48. How To Align a Rear Derailleur Hanger
Derailleur hangers are easily bent and can cause shifting problems.
IMPORTANT: Nuts and bolts on your bike should always be tightened to the manufacturer's specifications.
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50% of the cost of the bicycle featured in this video was covered by your donations. The remaining 50% was generously donated by JensonUSA.
Today we’ll learn how to straighten integrated derailleur hangers. Shifting problems caused by a bent derailleur hanger are quite common. This can happen if your bike is dropped, crashed or bumped, or if it was poorly aligned at the manufacturer. The result is poor shifting even after all other adjustments have been made.
Tools
For this job you’ll need a repair stand and a hanger alignment gauge like this one called the DAG-2 from Park Tool. It costs about $50 dollars. When compared to bike shop labor charges, it will pay for itself after 3-4 uses. You’ll also need a 5mm hex key for the derailleur mounting bolt, and a string or small strap to hold the derailleur out of the way while you align the hanger.
It is important to make sure your rear wheel is true and properly mounted in the frame dropouts, as the alignment tool compares the derailleur hanger to the rim surface. See the tutorials titled How To Remove and Install Your Wheels and How To True a Wheel.
Tool Installation
The first step is to shift the rear derailleur onto the smallest sprocket and then remove the rear derailleur by turning the mounting bolt all the way counter-clockwise. There is no need to remove the shift cable or chain. Then tie the derailleur up onto the frame to keep it out of the way. If you have a replaceable derailleur hanger, you’ll first want to make sure the bolts holding it in place are properly tightened so they don’t move.
Now thread the tool’s shaft all the way into the hanger threads by turning it carefully clockwise into where the derailleur was mounted. If it doesn’t thread in smoothly, the threads may be damaged and need to be chased with a tap. We’ll cover this in a future tutorial. Do not use the tool’s threads as a thread chaser.
We’ll be checking the alignment at four different places on the rim: the 9 o’clock and 3 o’clock for horizontal alignment, and the 12 o’clock and 6 o’clock for vertical alignment. When aligned correctly, the alignment tool’s indicator will be roughly the same distance from the rim at all four locations.
Horizontal Alignment
For horizontal alignment, move the alignment tool’s arm to the 9 o’clock position and rotate the wheel so the valve is at the same spot. Loosen the knob and slide the indicator so it contacts the outside edge of the rim, and then tighten the knob again to hold the indicator in place. Now rotate the tool arm and valve around to the 3 o’clock position and see where the indicator sits. If the tip of the indicator is within 4mm of the rim on this side then the horizontal alignment is ok. If the difference is more or less than 4mm, carefully pull or push the tool’s arm, using it as a lever to slightly bend the hanger in the right direction, and then re-check the alignment on both sides.
You may need to repeat this process a few times until the alignment is within range. It’s important not to bend the hanger too much with the alignment tool. It’s best to bend it a little bit and then have to bend it some more, rather than bending it too much and having to bend it back again.
Vertical Alignment
For vertical alignment, keep the indicator in the same position and then check the 12 o’clock and 6 o’clock positions the same way we did for the horizontal alignment. Always remember to move the air valve along with the indicator and place the indicator at the outside edge of the rim.
Once the hanger is aligned and within 4mm both horizontally and vertically, unthread the alignment tool. Apply a little waterproof grease to the derailleur’s mounting bolts threads and begin threading it back in clockwise. Make sure the B-screw adjustment is sitting behind the derailleur hanger. Then tighten the derailleur to the specified torque, usually around 8-10 Newton Meters or 70-90 Inch Pounds.
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Recommended Books:
- Zinn & MTB
Mountain Bikes: Maintenance, repair, and troubleshooting. - Zinn & Road
Road Bikes: Maintenance, repair, and troubleshooting. - Sutherland's Manual
Sutherland's handbook for bicycle mechanics on CD-ROM. - Park Blue Book
Hundreds of photos and hundreds of procedures.
Discuss this topic in the Derailleur Forums
13 Responses to “How To Align a Rear Derailleur Hanger”
Feel free to leave a comment...
and oh, if you have a maintenance/repair question, please ask in the help forums.
Recommended Tools:
- Park DAG-2
The DAG-2 accurately adjusts bent derailleur hangers. - 3 Way Hex Wrench
Park 4mm, 5mm, and 6mm hex is comfy and has great leverage. - Folding Hex Set
This compact 1.5mm - 6mm set is perfect for on the road repairs. - Pro Hex Wrenches
Park HXS-1 L-shaped quality hex wrench set. 2mm - 10mm - Park PCS-9
Entry level repair stand for the home mechanic. - Park PCS-4
Uses the 100-5C clamp and includes a leg stabilizing system.
Hey Alex, thanks for another great tutorial. I have tried to align my rear derailleur hanger before but never got it right. Now I´ll try to find this useful tool
Take care,
Ricardo
As always, another excellent tutorial. Your tutorials are the most important tool I have. Thanks, and this coffee is on me. You can even add a little “something” extra to your coffee to give it some kick.
Thanks.
Nice tutorial.
But: you can buy 5 hangers for the same price of the tool.
Hi, Alex
As all ways a first class video on how to use the Park tool DAG 2 I have the Park tool DAG 1 Version the only different is the screw in shaft length on the Park tool 2 the screw in shaft is a little longer than on version one but both versions will work the same.
It does look much better on video as any one can follow your videos on bike fixing very easy and simple with the written list and where to buy the tools is a god send.
Best Wishes Anthony.
@ Ricardo – Glad to hear… thanks!
@ J.Karlik – Thanks for the coffee!
@ Japp – It’s true you could buy 5 hangers for the price of this tool, but it is wasteful to replace parts that are easily repaired. Also, a lot of bikes don’t have replaceable hangers.
@ Anthony – Thanks! I used to use the DAG-1 and I thought it was a great tool too. It was less expensive… too bad they stopped making it
Hey man great tutorial on how to align derailleur and how to use the tool. Keep up the great work.
ossie
Nice tutorial, I didn’t even know you could fix mech hangers (though mine tend to break rather than bend).
Just out of interest what purpose does lining the arm up with the air valve serve?
Thanks Ossie and Jon,
@Jon – Sorry, I should have mentioned that in the video. The valve should line up with the tool arm so the distance is always exact, even if your wheel is out of true.
You do a great job on the tutorials I’ve seen, congratulations.
To Jaap, just because you replace the hanger doesn’t mean it’s necessarily properly aligned for that particular frame. A replaced hanger should always be checked for correct alignment after replacement. It SHOULD be correct but there’s the difference between theory and practice.
Providing the wheel is rotated to the same position eg the tool is aligned with the valve stem at each position, it’s not necessary for the wheel to be especially true as the point out of true will rotate with the tool. That is the reason to rotate the wheel and measure at the same point on the wheel. It
IS however essential that the wheel is correctly fitted into the frame. For this reason whenever I refit a rear wheel I always remove the bike from the stand and do up the QR with the wheel resting on the ground and the bike held vertically. While it’s possible to “pinch” the wheel into the correct position in the stand with one hand while doing up the QR with the other, dropping the bike out of the stand takes only fractionally longer and you can be absolutely certain the wheel is installed correctly. Nevertheless I still confirm by sighting down the stays from behind. It sounds more time consuming than it is in practice but be aware that each time to bend an alloy drop out you’re fatiguing it and bringing it one point closer to death. Replacements may be cheap, but they rarely crack at convenient times, and I’ve seen the results of Mr derailleur becoming intimately acquainted with Mrs Spokes; not pretty!
Hi,
I would like to point out if people are on a budget and would like to buy the Park Tool DAG 2 they can get a similar item that is made by Cyclus Gear Hanger Alignment Tool will do the same job at much lower cost: http://www.wiggle.co.uk/p/cycle/7/Cyclus_Gear_Hanger_Alignment_Tool/5300003490/ .This tool has a very good write up also they do ship international as well or you may be able to get it from your own Country.
Wow Alex you are indeed an awesome guy tuning up my bike there. Hahaha Just joking another great video!
Hi Alex, thanks for the sterling video – very clear and informative to the point I resolved to have a go with doing the repair myself.
I went to my local bike shop ( in Munich ) for a replacement hanger and perhaps to purchase an alignment tool. My German language is far from fluent but by the time I described/shown the fellow what I wanted, he simply asked me to hold my bike firm. He then manually (no tools) pulled and twisted the existing fitting back into alignment… there!
It looks ok to my eyes and it took him barely 60 seconds. Saved me a lot of money – but I wouldn’t recommend it. He said himself it requires a lot of experience, I’m sure if I did the same, the bracket would have snapped off.
Anyway, just thought you guys might find the story amusing… it’s been 2 weeks now since the “repair” so looking good…
AWESOME! Now i can salvage this 05 Marin Mill Valley that someone curbed a couple years ago (been sitting in my shop). Lets just say that this seems a whole lot easier, more accurate and safer than taking a mallet and anvil to the hanger and attempting to bang it straight.
My friend has been having a lot of problems with the hanger on his specialized m2 and i can vouch that $50 is less than hes already spent having the LBS fix this problem.
This may be the next tool to order!
THANKS!
Dave