drive line "knock"- Mtbr.com
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  1. #1
    PSYCHOLUST
    Reputation: scyule's Avatar
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    drive line "knock"

    Hey Guys..... I am hoping someone can shed some light on this for me:
    My Girlfreind just got an SS road boke with a flipflop rear hub and it runs a KMC 510HX chain. While pedaling there is a rythmic "knock knock" with each rotation. I had the same noise on an old Monocog I had a while back. It almost sounded like the chain binding from being too tight, but the tension seems fine....... Anyone out there have an idea on a fix?

    thanks

  2. #2
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    Sounds like a stiff link to me.

  3. #3
    PSYCHOLUST
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    OK, that sounds like a good starting point.... I'll pull the chain and go over it link by link...thanks

  4. #4
    My spoon is too big!
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    My cheapo ACS freewheel makes a similar sound.
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  5. #5
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    I recently had what sounds like the same thing happening on my road bike with a Surly flip flop hub. It was an intermittent knock that would happen ~ 6X per crank revolution (2X per wheel revolution with 48:16 gearing). It has been driving me nuts, but I *think* I nailed it down to a bit of slop in the wheel bearings, which I've since snugged up.

  6. #6
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    +1 on the ACS freewheel

    .........and the knock wasn't consistent. I backpedal and 9 out of 10 times it goes away for a few minutes. I've heard that replacing the freewheel will fix the problem, but I'm going to ride it until it explodes.

  7. #7
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    bdoggie, you may want to take a look at your rear wheel bearings too. My knock also had a tendency to disappear on backpedaling once or twice. I was running a nearly new Shimano freewheel at first. It got worse when I switched over to a moderately used ACS, but I think that was a result of some additional loosening of the bearing that happened when I dis/remounted the wheel. It was the first time removing the wheel and I neglected to check tightness when I first assembled the bike. While slowly rotating the rear wheel (bike upside down on bench) with the pedals while using hand pressure to provide resistance to spinning, I could feel the "clunk". Pushing the wheel side to side finally pointed me to the bearing. Snugging it up eliminated the problem on the bench, but I've not gotten out for a ride of any distance yet to give it a real test.


    A word of advice to anyone purchasing an "assembled" bike from QBP (Surly or Salsa): Meticulously inspect everything for proper tightness or be ready for a surprise while on a ride.

  8. #8
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    My ACS freewheel on my commuter does the same thing as well. It only happens with the freewheel in certain positions though. If I let it freewheel for just a second and start pedaling again, the sound stops.

  9. #9
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    are your chainring and freewheel perfectly round?

  10. #10
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    Quote Originally Posted by ssm-gd3
    are your chainring and freewheel perfectly round?
    on a similar note, has anyone got any tricks for centering a chainring on a 4 bolt 104bcd crankset? My chain gets tight then loose, tight then loose when I rotate the cranks.

  11. #11
    nothing to see here
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    I think the popular method involves loosening all the chainring bolts to the point where they are just tight enough to allow movement of the chainring on the spider. Rotate the crank to the tight spot, then squeeze the chain together, or tap it lightly, to allow the chainring to centre itself. This needs to be repeated a few times at different crank positions to ensure the eccentricity is completely (read: acceptably) eliminated. If this fails to resolve the issue, remove the chainring completely and rotate 180 degrees before mounting again, and then repeat the above procedure.
    I see hills.

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  12. #12
    Nouveau Retrogrouch SuperModerator
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    Quote Originally Posted by JDG1317
    My ACS freewheel on my commuter does the same thing as well. It only happens with the freewheel in certain positions though. If I let it freewheel for just a second and start pedaling again, the sound stops.
    Ahh, yes! The dreaded ACS Claws knock. It will take a while for the FW to blow up even as the noise gets worse.

    The onset of the knock can be delayed greatly by soaking the new, unused FW in synthetic motor oil for a couple of days before installing it (do let it drain first).

    It helps a used, knocking FW, too, but the knock will return in a week or so.

    The permanent fix is getting a White Industries ENO FW.
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  13. #13
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    thanks stevob, I will give that a try.

  14. #14
    Nouveau Retrogrouch SuperModerator
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    Quote Originally Posted by Stevob
    I think the popular method involves loosening all the chainring bolts to the point where they are just tight enough to allow movement of the chainring on the spider. Rotate the crank to the tight spot, then squeeze the chain together, or tap it lightly, to allow the chainring to centre itself. This needs to be repeated a few times at different crank positions to ensure the eccentricity is completely (read: acceptably) eliminated. If this fails to resolve the issue, remove the chainring completely and rotate 180 degrees* before mounting again, and then repeat the above procedure.
    * rotate the ring one position (90) and repeat.
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  15. #15
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    I will second the FW knock. Both shimano and ACS will knock. Once they start to knock I have found that means they have reached their half life and you are on the downward slope to needing a new FW.

    Fix:
    Cassette hub.
    Quote Originally Posted by OneBadWagon
    Since about half of the posts on here are about intangibles or hypotheticals, let's hear it!

  16. #16
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    Happened with my Shimano freewheel as well. It started knocking intermittently, and kicking the pedals back would silence it temporarily. I bought a White freewheel and haven't even thought about it since.

    Ironically, the Shimano freewheel made too much noise so I replaced it with a White, and now it sounds like a swarm of bees constantly chasing me.

  17. #17
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    +1 on FW

    Finally got a rode ride in today after all of the New England rain and confirmed that what I thought was a result of loose bearings (see previous post) is actually the freewheel. It was happening on a brand new Shimano (<100 mi) and is slightly worse on the used ACS that replaced it. Damn.

    So now I gotta buy a White or get a new wheel with freehub/cog, eh? I now my options with White ($ or $$ ), anyone have recommendations for a road worthy 135 mm spaced rear hub?

  18. #18
    is buachail foighneach me
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    It is undoubtedly the freewheel. Only one I've had that doesn't do it is White Industries. Freehub or WI freewheel. The only ways to get rid of it are to buy a better product.

  19. #19
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    Quote Originally Posted by magnetosphere
    Once they start to knock I have found that means they have reached their half life and you are on the downward slope to needing a new FW.
    thats ****ing funny. my cheap ass freewheel just started making noise.........you always get what you paid for.

  20. #20
    PSYCHOLUST
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    Well, Thanks again everyone....... I'm going to order a White Industries FW....

    I'm sure the one that is on there has YEARS of working perfectly well left in it, noises drive me CRAZY!!!!!

    THANKS!!!!!

  21. #21
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    ENO is the answer

    I've had the same problem, in fact, everyone has had the same problem. Everyone that has used a freewheel other than a White Industries Eno. All other freewheels knock and are not
    concentric. Eno's are expensive but worth the expense. This is the only way to eliminate single speed drive train knock. Been there..........done that.

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