How to replace your Gear Mech Hanger

Step by Step instructions

If you’re unsure, always take your bike to a qualified cycle technician who will be able to fit your new derailleur hanger and offer advice on the the overall state of your drivetrain. 

This process is fairly easy and can be carried out with normally just a 5mm allen key on std hangers, and smaller allen key sizes on others, just follow these simple steps, and your be back on your bike in no time. If unsure, always contact your local bike shop for expert advice.

• When installing a replacement mech hanger, be sure to clean and inspect the frame dropout for damage. Do not install a replacement hanger onto a damaged frame dropout. If not sure, please always take your bike to your local shop for advice.
• Clean the surfaces and apply a light film of bike grease to the dropout to minimize noise or “creaking.”
• Apply Loctite if desired (but not a must) and tighten the hanger nut/bolt.
• Over-tightening screws may strip hanger threads, so please be careful, these do not have to be super tight.
• Check to make sure that the hanger screw ends do not make contact or interfere with the rear sprocket or chain. File the protruding screw end if necessary.
• Re-attach the rear derailleur to the mech hanger and check the high and low limit adjustment screws and the index adjustment (where applicable). Be sure to re-adjust the quick release making sure the wheel is straight in the frame.
• In many cases, a broken hanger could be a sign of a problem with one of the chain links, so unless you check this, the new hanger could fail again due to over-tension in the chain. If unsure, always take your bike to your local cycle shop for expert help and advice.

What is a bent gear mech hanger?

Most frames are equipped with a replaceable derailleur hanger. This part is installed as a safety feature, as well as a convenience to you.

It is not uncommon for foreign objects, such as sticks, stones and other debris to bend your hanger. A bent hanger can occur from shifting hard under load, and/or transporting your bicycle. Cycle derailleur hangers are designed to bend and break!

This inherent design actually keeps more expensive damage to your frame from occurring.

If these were stronger and more resistant to bending and breaking, there is a good chance that these forces would bypass the hangers and destroy the area of the frame attached to the hangers.

It is a good idea to purchase a few extra hangers to prevent a breakage from interrupting your riding time.

If your rear derailleur is shifting poorly, not staying in gear, and appears to be bent or out of alignment, check first whether the derailleur hanger is bent.

The derailleur hanger is the piece of metal that the rear derailleur attaches to near the rear axle. On most bikes this is a replaceable piece of aluminium which is designed to bend or break when stressed rather than causing costly damage to your bike frame.

Typically the derailleur hanger is supposed to be at right angles to the ground when seen from behind. Any deviation from this line will cause your shifting will be “off,” because the chain will be pulled through the pulley wheels at an angle.

Because the piece is designed to break, bending it back ‘straight’ will stress it further, probably causing it to snap, If possible live with it until the ride is over and you can get it replaced. Or better still carry a spare with you !

Adjusting the high and low adjustment screws on the derailleur may allow you to stay in gear, but the chain will still have a tendency to slip

If the chain skips really badly, you can try to bend the hanger back, grab the derailleur body (not the pulley wheels) and apply firm constant pressure to bend it in the required direction. An alternative is to remove the derailleur with a 5mm allen key and run your bike in a ‘single speed mode’ by adjusting the chain length, this is not ideal but is a good solution to get you home.

Even if you do manage to bend the hanger straight, it may retain a lateral (front-rear) twist, which will still keep it from shifting perfectly

Once you get back home, buy a new hanger. The stresses of being bent and bent back mean that your current one is weak and could disintegrate at any time.

Thank you very much
The GearMechHanger.com Team