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  1. #1
    Join Date
    Apr 2009
    Location
    Tucson, AZ
    Posts
    4,632

    Warped chainring.

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    I fell over the last time I took my bike out, and in getting my bike ready for a trip back home tonight, noticed the "kerchunk" noise. (Fiddling with my bike is more fun than studying for a biology final.) It appears that the big chainring is bent slightly. The teeth are all fine, and the weird bit is that it's rubbing the outside of the derailleur cage, rather than the inside, where I'd expect it to if I fell to the right (as always seems to happen). It's also much more noticeable if I turn the pedals backward, which is also slightly odd. I'm taking it to the bike shop when I get home, as it needs a tuneup anyway. I've got a few questions:
    1) While I know it's theoretically fixable according to my Book of Bike Maintenance (made up title), is it actually fixable, and would it count as a "major tuneup?"
    2) If it isn't fixable, how much can I expect to pay for a relatively entry-level 52-tooth chainring? Less than $100, I know, as my google-fu has only really turned up prices for Dura-Ace.
    Thanks in advance!
    Last edited by Owlie; 12-13-2009 at 04:49 PM. Reason: I occasionally can't punctuate sentences.
    At least I don't leave slime trails.
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  2. #2
    Join Date
    Jul 2006
    Location
    Olney, MD
    Posts
    3,063
    Repairing a chain ring may not be included in a tuneup, major or minor. If it can be bent back I wouldn't think it would take much time or cost much.

    I think you can get a 105-level chain ring for around $30.
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  3. #3
    Join Date
    Sep 2007
    Location
    Uncanny Valley
    Posts
    14,498
    If the rub is directly opposite the crankarm, I'd worry that you might have bent the bottom bracket spindle, or dislodged the crank?

    I would definitely let your LBS look at it. As for prices, $30 looks more like the price for a 39T middle chainring (I'm not having any trouble finding them on Google ). Looks like 105-level 50-52T rings are more in the $50 range.
    Speed comes from what you put behind you. - Judi Ketteler

  4. #4
    Join Date
    Apr 2009
    Location
    Tucson, AZ
    Posts
    4,632
    After a bit of moving the pedals around, it's still rubbing, but not making the "kerchunk" noise. It's only rubbing between the two bolts on either side of the crank arm.
    Would a bent bottom-bracket spindle or dislodged crank impact the "feel" of moving the pedal? Apart from the rubbing, it's no different from usual, and it's only rubbing in the big ring (I would think it would impact the other rings, but I could be wrong.)

    As for the Google, I'm not trying very hard...there's a bio final between me and the bike shop!
    Last edited by Owlie; 12-13-2009 at 09:02 PM.
    At least I don't leave slime trails.
    http://wholecog.wordpress.com/

    2009 Giant Avail 3 |Specialized Jett 143

    2013 Charge Filter Apex| Specialized Jett 143
    1996(?) Giant Iguana 630|Specialized Riva


    Saving for the next one...

  5. #5
    Join Date
    Apr 2006
    Location
    Maine
    Posts
    959

    Warped chainring

    It's hard for me to believe that you would have bent the bottom bracket, although certainly not impossible. The other option here is that the chainring bolts could be loose, or perhaps you lost one? All of this would lead to bending the chainring. At any rate, I'm sure that your LBS will figure out everything for you.

    Good luck with your final!

 

 

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