This video will focus on derailleur hanger alignment.
We'll walk through how to check and correct any issues.
Hello, Calvin Jones here, Park Tool Company.
Poor shifting performance can be caused by many factors,
but one that's often overlooked is a misaligned derailleur hanger.
This small piece of metal is the attachment point between the bike and the derailleur.
If it comes out of alignment, it can typically can be re-bent into position.
When the derailleur hanger is straight, it ensures proper derailleur-to-cog alignment,
which is the first step towards proper shifting.
A strong impact on the derailleur can cause the hanger to bend
and when the hanger is bent, the derailleur's guide pulley becomes misaligned to the cogs,
and poor shifting is the result.
Damage on the drive side of the bike is a good clue to check hanger alignment,
but it's also important to check newly installed hangers as well.
If the hanger is misaligned, making other adjustments -
such as to the limit screws or barrel adjusters - will not be effective.
Always check derailleur hanger alignment first, at least by sighting the hanger.
If you're out on the trail and need a temporary fix, you might just pull until it looks straight.
But in order to get a clear diagnosis, and an accurate repair, you'll really need a derailleur alignment gauge
such as the DAG-2.2.
Here's a quick explanation of how to use it.
In order to make the plane of the hanger parallel to the plane of the cogs,
the DAG-2.2 effectively extends this plane to the rim.
So we'll measure the distance to the rim as shown, then lock this measurement by tightening the knob.
We then rotate the tool 180 degrees.
If this gap is larger than 3mm, we know our hanger needs a bit of straightening,
so we bend and re-measure our distance to the rim.
Now the gap is less than 3mm, so we move to check the perpendicular axis.
If our gaps are less than 3mm, our work is complete.
A 3mm gap at the rim means the hanger is roughly half a millimeter out of alignment at the sprocket -
that's where the shifting actually happens.
Notice we always measure to the same place on the rim.
Doing this takes wheel trueness and dishing out of the equation.
A good rule is that if the hanger survives the repair process, it'll have the strength to do the job on the bike.
In extreme cases, it's possible that your derailleur hanger can fail during the repair process.
For this reason, it's a good idea to keep a spare hanger on hand.
There are many different models of derailleur hangers,
and it can take time and research to source a compatible hanger with your bike,
so obtain a spare before you really need it.
If your bike has obstacles such as racks or fenders, simply set the O-ring on the indicator to contact the tool.
Loosen the indicator knob and pull the gauge back to clear the obstacle.
Return it to the reference point set by the O-ring.
Alright, let's walk through the process from the beginning.
Mount the bike in a repair stand and level it to the ground.
Check that the rear wheel is mounted straight in the frame.
Remove the rear derailleur by loosening the mounting bolt at the hanger.
Install the DAG-2.2 and tighten the handle, paying special attention to not cross-thread the tool.
If it is difficult to thread in the tool, there may be bad threads in the hanger.
Chase and clean the threads using a 10mm tap such as the TAP-10.
The typical derailleur hanger design is easier to bend vertically than horizontally,
so corrections made horizontally can also affect vertical alignment.
For this reason, we'll correct the horizontal axis first.
Rotate the arm of the DAG toward the right side of the rim, at the “3:00 o’clock” position.
Rotate the wheel so that the tire valve is in line with the tool.
Use this point on the rim as a constant reference when checking the hanger.
Move the indicator to contact the rim, and secure the knob.
Slide the gauge bracket towards the hub before rotating the arm.
This prevents the gauge from being forced against the rim.
Rotate the tool and valve stem 180 degrees to the 9 o'clock position.
Slide the indicator toward the rim to the same point near the valve.
If the gauge barely touches the rim or has a small gap - less than 3mm - the hanger is aligned horizontally.
Use a 3mm hex wrench to gauge the gap.
If the indicator is more than 3mm from the rim, the hanger will need realignment.
Correct this by bending the hanger using the DAG-2.2.
Bend enough so that the gap is roughly half as big as before.
If the indicator strikes inside the rim, the hanger may be misaligned and it may need to be corrected.
However, it's easier to determine the error by seeing the gap between the rim and gauge,
so reset the tool to contact the rim at the 9 o'clock position.
Now check the gap at the 3 o'clock position and measure.
Bend the hanger using the DAG-2.2 so the gap is half as big as before.
After bending, recheck both sides.
reset the gauge
and remeasure the gap.
Repeat bending and checking until the gap is less than 3mm.
When the horizontal positions are aligned, move on to check the vertical alignment.
Keep the same setting on the indicator and bring the tool to the 6 o'clock position.
If the indicator is within 3mm of the rim, the process is complete and the hanger is aligned.
Otherwise, set the indicator to the rim, and then check at the 12 o'clock position.
If the gap exceeds the 3mm tolerance, bend in small increments, rechecking and resetting the gauge.
When the gap is less than 3mm, keep the same setting and check again at the 9 o'clock position.
When three points that are 90 degrees apart are within 3mm, the hanger is aligned.
Remove the tool and reinstall the derailleur.
And that concludes the process for derailleur hanger alignment.
Now that the hanger is properly aligned, you will need to check your derailleur's limit screw and index settings.
See this video to walk through the process.
and finally, be sure to checkout the Park Tool guide to derailleurs
for an overview of all of our derailleur and shifting content.
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