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  1. #1
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    "Reading" a Chainring - is it the culprit

    The the drivetrain just doesn't feel right... it's hard to pin down/describe. It may be in my head. But, it feels like it's dragging and just not as smooth as it should be. I may (?) have found the culprit.

    Components:
    - Dura-Ace crank/chainring; 4 yrs, 15,000 miles
    - 6800 bottom bracket; 1+ yrs, 6,000 miles
    - 6800 cassette; 1+ yrs, 6,000 miles
    - 6800 derailleurs; 1+ yrs, 6,000 miles
    - Ultegra chain; 1,000 miles
    - Dura-Ace C24 wheels or Cannondale Hollowgram Si wheels (DT Swiss hubs)... swapping the wheels doesn't change the vague feel I'm chasing. Plus the Cannondale wheels are a week old.

    The bike/drivetrain is kept very clean, always lubed, rarely (intentionally) ridden in the rain.

    There is zero slippage even under hard sprints, but I'm still wondering if the large chainring is the source. I know the chainring is worn... but is it toast, e.g. beyond time to replace? And, other than slipping, what are the symptoms (if any) of a worn chainring?

    Thanks!

    "Reading" a Chainring - is it the culprit-screen-shot-2017-08-28-8.34.15-am.jpg
    Last edited by OldZaskar; 08-28-2017 at 04:35 AM.

  2. #2
    hfc
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    That looks very worn to me. Kind of surprising though as a ring should last more than 15k miles.

  3. #3
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    Thanks hfc. Admittedly, the 15,000 is a guesstimate. It could be closer to 18,000... more of a "Okay, got the pm in 2014... I think it was spring... I average 5,000 miles/yr..."

  4. #4
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    Symptoms of a worn chainring can include chainsuck when shifting from the large to the small chainring because the shape of the worn teeth won't let go of the chain during the downshift.

    It can also include overshipped chains during upshifts as the worn teeth don't engage the chain properly.

    Is it possible you installed the large chainring with improper orientation with regard to the small ring and the crankarm? There's usually an indicator mark on the outside of the ring indicating proper orientation.

    At the absolute worst, you buy a new chainring and it doesn't work. So you put the original chainring back on and save the new chainring for future use. You won't have wasted any money either way.

  5. #5
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    Thanks Peter. I'm not getting any of the classic worn chainring symptoms - slipping, poor shifting, chain suck, etc. But, I did just remember one of the simple tests - pull the chain, see how far off the teeth it goes. Yeah... FAIL. Time for new chainring. So, you're - start there. Even if that's not what I'm feeling, I know I need a chainring.

    "Reading" a Chainring - is it the culprit-screen-shot-2017-08-28-8.34.01-am.jpg]
    Last edited by OldZaskar; 08-28-2017 at 04:35 AM.

  6. #6
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    A related question... Any reason not to use a 6750 50t 110mm to replace the worn 7900 chainring? Current chainring is a 50t 110mm

    Thanks!
    Last edited by OldZaskar; 08-28-2017 at 05:08 AM.

  7. #7
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    Quote Originally Posted by hfc View Post
    That looks very worn to me. Kind of surprising though as a ring should last more than 15k miles.

    Unless you are in the large ring most of the time. Add to that you have a newer chain which won't mesh up properly with older rings and cogs.
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  8. #8
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    Yeah - not in the small ring much at all. The cassette is relatively new. I ordered a new chainring and chain. While everything's apart, I'll inspect the derailleur jockey/idler pulleys. That should eliminate any (real or perceived) drag.

  9. #9
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    Quote Originally Posted by OldZaskar View Post
    Yeah - not in the small ring much at all. The cassette is relatively new. I ordered a new chainring and chain. While everything's apart, I'll inspect the derailleur jockey/idler pulleys. That should eliminate any (real or perceived) drag.
    My strategy is to "share the workload" as much as possible. At least try to stay off the largest two cogs when in the big ring. The resultant cross-chaining will grind down the best of rings. Fresh chains go on every 4k.

    Those Dura Ace 7900 or 9000 big rings cost an arm and a leg. Luckily, my stash includes new ones in reserve, after scoring them for cheap. The rings on both my groups got over 15k miles and look good for at least another 10k.

    Never hurts to see how freely the cranks spin with the chain off. Sometimes some grit works its way in there early and causes a premature death. Fortunately, the DA or Ultegra bb's are inexpensive.

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