Repairing a bent derailleur hanger: This is how it works

If your MTB drivetrain has been meticulously adjusted (e.g. Adjusting the Sram Eagle drivetrain or Adjusting the Shimano gears) is still not working properly, either the cassette is loose or the derailleur hanger is bent. The derailleur hanger can be readjusted using a special tool. Straightening tools for aligning the derailleur hanger are available from 35 euros (e.g. Cyclus Tools at Rosebikes). Good derailleur hanger gauges cost around 70 to 100 euros. It is therefore often cheaper for hobby mechanics to install a new derailleur hanger. Derailleur hangers for common MTB models cost around 15-30 euros. As almost every manufacturer uses its own derailleur hanger or dropout, the choice of derailleur hangers is huge.

With such a derailleur hanger gauge, you can align the derailleur hanger on your bike yourself in just a few minutes. For ambitious hobby mechanics, this tool is a must-have in the home workshop.

Aligning a bent derailleur hanger: Video instructions

Whether it's a harmless fall or space-saving bike transport in the car, an aluminium derailleur hanger can be bent in an instant. This is because the derailleur hanger serves as a predetermined breaking point and is intended to protect the expensive rear derailleur. A small, inconspicuous spare part with a big impact. In most cases, slightly bent derailleur hangers can be straightened in just a few minutes with the right tool. We show you how to do this correctly in the video:

If the derailleur hanger is intact, the derailleur pulleys should be positioned vertically in an imaginary line under the sprocket. Here in the picture you can clearly see that the derailleur hanger is bent inwards at the bottom, which happens quickly in the event of a fall.

You can read more about "DIY wrenching" in the second part of our wrenching series in BIKE 3/19 - on newsstands from 5 February. We also have Eight bike toolboxes from 85 euros tested and explain which standard tools bikers need at home.