Posted by
3alarmer
...best practice is to measure chain wear with a steel ruler between the pin centers for 12 double links. Should be 12 inches. Chains ought to be replaced before they start to wear the teeth on chainrings and cogs, which are more expensive than chains to replace (mostly).
I replace chains at 12 - 1/6". But I do not throw them away. I put them in a plastic bag and label them with that length. When new chains no longer run smoothly, I use those 12 - 1/16" chains, replacing them at 12 - 3/32" with other 12 - 1/16" chains until shifting deteriorates. Then it's time for all new cogs and rings. That takes many thousands of miles. And it's probably high time to upgrade to the next number of cogs.
My TiCycles was set up 9-speed in '08. 3 cassettes for two wheels. 12,000 miles. New chains go on just fine.
Steel tape measures work really well. (I typically start at 10" so a stretched chain might be showing 22 - 3/32") Measure front of pin to front of pin.
Ben