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  1. #1
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    Bent rear derailleur?

    For years I have done most of my own wrench work but never had good luck with the front or rear derailleur. This year I decided it was time to change that... so I watched a bunch of youtube videos and have actually done well.

    I bought a bike off ebay about 3 months ago, it had very low miles on it. I've adjusted the rear derailleur a couple times. But every time I look at it, it looks like the rear derailleur is hanging at an angle. The last time I adjusted it I noticed the hanger bolt was loose. I adjusted the derailleur again tonight, nothing was loose. But that angled derailleur bothers me. I looked at my old bike, and it is perfectly vertical. I looked at this thing closely, and from different angles. Nothing looks bent or damaged. Anyway, I attached a couple photos. Is that angle normal or, Ok? If not, what could cause that? The hanger? It's so short, I don't know how that thing could bend.

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  2. #2
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    No, something's bent, probably the derailleur hanger. The derailleur pulleys should be in perfect alignment (parallel) to your cassette cogs.

    Park makes a great tool for checking the alignment and adjusting it.

    Park Tool Co. DAG-2 : Derailleur Hanger Alignment Gauge : Frame & Fork Tools

    You can "estimate" it and get somewhat close (vertically and horizontally) using a crescent wrench. You just have to be careful though.

  3. #3
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    That looks highly like a bent hanger to me too - the DAG 2 is great but expensive - it can also be fiddly to align if you don't have a high quality work stand that holds the bike very firmly. A decent LBS will be able to sort that out in 5 mins or so if you don't want to buy the tools
    I've never had much luck trying to straighten bent RD hangers without the correct tools it's very easy to twist it if using a wrench - it's virtually impossible to do by eye

  4. #4
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    Quote Originally Posted by SimpleJon View Post
    That looks highly like a bent hanger to me too - the DAG 2 is great but expensive - it can also be fiddly to align if you don't have a high quality work stand that holds the bike very firmly. A decent LBS will be able to sort that out in 5 mins or so if you don't want to buy the tools
    I've never had much luck trying to straighten bent RD hangers without the correct tools it's very easy to twist it if using a wrench - it's virtually impossible to do by eye
    I agree, it's not easy but I've been successful by working slowly with lots of patience. I say that through experience because I've been out on mountain bike trips where I don't have my DAG-2 tool. Check the alignment, make one small bend, check, bend, check, bend.........Eventually you can get it very close. Using a straight gauge, you can eye-ball the hanger with the rear gears pretty close.

    I've bought the DAG tool years ago and it's paid for itself with all the time and frames I've fixed. Even brand new derailleur hangers needed some straightening.

  5. #5
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    Thanks guys. I think I may just bring it into the shop. The frame is carbon fiber, I don't know if I want to mess around with that. And I'm also going to buy a spare hanger.
    Thanks.

  6. #6
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    I thought I'd follow up to this.
    I called a bike shop in town, mainly to ask how long before I'd get the bike back for this type of repair.... but also asked if they could fix a bent derailleur hanger. Their answer was "possibly, but sometimes they break". That kind of concerned me. I could just see them attempting it, saying it broke, charging me for that time, plus for a new derailleur hanger, and charging me 40% more than what I'd pay on the internet for that derailleur hanger. So I just went ahead and ordered one off Amazon. I installed it tonight. Seems like good quality... it's from North Shore Billet.
    Well, as you can see from the photo, it still hangs at an angle. I'm sure it's not bent. Or the original either. I laid them both on flat surface and could not see daylight under them. So I don't know what's going on. The derailleur looks ok. I think it looks slightly better, but that could be my imagination. Man, I'd hate to have to go out and buy another derailleur and just "hope" that that fixes the problem. Suggestions??

    Bent rear derailleur?-derailleur.jpg

  7. #7
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    get a derailleur hanger straighten tool.. I'm guessing it's the hanger tweeked not the derail it's self even with a new hanger often times the frame is'n 100% square to the wheel and you'll get a leaning/lightly out derailleur

    well worth the investment as after my 5mm allen it's my #1 most used tool.. If I ride a rather twiggy or rocky trail and I hear a few things twang off the rear wheel during the ride I just auto check the hanger when I get home now.. saved myself a lot of on trail headaches because I did!!
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  8. #8
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    Quote Originally Posted by thomllama View Post
    get a derailleur hanger straighten tool.. I'm guessing it's the hanger tweeked not the derail it's self even with a new hanger often times the frame is'n 100% square to the wheel and you'll get a leaning/lightly out derailleur
    Sorry, I left out the word "hanger" from my reply. So I edited it.

  9. #9
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    Quote Originally Posted by johnb View Post
    Sorry, I left out the word "hanger" from my reply. So I edited it.
    like I said,.. even a new hanger will still often times be lightly off square with the wheel... you need a hanger straightening tool

    Will cost you less than one visit to the shop.. and you'll use it the rest of your biking life
    Going to try and bring Trail Tire TV back. go take a look... http://trailtiretv.blogspot.com/

  10. #10
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    Quote Originally Posted by thomllama View Post
    like I said,.. even a new hanger will still often times be lightly off square with the wheel... you need a hanger straightening tool
    I'm not against the idea of getting one of those, I'm just concerned about whether it will help or not. I laid the new hanger on the counter and shined a light behind it, there was no light shining underneath the thing. It laid perfectly flat on the counter. Same thing with the old hanger.

    Question on that tool: how does that work? One person mentioned bending the hanger with a crescent wrench. So I leave the hanger mounted to the frame and do that? The frame is carbon fiber... that concerns me... reafing on that hanger while it's attached to the bike.

  11. #11
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    Quote Originally Posted by johnb View Post
    I'm not against the idea of getting one of those, I'm just concerned about whether it will help or not. I laid the new hanger on the counter and shined a light behind it, there was no light shining underneath the thing. It laid perfectly flat on the counter. Same thing with the old hanger.

    Question on that tool: how does that work? One person mentioned bending the hanger with a crescent wrench. So I leave the hanger mounted to the frame and do that? The frame is carbon fiber... that concerns me... reafing on that hanger while it's attached to the bike.
    you're hanger is specially designed super soft alum.. it's made to bend easy so if the derailleur get hit by a stick or a rock the hanger snaps instead of your frame and/or derailleur (thou that usually gets mangled in the wheel after the hanger breaks )

    the hanger tool screw in place on the actual derailleur,.. it has a long arm and a feeler on the end.. the feeler is made to check the actual alignment to your rim-hense the cassette and hub. the issue is a very little amount that you can't even see can make the derailleur flex out and not align with the cassette properly.. After you check for square with the wheel (make sure you rotate the wheel and hit the exact same spot on the rim so any warp of the wheel isn't an issue) you can use it to lightly bend the hanger straight. again it's rather soft material on purpose and as long as you don't go crazy on it it's made to bend a little.

    In all my years and especially now with the mass produced asian frames, the hanger bolting area of the frame 2 out of 5 times isn't really square to the wheel and the brand new hanger needs to be aligned...

    I made a little video about ghost shifting.. it's not exactly your issue but it shows the hanger tool and how it works...

    Trail Tire TV: Fix ghost shifting
    Going to try and bring Trail Tire TV back. go take a look... http://trailtiretv.blogspot.com/

  12. #12
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    Quote Originally Posted by thomllama View Post
    In all my years and especially now with the mass produced asian frames, the hanger bolting area of the frame 2 out of 5 times isn't really square to the wheel and the brand new hanger needs to be aligned...
    Trail Tire TV: Fix ghost shifting
    That's what I was wondering about, exactly. Whether the bolting area was the issue.
    Anyway... you've convinced me! I'm going to order that tool.

    I'll post back here after I've adjusted it with the tool.
    Thanks!!

  13. #13
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    Quote Originally Posted by johnb View Post
    That's what I was wondering about, exactly. Whether the bolting area was the issue.
    Anyway... you've convinced me! I'm going to order that tool.

    I'll post back here after I've adjusted it with the tool.
    Thanks!!
    best investment you'll make,.. well besides the bike it's self

    PS,... sounds/looks from the bits in pics it's a pretty nice ride.. take a pic or two of the bike and post .. we like bike porn here
    Going to try and bring Trail Tire TV back. go take a look... http://trailtiretv.blogspot.com/

  14. #14
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    Well, the saga of the bent derailleur hanger finally comes to an end....

    I received my new Park DAG-2 hanger adjustment tool. 66 bucks at Amazon. Seems like a lot, but would pay for itself, right?
    I watched several YouTube videos on how to use a hanger adjustment tool. There are some good ones on there. I also watched your video.
    At first I didn't quite get it, I would start at the top, then move down 90 degrees, make an adjustment, move another 90 degrees, make another adjustment, go all the way back to the top, and the top was no where what it had been. Probably doesn't make sense. But I figured out you have to make small adjustments as you go, don't try to get it all at one spot.
    I took the tool off and put the derailleur back on. It wasn't better, it was worse! I put the tool back on... took my time more, went through 4 different locations, 90 degrees apart, until they were all the same. Put the derailleur back on. Still off. Way off. So guess what I did? I put the tool back on. Eye-balled it, I knew it had to go in, so I bent it in with the DAG-2.... had to do that twice, put it on, take it back off. But now, the derailleur is perfectly vertical. Check out the pic. So.... the moral of the story is: I could have done this with a rusty old crescent wrench.

    I know, it makes no sense. I have no idea why the tool didn't correct the problem, using it the correct way. I know I did it right, especially the 2nd time around.
    Thanks for all your help. I included a pick of my bike. I don't have any good pictures of it, so that is one from the ebay ad from which I bought it.

    Bent rear derailleur?-derailleur.jpg

    The bike is not setup like that now, with the seat that high, and the stem spacers on top.
    Bent rear derailleur?-top-fuel.jpg

  15. #15
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    Quote Originally Posted by johnb View Post
    ......

    I know, it makes no sense. I have no idea why the tool didn't correct the problem, using it the correct way. I know I did it right, especially the 2nd time around.
    Thanks for all your help. I included a pick of my bike. I don't have any good pictures of it, so that is one from the ebay ad from which I bought it.
    #1 reason people don't get it straight - bent rim or just don't hit the same spot. when you check find a place in the wheel and rotate the wheel so the feeler is always using that same spot.. usually the stem is a good marker

    #2 the wheel isn't square in the bike. Can't tell you how many time I work on bikes with complaints of things being "out", brakes rubbing, chain skipping.. bla bla bla.. and it's just the wheel wasn't clamped straight. when clamping the wheel in place with a quick release make sure the bike is on the ground,.. not in the stand. lean over the seat or apply a good amount of weight to the rear before clamping the quick release. When you use the QR in the stand the action of the lever clamping down will always twist the wheel in the frame

    also remember after straightening that you have to re-adjust the shifters/cable and possibly the stops if you've played with them trying the adjust t the bent/out setup.
    Last edited by thomllama; 06-25-2013 at 09:12 AM.
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  16. #16
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    Proving that sometimes fancy tools aren't worth the price of admission

    Glad you got it fixed !!!
    Thomllama is right, readjust everything.

    Also,
    Sell the extra derailleur to compensate for the tool cost + Keep an eye on the alignment.
    Once something like this bends, it has been weakened, and might bend again from hard pedaling/shifting.
    If it does, your next step should be to replace the hanger.

  17. #17
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    Quote Originally Posted by johnb View Post
    So.... the moral of the story is: I could have done this with a rusty old crescent wrench.
    Yep. I use a crescent wrench and eyeball it. Sometimes I just use my hands and grab the derailleur, bending the hanger until it's straight. I've done this for over 10 years and it has never failed to work.

    A lot of people insist you buy the specialty tools like a derailleur alignment gauge or a real headset press, but I've found they are more for convenience and protocol but are rarely necessary.

  18. #18
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    Quote Originally Posted by jtmartino View Post
    Yep. I use a crescent wrench and eyeball it. Sometimes I just use my hands and grab the derailleur, bending the hanger until it's straight. I've done this for over 10 years and it has never failed to work.

    A lot of people insist you buy the specialty tools like a derailleur alignment gauge or a real headset press, but I've found they are more for convenience and protocol but are rarely necessary.
    chain & cassette will wear 2x faster it you don't use the tool... you may get it looking good vertically but you'll never be able to eyeball it horizontally and the jockey wheels being twisted out to the cassette will wear things out much faster... it'll shift Ok-ish most of the time.. but not a good thing.
    Last edited by thomllama; 06-26-2013 at 02:59 AM.
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  19. #19
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    Quote Originally Posted by thomllama View Post
    chain & cassette will wear 2x faster it yo do't use the tool... you may get it looking good vertically but you'll never be able to eyeball it horizontally and the jockey wheels being twisted out to the cassette will wear things out much faster... it'll shift Ok-ish most of the time.. but not a good thing.
    2x faster? Did you just make that up?

    I used to pay very close attention to my drivetrain wear because I used Ti XTR 8-speed cassettes. Hard to find, very expensive. I've never, ever had a problem with my derailleur hanger that had to be fixed by an alignment gauge. Hell, I don't think I've ever used a gauge on any of my bikes except for back when I worked in a shop. Most of my bikes back then were steel hardtails without removable hangers.

    Anyone with reasonable vision and basic mechanical ability can eyeball the alignment. You do not need a tool, as supported by the OP's statement. I mean, maybe YOU need the tool thomllama, but I don't, and I don't recommend other people to jump up and buy one the minute they have a problem. You can eyeball both the vertical and horizontal alignment. That's how you have to fix bent derailleur cages for when the hanger isn't the problem.

    My bikes shift great and I don't use an alignment gauge. Do what works for you, and don't buy expensive tools just because someone told you to. Same logic goes for the whole Park vs. Non-Park brand stuff - sometimes the cheap stuff works just fine for 99% of users.

  20. #20
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    Quote Originally Posted by jtmartino View Post
    2x faster? Did you just make that up?

    I used to pay very close attention to my drivetrain wear because I used Ti XTR 8-speed cassettes. Hard to find, very expensive. I've never, ever had a problem with my derailleur hanger that had to be fixed by an alignment gauge. Hell, I don't think I've ever used a gauge on any of my bikes except for back when I worked in a shop. Most of my bikes back then were steel hardtails without removable hangers.

    Anyone with reasonable vision and basic mechanical ability can eyeball the alignment. You do not need a tool, as supported by the OP's statement. I mean, maybe YOU need the tool thomllama, but I don't, and I don't recommend other people to jump up and buy one the minute they have a problem. You can eyeball both the vertical and horizontal alignment. That's how you have to fix bent derailleur cages for when the hanger isn't the problem.

    My bikes shift great and I don't use an alignment gauge. Do what works for you, and don't buy expensive tools just because someone told you to. Same logic goes for the whole Park vs. Non-Park brand stuff - sometimes the cheap stuff works just fine for 99% of users.
    well if it works for you.. great... but I've fixed at least 8 or 9 ghost shifts this yr already that the hanger and derailleur look fine by eye.. but was tweaked enough to cause the chain jump, ghost shift effect.. Everyone plays with cable tension and stops but if the derailleur hanger is out front to back it'll likely skip on ya and possible drop the chain down between the spokes and cassette or just give rough shifting and/or wear the drive train...
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  21. #21
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    I was reading some of the followup replies and felt that I should followup with some information of my own... so maybe saga isn't over, or at least not with myself... maybe this thread should be

    I was going to write this in my last post, but I was pressed for time that night. After I eyeballed the hanger straight, I did have to adjust the derailleur. And it took longer than usual. In fact I never got it perfect, but it was getting late, and I was planning to ride the next day, so I called it close enough. What I couldn't get right was the indexing / cable tension. Yup, a little ghost shifting. And last night when I rode it did that.

    The other night when I was using the hanger tool, I did think about the wheel being out of true, or mounted in the frame cock-eyed, as part of the problem. But both of those checked out. The wheel is slightly out of true. "Maybe" a sixteenth of an inch. But either way, I had planned on trying that again - using the tool the proper way.

    Maybe I'll fiddle with it this weekend (high chance of rain). I need to try to get the indexing right first. If it still ghost shifts, then maybe there is my answer.

    I'm going to hang on to the spare (original) hanger. About 5 years ago, with a different bike, I broke the hanger while out riding. I had a brand new pair of very stiff Sidi shoes on. And I didn't have a chain brake with me. So I had to walk over 3 miles back to the trailhead. Not fun. My feet felt like they'd been run over by a truck. After that I immediately went out and bought a spare hanger and started carrying it in my Camelbak. And that's where the spare will stay for this bike. It's very rare to break one of those on a ride, but it sucks when you do

    As far as the hanger adjustment tool... I just need to give it more time. And work with it when I have plenty of time.

  22. #22
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    It is possible for the hanger to be dead on straight and have a derailleur that is still not aligned properly. Derailleurs can get tweaked too

  23. #23
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    Quote Originally Posted by J.B. Weld View Post
    It is possible for the hanger to be dead on straight and have a derailleur that is still not aligned properly. Derailleurs can get tweaked too
    true enough!
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  24. #24
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    The tool is really useful and it will get the hanger straight with the cassette. If it's still crooked, it means that the derailleur hanger is not the culprit but the derailleur itself. I used to have a couple of derailleurs do the same thing; no amount of straightening of the hanger would get them aligned with the cassette. After replacing the derailleur, it was all good.

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