As the “victim” part of the bike, the mech hanger snaps or bends in a crash to protect the frame (and sometimes the mech) from damage. It connects to the drive side release and mechanically connects the rear to the edge. If you find yourself out of place after a recent bump or fall, the hanger may be bent and needs to be straightened. That’s it…
1. Check your mech
First, check that your derailleur is snug on the derailleur hanger (turn the bolt clockwise with a 5mm Allen key).
Place the bike upside down on the bench and move to the flywheel’s center. Look down at the gears to see if they line up with the chain.
2. Remove the mecha
The mecha cage will not fit the chain if the hanger is bent. As long as it’s only a few degrees off, you should be able to straighten it.
Note the direction that needs to be adjusted. Shift to the smallest sprocket, loosen the mounting bolts, and remove the mechanism from the bike.
3. Align the hangers
At this stage, a hanger alignment tool will come in handy (if you can’t find it, skip to step five).
Screw the tool clockwise into the hanger until it is tight. Adjust the arm until it is flush with the rim at 6 o’clock, then turn the wheel and tool 180 degrees (12 o’clock).
4. Check the alignment
If the tool is off the rim, gently push it towards the wheel until the tab is permanently bent back. Check again at 6 o’clock until the device is flush in both parts. Repeat this process at 3 and 9 o’clock.
5. Align with a wrench
You can use a large adjustable wrench if you don’t have an alignment tool. Tighten the twist on the bracket to cover the threaded holes and clamp the frame. Then turn the wrench slightly until the shelves are realigned.
6. Reload the mech
Check by eye that the hanger is straight. Avoid overcorrecting the bend, as this can weaken the hanger.
Reinstall the mechanism, move it to the center of the cartridge and recheck the alignment, as in the first step. Remove the mech and try again if the hanger is still not straight.
7. Check the circuit
With the hanger straightened, check the shifting by shifting through the gears. You may need to re-adjust the cable tension and restrain the screw from getting it to work correctly.
Straightening the temple can weaken it, so it’s best to order a replacement just in case.