Bent derailleur hanger?
 

Hi all. My bike fell on the drive side and immediately thereafter, there were shifting issues. This happened while I was out on a long ride and using the barrel adjuster got me back to I'd say about 97%, but there are still issues. I am assuming the hanger is slightly bent. My eyes are far from expert, and I'm not able to tell by sight if it is bent. I understand from reading that the eyes aren't necessarily the best tool for judging this.

I've been acquiring tools as the need has arisen to become as self-sufficient as possible. I am trying to figure out the most sensible option here. It seems one option is to get a Park Tool (or other manufacturer) derailleur alignment tool which seems that it will aid me in determining if it is bent as well as act as a suitable lever to help get it straightened out. Those tools are not terribly inexpensive. I have only two bikes to maintain, and (knock on wood) this is the only time this has happened in about 8 years of owning this bike. It wasn't my fault, FWIW, but no matter - I understand this can happen at any time, for a variety of reasons. A benefit of doing this is that I'm set for the future, though I hope the usage will be rare.

Another option, I think, is to just acquire a new hanger and replace it. Is that a reasonable option here? Or would seasoned wrenches recommend the alignment tool? Are there other options I should consider?

Thanks for any help you might have to offer.

A new hanger should be aligned as well when replaced.
I personally haven't found the need to buy the tool and pay the shop $15-20 to align a hanger the few times I needed it. That has always been "while I wait".

Having a spare derailleur hanger isn't a bad idea as sometimes a replacement is hard to come by with so many different configurations out there.

I purchased the Alignment tool and have found an interesting fact.
The tool is NOT battery powered, it's powered by IPA.

I've aligned more hangers on other peoples bikes (for a 6 pack) than on my bikes.

It really is a handy tool to have!

Barry

Owning the alignment tool seems unnecessary, given how rarely it gets used, but my local shop is cool about letting me use theirs. I do, however, carry a replacement hanger for each bike. While they sometimes have to be aligned as well, at least you can get home should you bend or snap off an existing one.

If the hanger is out enough to cause shifting problems you should be able to see it. What helps is being very familiar w/ what 'straight' looks like. If the bike falls over and you immediately have noise and shifting issues that get worse as you go to bigger cogs it's absolutely a hanger alignment issue.

The shops I worked at always included hanger alignment with any rear derailleur adjustment. The extra time to remove the unit, adjust the hanger, and reattach the unit always beat the time wasted trying to adjust a derailleur with a bent hanger. Often, after realigning the hanger, the derailleur was already adjusted correctly.

As for hanger replacement, that was usually necessary only after a hard hit or two.

Thank you all. I forgot to mention the obvious other option - visit my LBS. I think that is what I will do in this case. I will also pickup a spare hanger to keep on my bike. Thanks, all, for the great advice.

If you have a QR front wheel, the axle thread is the same as the hanger's (10 x 1). You can thread the axle into the hanger and check for parallel between the two wheels. Some say they use the wheel as an alignment tool, but I found the axle threads aren't good enough for that. Use a large crescent wrench for bending.

Once I had to use a long straight edge on the face of the hanger as a gauge and that worked better than eyeballing it, but not perfectly.

Keep in mind bending aluminum always bears the risk of snapping the piece.

And of course, buying the spare hanger is a great way to assure you'll never need it.

When you buy the spare hanger make sure to have it aligned to your frame. The hanger will be perfectly flat/straight but it has to be straight when attached to your frame, not sitting on the counter. I have to align a sizable percentage of new hangers I install on frames.

Is it kosher to stick an Allen wrench in the bolt hole on the hanger mount bolt and use the wrench to straighten out the hanger? I started out by removing the RD and using a Crescent wrench. Then I saw how easy it was to bend the hanger so I just used the wrench with the bike assembled. Made it easy to eyeball the drivetrain for straightness. My wrench has a handle that provides a good grip.

Kosher no, I don't think it has anything to do with Jewish Dietary Law but I can say they make tools for the purpose. A hex wrench is a tool for tightening and loosening hex bolts and those bolts are not there for bending things. An adjustable wrench like one you might find from the Crescent company is not something I would recommend for much precision wise. Get the proper tools and learn how to use them. Don't ruin your bike and tools using them for the wrong purposes.

But it worked so well. The hanger on my Rockhopper bends like putty. The wrench stayed in the screwhead very securely. The screwhead is deeply recessed. I'm wondering if they didn't do that so that a wrench could be used to tweak the hanger.
I've got one of those Park Tool wrenches that has three Allen keys that meet in the middle. It worked a treat. Now the dam shifter runs like a sewing machine.

Some of the newer frames instructions include DO NOT ALIGN THE HANGER.

If it is soft enough to bend just dropping the bike on the side, I'd probably align it. But, it may not hurt looking at the manufacturer instructions.

If it bends that easily, you may want to check it for cracks/fatigue

Definitely worth getting a hangar tool, IMO. Saves a whole lot a dickering around when you can rule that out (or fix it) quickly. Starting around 10 speed and up, I can not align it perfectly.

I have had several frame or bike that I bought new with the hangar out of alignment.

OTOH, we’ve got a bunch of bike between my wife and I, and several are MTBs that don’t always land on the ground in the gentlest of ways. With just one road bike, it may not be worth buying the tool.