Ask a Mechanic: Straightening Derailleur Hangers

This video is our 52nd episode and marks one year of weekly videos broadcast on VeloNews. It has been a pleasure to help viewers to get their bikes dialed in and improve their riding experience.

Question: My bike fell over on the drive side and bent my derailleur hanger. Do you have any tips on how to straighten it back out? From: Peter

Neil Pryde Derailleur Hanger

If you don’t have a spare derailleur hanger, get one now so that you don’t have any downtime when the inevitable happens.

Answer: It is always a good idea to carry a spare derailleur hanger for these occasions. I always buy a spare with any new bike I get so that I’m ready when the time comes. Although, even with a new derailleur hanger, alignment is rarely perfect. Quick release skewer tension can often pull a derailleur hanger out of alignment once the wheel is mounted in the frame.

The only way to really dial in derailleur hanger alignment is with a derailleur hanger alignment tool. Using your wheel as a guide you can see exactly where you are in the alignment process. Checking the alignment at the top, bottom, and back of the wheel, you can get it perfect every time.

But, this dedicated tool is expensive. A less accurate alternative is to use a crescent wrench to straighten a bent hanger. The problem with the crescent wrench is that you need to be careful that you tighten the wrench down tight on the hanger and make sure that the jaws of the wrench extend past the mounting hole for the derailleur. If the bore for the derailleur mount gets bent, you won’t be able to thread your derailleur back into the hanger.

To check your work for either alternative alignment method, eyeball the alignment first and then thread your derailleur back into the hanger and use the pulleys and cage as a guide that you can compare to the cogs above it. If everything lines up visually, you are probably close enough that your rear derailleur will start shifting well again.

Whatever you do, don’t grab onto the derailleur and pull on it to straighten out the hanger. This often leads to bending the derailleur itself, and while it might look straight when shifted into the 11-tooth cog, it will be out of alignment in the bigger cogs, so don’t do it!

Welcome to our Ask a Mechanic column where our expert mechanics Daniel Slusser and Greg O’Keeffe answer your bike maintenance questions. If you have a question for us, please post it on the Art’s Cyclery Facebook Wall or e-mail Daniel directly at daniel.slusser@artscyclery.com. To see more great how to videos click on the highlighted link to subscribe to our YouTube channel and stay up to date on each episode of the Art’s Cyclery/VeloNews Ask a Mechanic Series.

2015-12-16T17:12:10-08:00