Derailleur Hanger Alignment
The aim of this blog post is to assist bike owners, home bike mechanics and shop bike mechanics on how to adjust their derailleur hangers. Didn’t know derailleur hanger alignment was a thing? Don’t worry, we’ll talk you through it step by step and let you know all the equipment you’ll need.
A bent derailleur hanger will result in poor shifting performance. A bent derailleur hanger will be the result of the bike that has fallen over on the right side or from an “off”, in which case the derailleur hanger will bend under the stress, or in the worst case scenario, break. If you replace a bent or broken mech hanger with a new one, you may find shifting issues, so here are the steps for rear derailleur hanger adjustment.
What you’ll need:
- Hex wrenches
- Park Tool DAG-2 or DAG-2.2
- Ideally, an M10 x 1.0mm tap to clean the threads.
How to align your derailleur hanger:
- The bike should be mounted in a repair stand, with the wheels being level - as they are on flat ground. You must check that the rear wheel is mounted straight in the frame, but the wheel does not need to be dished for tool use.
- Remove the rear derailleur, insert the DAG 2.2 and tighten the handle. (It is suggested that a tap is used to chase and clean the threads if needed).
- Rotate the arm towards the left side of the rim, also known as the 9 o’clock position.
- Then rotate the tire valve to the 9 o’clock position - Use the same point on the rim as a constant reference when you are checking your derailleur hanger.
- Follow by loosening the sliding gauge knob and then move the sliding gauge to contact the rim and then secure the knob.
- Slide the gauge bracket towards the hub, before rotating the arm. This will prevent the gauge from being forced against the rim.
- Rotate the DAG 2.2 tool and rotate the rim valve 180 degrees to the 3 o’clock position. Finish off by sliding the indicator towards the rim to the same point near the valve.
- The result of this should be that the gauge is barely touching the rim and that the hanger is aligned horizontally.
- If this isn’t the case and instead the pointer is distant from the rim or the pointer is poking towards the inside rim, it means the derailleur hanger is misaligned and needs to be corrected. You can spot this issue earlier by identifying the gap between the rim and the gauge.
- If the pointer is striking inside the rim, you can reset the tool at the 3 o’clock position and rotate it back to the 9 o’clock position, which will create a gap between the rim and gauge.
- The key is to keep checking when re-bending the derailleur hanger, which will allow you to have more control over the amount of bending that needs to be done. Keep bending until the gap is less than 4mm.
- After aligning horizontally, check the 6 o’clock and 12 o’clock positions.
- When you have checked these positions and the gap is less than 3mm, bring back to a 3 o’clock position, and if the three points are 90 degrees apart and have less than a 3mm gap each, then this means your hanger is aligned.