Weird problem here...- Mtbr.com
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  1. #1
    nocturnal oblivion
    Reputation: stumblemumble's Avatar
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    Weird problem here...

    Just converted my Niner SIR to SS using a Wheels Manufacturing cogset and my very new Race Face ramped ring.
    Problem: The chain tension and loosens with crank rotation. My only guess is that the RF ring is slightly oval/eccentric. It's just enough of a change to be an issue. At the loose end the chain is slightly too loose, then slightly to tight at the other end of rotation.

    Am I missing something?

  2. #2
    mtbr member
    Reputation: Andy R's Avatar
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    As you surmised, the chainring isn't running true - slacken off the chainring bolts and then re-nip them just enough to hold the chainring firmly in place but still allowing it to be moved on the little clearance it will have.

    Rotate the cranks until you find the tightest spot and then give the chainring a tap backwards (with a block of wood or soft hammer). Check to see if there's any improvement and, if neccessary, repeat the process until you get the best possible result. Then fully tighten the bolts.

    If this doesn't do the trick try rotating the chainring 180 degrees on the spider to see if that makes a difference - if you can't make any improvements this way then bite the bullet and get a dedicated SS chainring. Concentricity isn't really a big issue with geared rings as the rear mech takes up any minor differences in tension - most SS chainrings are a big improvement in this respect (and they have proper full-depth teeth too).

    Here you go....

  3. #3
    nocturnal oblivion
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    I figured Race Face rings to be machined and wouldn't have that imperfection. Thanks for the link, that's what I'll be getting. The ring is definitely oblong BTW.

  4. #4
    mtbr member
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    I have the same problem on my Monocog,

  5. #5
    Schipperkes are cool.
    Reputation: banks's Avatar
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    It can also be related to the crank arm, the bottom bracket, the rear cog, the freehub body, the freewheel, rear hub axle.
    Quote Originally Posted by mikesee
    Better suited to non-aggressive 125# gals named Russell.
    I ride so slow, your Garmin will shut off.

  6. #6
    mtbr member
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    Perfectly normal for this too happen.
    I have never seen a chain ring that is perfectly round

  7. #7
    ridin' Mary
    Reputation: OhNooo's Avatar
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    Check the fit on your chainring bolts. I found that one set was really sloppy on my SS chainring, so I swapped out with another brand of chainring bolt that is a super tight fit. This prevents user error during tightening.

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