Broken rear derailleur or busted derailleur hanger? What now? Before you reach for your phone and call for a ride, you may be able to turn your rig into a singlespeed and pedal home. Tools required include a chain tool, Allen keys and preferably a quick link.
Step one is to open your chain. If you’re using a powerlink or other quick link, this should be easy. If not, you’ll need to use your chain tool to break the chain. Now un-thread the chain, pull out the rear derailleur cable and remove the rear derailleur.
Next select a gear where the chain line is straight (usually the small chainring and the middle of the cassette), then put the chain back on, and reattach it with either the quick link or using your chain tool.
You should now be good to go. Just know that this system will be weaker than your previous set up, so avoid putting too much pressure on the chain when pedaling home.