Barry2 

You pays your money and takes your choice.

iamLefty

It’s actually been realigned at a bike shop and the bike shifts fine. But since it’s been bent before, i just want to replace it with a new one.

smd4

Gotcha.

maddog34

from the looks of the pic he posted... it needs aligned... .bent in towards bottom, and front to back is out too, but not as badly as top-bottom.

sometimes the frame/dropout is bent and that can't be solved with a new hanger, eh?

a Worn dropout can also cause mis-alignments.

icemilkcoffee 

The picture he showed was the bike with the existing bent hanger. He wants to replace that with a new hanger. There is generally no need to bend a new hanger.

I do agree with smd4 that typically you can bend a bent aluminum hanger back. I did that with my son's bike while I was waiting for the new hanger to arrive. It worked and I didn't even need the replacement hanger

oldbobcat

Straighten the old one. If you only bent it once, it isn't that bad, and it can take another hit or two like that. And keep the new one for a spare.

Kontact 

You shouldn't, but many of these thin hangers and imperfectly molded dropouts don't end up straight. You can certainly just try it and see if you shifting is off. A bent hanger, not matter what direction, will cause the shifting to fail to go all the way across the range.

As Dedhed mentions, a rear QR wheel uses an axle of the same thread as the hanger, so you could thread a spare wheel in and see if the wheels are parallel (being careful to support the wheel's weight), or use a bare axle and get it to parallel the hub of the rear wheel.

The screws don't matter. Alignment is just bending.

iamLefty

Like what RJ the Bike Guy did? Yeah, i’ve seen him do it on youtube. Seems that could damage the thread though if one is not careful or experienced.

Anyway got a couple questions. Would a bent hanger do any harm to the wheel? This is a new set of wheels i installed recently. Also, if i decide to replace the rd later on, a Tiagra 4700 rd is compatible with a Tiagra 4600 shifter, right? Currently using 4600 shifters and derailleurs.

Kontact 

I don't know why the threads would be any more at risk then when you screw in the derailleur. But a wheel is heavy and you'd want to be careful to not let it go and bend the hanger. I use a bare axle with a nut at home.

4600 is compatible with all the old Shimano stuff, 4700 is compatible with the 11 speed stuff. They aren't compatible with each other.

iamLefty

Good thing i asked. Thanks.

grumpus

That's not a dropout, it's a replaceable derailleur hanger. The dropouts are the frame or fork ends that locate the axle.

Camilo

A shop will do it for a minimal fee. If you want a tool for occasional, rare use, get one of the $25 ones from EBay or Amazon. They work fine for casual, occasional use, at least that's my personal experience.

I agree with two things that have been written:
1 - align the new hangar, and check alignment on any bike that's been dropped or crashed, or isn't shifting perfectly
2 - get a spare. In other words, in this case, one to put on, one to keep as a spare. If they do get bent, it's not unusual for them to break when you straighten/align them

Oh, and 3 - it's called a derailleur hanger, not a drop out.

Kontact 

The last shop I worked at charged $25 an alignment. By all means buy a tool.

If you're cheap, buy two rear axles and a couple of nuts or cones. Make one axle and nuts/cones as a dummy that will go in the dropouts using your QR. Take the other one and tighten two nuts together 1cm from the end, then turn that short end into the hanger from the inside. Now you have two axles 3cm apart that should be parallel. By eye; looking down, up and from the back; make them parallel. Done. You can probably find some beat up hubs or axles for next to free.

Camilo

I agree with you - buy the tool and learn how to use it. But I was actually thinking of that sort of charge - $25 and it seems pretty reasonable to me, probably the minimum shop time? For someone who encounters this issue very rarely (most riders, me included with 8 well used bikes in the family) and doesn't care to amass tools (not me!), even inexpensive occasional amateur-grade ($25-$50 for a cheap one) I think the shop charge is a good deal. Double the good deal quotient if the person has no inclination or desire to do this stuff his/her self (again not me). I have one and have used it a couple of times but only once because the alignment actually functionally out and that was when I bent a hanger falling down (not really a crash). The rest was to just check things because I bought the new tool I like doing my own stuff just because it's fun and I avoid having to deal with uncertain quality and delays at the LBS. But most people have no desire to straighten hangers or buy the tool to do it, so $25 +/- is well worth it. MHO of course.

Kontact 

Really, half the stuff we discuss on this subforum people shouldn't be doing unless they are pretty handy. But if you are so inclined...

Camilo

Yeah, pretty biased sample population. Certainly apropos to the totally balled up measuring ruler vs chain checker thread. There's a good reason there's chain checkers regardless of the mechanics of chain wear.

smd4

Simply ridiculous. Bike maintenance/repair isn’t rocket science.

Kontact 

It isn't. But some people seem to have very little innate handiness or 'empathy' for the machines they are working on. The kind of folks that just tighten bolts down without knowing what they do, can't hang a picture straight or turn the wrench harder when the thread doesn't go in right. In this case, replaceable hangers are often flimsy and connected to very thin carbon dropouts in a way that doesn't tolerate much fumbling. If you've never seen anyone straighten one and you don't have a good eye for making things parallel, you might find hanger straightening frustrating - especially with ad hoc tools.

So I've described how to do it with ad hoc tools, but I'm also warning that my description is for people that at least have a bit of clue about how to use tools.

smd4

Of course, people should know their limitations. I can replace a light switch, but after doing that, and the light still doesn't come on, I call an electrician. Same for A/C or furnace problems. Or plumbing issues beyond cleaning a trap.

To me, aligning a derailleur hanger might be one of the simpler repairs. But if it's outside your wheelhouse, spend the $25 bucks and have it done by a shop.

Kontact 

The difference being that you can destroy a $6000 frameset if you bungle it.

smd4

A good reason to know what you're doing.

Camilo

I dont' think anyone said it is. But do you not agree that many, if not most cyclists, even very enthusiastic ones who ride a lot at a fairly high level, have not desire to do this stuff, have no knowledge how to do it, and might not even have the aptitude to do it. Heck, playing a piano isn't rocket science, but not everyone wants to or even can do it decently if they try.

This group is a very, very biased sample of cyclists and has an unrepresentative proportion of folks who want to and can do bike mechanics. And even here, there's a lot of folks who do not do any of their own work, do not want to, and probably wouldn't be good at it anyway due to lack of interest or basic mechanical experience or aptitude.

Camilo

On the other hand, my experience has been you should be prepared for the hanger to break if it's been mis-aligned by a fall or crash. It's always good to have a spare, it is a part designed to bend or break and it can be tough and take a while to get a replacement.

dedhed

AS opposed to burning down a $550K house?

Barry2 

For the doubters out there, here's a sampling of one.

It's spring cleaning and maintenance time for my backup (wet weather) bike.
I'm converting my 2018 Cervelo R3 from a genuine Cervelo "regular" hanger to a new genuine Cervelo "direct mount" hanger (DRH-SDM).
Left to right the new hanger is out of alignment twice (6mm) the shimano spec (3mm)
Top to bottom the new hanger is out of alignment three times (9mm) the Shimano spec (3mm).

For me at least, it was very worth the check.

All the best

Barry

BTW
IF you do this, remember to lightly grease & HAND tighten the hanger nut, add the wheel and torque the thru-axle, then torque the hanger nut.