DIY: Checking the Chainline - Tips
When installing a new crankset and/or cassette, it's important that you double check the chainline. This refers to the imaginary line from the chainrings to approximately the center of the rear cassette.
Here's how to do it.
1. Set the rear derailleur to the middle gear (#5 on a 9 speed, #5 or #6 on a 10-speed).
2. View the chain from the rear or front of the bike and confirm that the chain is straight, and not bent to one side or the other. It should look something like this:
3. Switch the front derailleur to the different chainrings and repeat the inspection for each chainring.
If there is an excessive angle, the chain will eventually get worn out prematurely. In order to get the chainline straight, you can shim either the cassette or crankset with a shim, however we're covering this in a separate DIY article for the more advanced user.
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