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  1. #1
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    Indescribable problem with the drivetrain

    Hey, lately I have come across a rather frustrating problem with my specialized hardrock. The problem is that occasionally after riding my local mountain my rear derailleur starts to flick forward and bouncing the chain, this usually stops the ability to pedal until until the derailleur moves back. I need to know what the problem is ASAP because I'm due out again in a few days. I have no idea if it's a problem with the rear derailleur or rear cassette or maybe just a large mud build up somewhere unseen (I usually stop when this happens to check for clumps of mud but never find any obstructing anything)

    Thanks for any Input, Darcy.

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  2. #2
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    how old is your bike? it sounds like "chain suck" to me. that means your chainring and/or chain are worn out. you will need to have your LBS check it out to see how far worn the chain and rings are.

  3. #3
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    It's only 3 months old but I have done about 1000 miles on it, I thought that may be the problem but wanted to check here first incase I was wrong and played 50 quid for my LBS service. Also could using dry lube in the wet be a contributing factor to the problem? Thanks for the quick reply Mack .

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  4. #4
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    Sorry for double post but this also happened to me within the first week of owning the bike.

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  5. #5
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    i could be a lot of things that will be difficult to discern without seeing the bike in person. maybe the chain is rusty, maybe you bent a tooth on a chainring. perhaps the chain is a broken link or a "tight spot."

  6. #6
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    Does it happen only when under power, or when coasting too? Is limited to any particular gear combinations?

    And as mentioned above, definitely give the chain and rings good a looking over. You've put some miles on them; if you're riding in wet and dirty conditions, you could have some decent wear going on.
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  7. #7
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    Make sure your front derailluer is adjusted correctly and not rubbing..

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  8. #8
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    If the bike had a lot of miles on it and it only happened in one of the chainrings (OP didn't specify), I would suspect a worn chainring, but I don't think there are that many miles on the bike to have caused that, especially if the chainrings are steel.

    First thing I would look for would be for a stiff link in the chain.

    Or if that is not the case, possibly one of the jockey wheels on the rear derailleur not rolling smoothly.

  9. #9
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    I suspect chain suck is the culprit. I encountered this early on whenever I failed to adequately lube my chain, or soon after a ride in the rain or wet conditions, after the chain sat for a day or so, wet, and with a lack of oil. Here in Hawaii I learned quickly that I needed to wipe off and lubricate my chain before every ride...no more chain suck!

  10. #10
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    I used to get this on my old bike only when coasting. Turned out the crunching noise was the paws being ground up in my hub. I had to get a new hub. If you are getting chain suck when coasting I would make sure the area around the casset is clean and free of debris. As in mud and grass wrapped around the axel. You could solve this hole thing by going single speed.

  11. #11
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    UK winter? I'm with those who are guessing chain suck. Clean your drivetrain a bit better before lubricating and try a heavier, wet lube. Also if you're cross-chaining, don't.
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  12. #12
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    The free hub might need to be servised.

  13. #13
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    Could be chain suck but he doesn't say the chain is sucked up in the frame just the rear derailleur is flicking forward which sounds to me more like a dirty freewheel/hub or even the rear cogs on the derailleur could be really caked in crap. I know everyone cleans there chain and cassette but a lot forget those little cogs which get really gummed up quickly.
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  14. #14
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    I'm going to go check my hubs and rear cassette now for any build ups of dirt, grit and grime, clean them and apply some wet lube I got earlier. I'm riding tomorrow so I will post back if it made any help.
    Thank you everybody for your input.

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  15. #15
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    I'm not sure how pedaling is affected by the derailleur flicking forward (more specificity would be good).

    I'd try a step by step diagnostic (isolating the components one at a time until you find the culprit). I'd probably start with the cassette and freehub (looking for damage, binding of the freehub, etc.) then look at the chain for binding, twisting or wear and I'd pull the pulleys and re-lube them checking for damage while they're off. Finally, ensure your derailleur is pivoting freely and not binding during operation. I've had stuff as simple as a tight chain link or a small rock in the chain cause these types of symptoms, other times it was harder to find.

  16. #16
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    Quote Originally Posted by Forster View Post
    I'm not sure how pedaling is affected by the derailleur flicking forward (more specificity would be good).
    I re-read the OP, and still suspect chainsuck, likely caused by tight/frozen chain links. As these tight links exit the chain ring, they retain the shape of the ring and fail to straighten out and head towards the derailleur right away. This in turn pulls the derailleur forward. The tight links continue to travel upward around the chain ring until enough pressure is placed on the chain to overcome the binding link(s) and the chain suddenly straightens out again allowing the derailleur to return to normal position rapidly - all of this causing the "flicking" of the D. If severe enough, the chain will actually continue traveling upward as it exits the chain ring until pedaling forward is no longer possible. This is how tight/poorly lubed chain links can negatively affect both rear derailleur action AND pedaling.

  17. #17
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    Take it to a shop and have a mechanic go over it, showing you what the problem is, and how to avoid it in the future. Lube choice is definitely going to affect the quality of your ride, though whether it is the main cause of your problems is hard to say. Dry lube is pretty much useless in the wet after a few miles because it's supposed to fall off to keep dust/grit out of your drivetrain. I switched to a wet lube on my bikes months ago.

    Also possible after 1,000mi is some wear that will at least necessitate some adjustments. Possibly enough to require some new parts. Riding in the wet increases wear on parts, especially if there is grit in there (you can usually hear it grinding away when you're pedaling if it's there) and also when you start getting some surface rust (rust is abrasive and will help grind down your drivetrain).

    Do you ride in freezing temps much? Lube selection makes a difference here, too. Some lubes freeze in the cold, which plays havoc on bike parts. I've seen shifters and freehubs become useless because the lube inside froze. They work fine once they warm up again. Getting that fixed requires cleaning the old, gummy lube out, and using something that will hold up to cold temps. I've had good luck so far with Phil Wood's Tenacious Oil in both shifters and freehubs (it quiets noisy freehubs, too). It's more viscous than what you usually find in there, but it hasn't frozen on me yet.

    I'd like a concise definition of chainsuck. The way I see it used by people is to describe a fairly wide variety of problems with the chain, to the point that it is no longer descriptive of much of anything.

  18. #18
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    For me, chainsuck is when the chain stays on a chainring or cog after the point where it should exit. If it's bad enough, it can loop around a chainring to where it tucks under the part of the chain that's under tension. At that point, it's pretty easy to rip the rear derailleur off. Totally lame.
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