“How to find the right derailleur hanger?” you may ask yourself when trying to choose the correct replacement from over 400 similar looking gear hangers. In this article we will have a look at how to remove and fit a gear hanger and find a compatible replacement.
If the rear mech has an impact it generally snaps or bends at the weakest point, that is the gear hanger.
What is a derailleur hanger?
A gear hanger is a sacrificial part of aluminium and carbon frames made out of an aluminium compound.
It connects the derailleur to the bike frame and it’s designed to bend or break during an impact to protect the frame from being irreparably damaged.
The rear mech is attached to the bottom of the hanger and the top of the hanger is attached to the frame.
Tools required to remove derailleur hanger:
Set of allen keys.
Crank nut wrench
Barrier cream or gloves.
Cable tie or strap.
Removing a derailleur hanger
- Put the bike on a stand.
- Remove the rear wheel.
- If the hanger is in one piece, then with your left hand hold the rear derailleur and pull it back so that the B-tension screw on the derailleur is clear of the B-tab on the hanger.
- With your right hand grab a 5 millimetre allen key and unscrew the mech bolt anticlockwise until the derailleur is free from the hanger.
- Put the mech next to the right chainstay and secure it with a strap.
- Now unscrew the bolt(s) that secure the hanger to the frame. For the single bolt hanger use a crank nut wrench to hold the back nut.
- Put the hanger aside as you will need it to find the matching replacement.
- If the hanger is broken then hold the arm and the body of the rear derailleur in one hand and using a 5 millimetre allen key, unscrew the mech bolt until the hanger is no longer attached.
- Put the bottom part of the hanger aside.
- Put the mech next to the right chainstay and secure it with a strap.
- Now unscrew the bolt(s) that secure the top part of the hanger to the frame. For the single bolt hanger, use a crank nut wrench to hold the back nut.
- Put the top part of the hanger next to the other broken piece.
How to find the right derailleur hanger?
Derailleur hangers come in many different shapes. Some of the hangers are more universal and used on different bike makes and models.
Others are specific to the particular brand, model and year.
So how to find the right derailleur hanger?
If you know your bike details such as make, model and year of manufacturing you can contact an authorized bike dealer of that specific brand.
Some bike manufacturers sell replacement parts directly from their website. Always compare the recommended replacement part with the broken hanger.
Some hangers are almost identical, however you can identify the correct one by checking the following details:
- The nose.
- The top of the hanger.
- The hole fastening position.
- The cutaway.
If any of these features don’t match the hanger will most likely not fit.
If you still can’t source the spare bike hanger or you don’t know the details of your bike you can visit the website of specialist suppliers of rear mech hangers. To help you find them I’ve attached some links below:
When looking for a replacement hanger check these details to narrow your search.
- First check how your rear wheel fits into the dropout. The hanger with a standard axle will have a hub socket
and the one with thru axle will have a hole.
- Check which way the hanger attaches to the frame.
This will define whether the cutaway is at the front or at the back.
Cutout at the back 
Cutout at the front
- Now check how many fastening holes there are. The design of the frame will define the number of fastenings. Most hangers will have between one to four.
- Once you know these details check the supplier’s database to find the correct replacement. Compare the recommended replacement part with the broken hanger. To make sure that you order the correct one
How to find the right derailleur hanger – Fitting a replacement.
Once you have your hanger it’s time to fit it.
- Slot the gear hanger into the correct position.
- Fit the fastener(s) and if there are more then one tighten them sequentially clockwise. For the single bolt hanger use a crank nut wrench to hold the back nut while tightening.
- Remove the mech from the chainstay and place the derailleur bolt against the hole on the hanger and twist it up slightly so that the B-tension screw is clear of the B-screw tab.
- While still holding the derailleur, place the 5 millimetre allen key into the derailleur bolt and gently screw it in clockwise.
If the bolt resists then don’t force it as you might cross thread the hanger. Keep adjusting the angle of the derailleur bolt and repeat the tightening process until you are successful.
- Replace the rear wheel. If you’re unsure how to do this we have a great article here for the wheels with a standard axle.
Our article here will guide through the process of refitting the wheel with a through axle.
You can also check this video to see how to fit a rear wheel in few simple steps.
Only aluminium, carbon and some titanium frame bikes with derailleur gears have mech hangers. A derailleur hanger is designed to bend or break during an impact to protect the frame from being irreparably damaged.