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Thread: Chain tightness/noise

  1. #1
    Hipster
    Join Date
    Apr 2006
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    38

    Chain tightness/noise

    I have just finished my first fixie conversion and have a question or two on chain noise.

    I am running a 3/32 drive train with a 1/8 (temporary) chain. The chain line is within a millimeter or so of being straight. I have tightened the chain so that the cranks spin without catching but there is minimal droop in the chain between cassette and sprockets.

    While riding there is a little bit of general noise in the drivetrain which I expected with the different size chain.

    The problem I noticed is when going downhill at very high crank rpms (150 ish). Everything is fine untill I hit the point where my legs are just keeping up with the cranks and the chain is essentially slack. When I hit a bump like this, I suddenly get a rather large grinding noise from the drivetrain. This scared the crap out of me the first time, as I though I had thrown the chain and was about to get personal with the pavement. When I stopped and checked the bike the chain tension all looked fine and there seems like there is nowhere near enough slack to throw it off.

    My questions basically are: Is this sort of thing normal and anything to worry about? Is +/- 1mm an accurate enough chainline to prevent throwing the chain? Should the chain be as tight as physically possible before it interferes with the chainring turning or just tight enough so the chain cannot come off?

    I have really enjoyed the first few rides on the fixie and will join one of the brisbane rides soon.

  2. #2
    Moderator
    Join Date
    Nov 2005
    Posts
    1,039

    Chain tightness/noise

    how tight your chain is depends on how round your ring is.

    On my 1st conversion, the chainring I was using was not perfectly round so I had to have extra slack on the chain to compensate for the "tight" spot.

    You're basically right, the chain should be as tight as possible without interfering with the spinning of the cranks. Good way to check is to pick the bike off the ground and spin the cranks. Let go of the cranks and watch them spin. They should spin freely for a reasonable amount of time.

    Using mis-matched drive parts and an off chainline will result in some noise. But I'm not familiar with the grinding noise you describe when riding fast. Have you checked the teeth in your chainring? Maybe it's as simple as a small stone flew into your drive briefly? That has happened to me before and caused some temporary grinding.

    Des
    No. I do not ride for fashion and I do not care if your bicycle is prettier than mine.

  3. #3
    Hipster
    Join Date
    Apr 2006
    Posts
    38

    Chain tightness/noise

    I don't think it is road junk, like a rock, as it has happend a couple of times now and it is always when the chain is untensioned and I hit a bump.

    I will try and tighten the chain up as much as possible (without jamming) before I commute home today and see if it makes any difference, though it does seem fairly tight already.

  4. #4
    ndf
    Guest

    Chain tightness/noise

    Hey, if you sort out the grinding noise, come along on the Friday night ride - check the other topic for details:

    http://fixed.org.au/forums/viewtopic.php?t=186

    :)

  5. #5
    NJS Certified
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    Nov 2005
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    1,064

    Chain tightness/noise

    Inane.....turn up on Friday night, and we will gladly sort out the issue. I usually find that if I hear an awful noise coming from my bike, a few clicks on my i-pod and they go away.......for a while.

  6. #6
    Hipster
    Join Date
    Apr 2006
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    38

    Chain tightness/noise

    I think I have fixed my problems.

    I must of stuffed up with some part of my build as my chainline was actually 3mm or so out. I am sure I checked it when I finally finished my conversion but it was definately out when I checked again.

    I have used an old chainring as a temporary spacer and though it looks very odd it has fixed the chainline and removed most of the noise. I will have to find a better solution when I have some time.

    I will be away on friday Rhino or I would turn up and show off my bike, even with its double front chainring

  7. #7
    NJS Certified
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    Chain tightness/noise

    No-one will 'poo-poo' you due to your double chainring.....if they do, we will send in the heavies!!!

    PS: Blakey, we nominated you as our resident 'heavy'!!!

  8. #8
    bleep bloop bleep AL9000's Avatar
    Join Date
    Dec 2005
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    14,845

    Chain tightness/noise

    I wouldn't worry about throwing the chain. If you can't push it off the ring with your fingers whilst the wheel is spinning (SLOWLY!), then it's going to take a lot to derail it.

    My chainline's off by 1-2mm, and I've never had an issue.

    Quote Originally Posted by Rhino
    No-one will 'poo-poo' you due to your double chainring.....if they do, we will send in the heavies!!!

    PS: Blakey, we nominated you as our resident 'heavy'!!!
    Sweet, where do I get a hook up for the 'roids then?

  9. #9
    Muppet
    Join Date
    Feb 2006
    Posts
    14

    Chain tightness/noise

    Even if the chain does come off occaisonaly it's not to bad, usually locks up the back wheel first, hell I was flying down Brunwsick st one night, chain skipped and skidded for about 15m and I shit you not, the smell of burning rubber filled the air. Passer bys were a bit confused. Anyway, I have been running a 16t cog and unbeknownst to me I am missing four teeth and it still works fine. Talk about a townie..
    One should never have to choose between your girl and your bike!

  10. #10
    NJS Certified
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    Chain tightness/noise

    Quote Originally Posted by angus
    the smell of burning rubber filled the air.
    I know that all too well.

    I was hooking down swanston street recently when my chain came off. Unfortunately it slipped to the inside of the cog.

    Locked the back wheel up....Skidded across the Lonsdale Street intersection burning rubber.

    But the interesting bit is I ripped out the ends of 4 spokes.

    Good job I did on it. All fixed now though.

    So be careful. If your chains gonna come off, I think it needs to come off to the outside!!!
    'there's very few cars at 0530.....'

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