Garage Files: How To Realign A Bent Derailleur Hanger

Position the tool (as shown in the photo) and slide the indicator until it is about 1mm from the outside edge of the rim.
Rotate the tool 180 degrees and make sure that the indicator is the same distance from the rim as it was before. If your wheel is not perfectly true, you should check the same point of the rim in order to avoid any misreading. To make it easier, you can refer to the valve stem. If the difference between these two readings is less than 3–4mm, you may want to leave your hanger untouched and move on to the next step.
Realigning your derailleur hanger is a delicate operation. Be careful when pulling or pushing on the tool and make sure to use as little force as possible. The goal is to just to get it back to its original form without stressing the material. This will minimize any weakening of the hanger. If you are worried that the hanger’s integrity has been compromised, it’s best to purchase a new one.

 

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