important: Nuts and bolts on your bike should always be tightened to the manufacturer's specifications.

How to Align a Rear Derailleur Hanger

Derailleur hangers are easily bent and can cause shifting problems.

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.

Related Links

Categories

Discuss this topic in the Derailleur Forums

I've tried searching for YouTube assistance but to no avail. Cycled to the shops this morning and the gears weren't functioning, had a look and something has gone horribly wrong. It's as though the chain is suddenly inches longer than it should be and it isn't holding any tension unless the derailleur sits all the way back (image attached) almost so the chain is touching itself as it travels throu...

Read more

I've got a problem with the front derailleur on my 21 speed mountain bike. The bikes chain keeps moving to gear one or even slipping off the chain entirely on the front when I try to ride it. I use this bike to get around my college campus, so I use this bike every day, so I need this bike to work. The bike in question is a 1996 Marin bolinas ridge mountain bike I got at a garage sale years ago ...

Read more

I'm brand new to bike maintenance, and I have incredible difficulty getting my front derailleur to shift into the third (highest) gear, and then staying there. I don't know if the problem is with the shifter or the derailleur, and I would really appreciate any help. derailleur: shimano (that's all I know about it) shifter: a cheapy gradient thumb-knob shifter. No clicks, no numbers, just a - and...

Read more

where to start?

posted 1 year ago

Bought a bike from our neighbor for my husband, 1990ish Schwinn Woodland. When he tried to ride it, realized it doesn't shift gears at all. Where do we start to look at what could be wrong?...

Read more

I fell from my bike at quite the speed, I got injured pretty badly and this happened to my bike as well, is there a way to fix this or do I need to replace https://imgur.com/a/xlGbC...

Read more

Locked up Shimano SG-7C18

posted 1 year ago

Hi. I just bought a used bike and had to change the inner tube in the back wheel. Putting the wheel back on I forgot to reattach the brake arm. I jumped on the bike and almost immediately the wheel locked up. I've taken everything apart and put it back together again, but the wheel just won't move. Does anyone know what I messed up here?...

Read more

This concerns a Shimano Tiagra 4600 2x shifter. There is travel remaining in the rear deraileur, but none in the shifter itself. I can't reach the two biggest cogs using either of the front chainrings. I did dump the bike, albeit not hard. However, that accident caused the shifter housing to become out of line with the handlebars. I suspect either my repair efforts or the crash have damaged t...

Read more

MTB Ghost Shifting fix

posted 1 year ago

First bike in 7 years and I'm recently experiencing Ghost shifting, I know little to nothing about repairing bikes and I'm in need of help of how to stop the bike from shifting on its own it is very frustrating and makes it difficult to ride at times...

Read more

I have vintage Charger brand gear levers and I am wondering if they'll work with Suntour VX derailleur as well as derailleurs that say index system....

Read more

From 1st to 2nd-problem

posted 1 year ago

Hi. Sorry I dont know if this is in the right section of the forum. I just got a mtb for the 1st time as an adult. On the left hand side of the handle bars where you can change for 1 to 2 to 3. When I change from 1 to 2 it doesnt alwaya do it. The dial moves to 2 but the bike makes an awful noise and no matter how much i pedel it still makes that noise. If I then go into 3 it then after a good ...

Read more

I am riding a Bianchi 928 with SRAM Red components.  I have a 10 speed 11x28 cassette.  I am replacing my rear derailleur since the guide pulley cogs are now worn to sharp points.  The present derailleur has a short arm.  SRAM seems to have 3 sizes of derailleur arms for a 10 speed cassette; short, medium, and long.  The 28 cog gear still works will with my short derailleur.  I heard that yo...

Read more

I have a Deore LX shifter like on this photo The push button at the bottom doesn't catch the piece inside unless I press slightly up when I shift. Is that fixable or do I have to change the part? Thanks!...

Read more

Yesterday 5 meters away from my destination my rear derailleur suddenly "snapped". I though at first that the cable broke, but no. I flipped the bike around and started shifting and it looks like it kinda "works" but it suddenly doesn't want to shift into the lowest gear (the biggest gearsprocket). I rode back home just fine, but I am a little bit worried and I am not sure what happened. It is a ...

Read more

Trouble fixing gears

posted 2 years ago

Hey, i hope this is the correct subforum The bike gear cables broke and Im trying to replace them. BUt it's my first time, and I've run into some trouble. I can't seem to get the correct tension in the cable, or there's something wrong with the thing thats supposed to shift gears. I took a video of it. The same tension works for two different positions in the gear shifter thing. How do I fix this...

Read more

I have a problem on my Front bicycle derailleur. I'm new to bike repair so I'm not sure of using the right terms. The chain is on the largest chainring in the front and when I use the small pusher on my shifter, I can hear a click but the chain doesn't move to a smaller chainring. I read online some advices and I removed the cover of my shifter, I put WD40 first, waited a long time, then put tri...

Read more