How to Measure and Replace Your Bike Chain
Chains “stretch” over time when the pins and bushings start to wear down, which can cause skipping. If your chain needs to be replaced, you should find out right away—otherwise you’ll be faced with that disconcerting sensation of having your pedal jump forward while you’re trying to climb.
Checking Your Chain for Wear:
Daryl Robbins, bike mechanic instructor, recommends you have a chain tool on hand to check whether it’s time to replace a worn-out chain, but this can also be easily measured by Sheldon Brown’s ruler trick. Here’s how: Place a 12-inch ruler along the bottom of the chain and line up the 0 with the center of a chain rivet. Look at the center of the rivet located 12 complete links away. On a new chain, the rivet will line up exactly with the 12-inch mark. If it’s off by less than 1/16”, the chain is showing wear but can still be used. If it’s off by more than 1/16”, you need to replace your chain. Don’t forget to check out your rear cogs for wear as well—worn-down cogs can also cause skipping, even with a new chain.
Replacing Your Chain:
You’ll need a chain tool for this. This will support the chain while you press out the little pin holding one of the links together. Align your chain in the tool so that the tool’s pin lines up with one of the chain link’s pins. Turn the tool’s crank until the link’s pin is pushed out, unscrew the tool and remove the chain, which should now be separated.
Now measure your new chain up against your old one to determine how many links you need. Generally, you’ll have at least a chain-length longer than you need. Thread the new chain through the derailleur and onto your cassette. Reconnect by reversing the process you used to pop out the pin on the extra link.
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