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Broken Derailleur Hanger

Last updated on December 23, 2014

For the first time in my life, I’ve broken a derailleur hanger. Yesterday when riding at Bald Mountain Recreation Area, a few miles from my car which was parked at Addison Oaks, I heard a thunk and looked down to see the derailleur in a rather awkward, unhelpful position (photo). Sunset was coming soon, and while I had lights the Oakland County Police who patrol Addison Oaks† are not fond of those who are in the park after dark, so I had to do some quick thinking to get back to the car.

Along with breaking the derailleur hanger, the derailleur cage itself was twisted, so I figured there was no way to get rolling without making the bike a single speed‡. I removed the derailleur, strapped the cable and housing back, broke the chain, and re-connected the chain in the best gear combination I could identify for decent chain tension. While there were occasional shifts up and down the cassette as the chain bounced, this worked well until I was climbing the final hill before Lake George Road.

With a bang the chain had ridden one cog on the cassette higher than intended, tensioning the whole assembly so tightly that I couldn’t turn the cranks. Opening the quick release rear skewer transferred tension to the skewer, bending it, and making things worse. Since the bike would freewheel my only choice at that point was to walk the bike out, hopping on to coast down hills. Thankfully I was only two miles from the car at this point.

I’m still not exactly sure what happened to cause the break, but I can’t help but suspect that yesterday’s crash had weakened it somewhat. Even though was shifting fine and the derailleur appeared straight, I suppose this could have played some part?

Once I got home I set to fixing the bike, and thanks to having a spare derailleur (leftover from making the El Mariachi a 1×9) and basic parts like a spare derailleur hanger, chain, and cable, I was able to get the bike working nicely again. It also gave me a good reason to wash the bike and clean Orange Seal residue from the tubeless valve stems. When the chain bound one cog on the cassette became slightly bent, so now it makes a bit of noise when riding, but it wasn’t noticeable on a test ride. I’ll try to bend it back when I next have the cassette off the bike.

The photo above shows the broken derailleur hanger, and what I believe to be plastic deformation. I find the stretching of the laser etched “Wheels Mfg Droput-25” logo to be particularly fascinating, as it shows how the aluminum stretched before failing. The thin, torn off sliver is interesting to me as well.

After the work my bike is back in order, and while everything seems in place, I need to give it a shakedown ride before I’m willing to take it out on remote trails. With luck I’ll be able to squeeze this in tomorrow morning.

† It seems that junior / trainee officers are regularly assigned to Addison Oaks, and they seem to take a hard line which makes them less than pleasant to deal with. While a broken bike likely would have been a fine excuse for being in the park after dark, I didn’t want to deal with this.

‡ In retrospect after inspection at home, I probably could have gotten the bike well enough to ride out with a new hanger. I’d have had to deal with a bunch of mis-shifts, but at least I wouldn’t have bound the chain and had to walk. This is what I should have done… Oh well, at least it was a nice day and now I have a story.

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