Frame crack = gear slippage?- Mtbr.com
Results 1 to 5 of 5
  1. #1
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    5

    Frame crack = gear slippage?

    Hi all!

    Too bad my first post is about a problem - I'm riding an old Al hardtail converted over to SS with a Paul singulator thingy. I rode yesterday without probs, then today I switch over to a 32:18 setup (from 32:16 - I'm old and weak!). Suddenly today I was experiencing severe slipping/skipping at the rear cog/singulator on hard, out of saddle efforts.

    Now, the chain-line is bang on, and I'm 99% certain this is not a worn chain, stiff link, worn cog, or worn chainring issue (the 16T cog was brand new and did not slip - the 18T is also new). While cruising the drivetrain is smooth, and backpedaling produces no jumps or skips.

    So after f**ing around with my wheel and the cog for an hour or so, I notice a little area of chipped paint on the bottom of the drive side chainstay. Cleaned it off and it looks like a tiny crack (maybe 1/2 a dime diameter in length?). Hard to tell though due to some discoloration and because it's so small. Sorry no photo - digitally challenged.

    So the long and short (more long, I suppose) of my question is this - could a crack that small in the chainstay cause such bad gear skipping during hard efforts? If I am halluncinating and there is no crack, what have I missed? Any thoughts are very much appreciated.

    Thanks!
    -Chubby

  2. #2
    Pit Bull lover
    Reputation: AaronJ's Avatar
    Join Date
    Apr 2006
    Posts
    72

    ?

    if you are using a bmx or one speed specific chain (1/2" x 1/8"), your front chainring and rear cog should both be 1/8"

    if you are using a multispeed chain (8 speed and under) (1/2" x 3/32") your front chainring and rear cog should both be 3/32".

    check the chainring and cog. it should be etched on there somewhere whether they're 1/8" or 3/32".

    sounds to me like one of the pieces may not match up with the others, which is causing your problem.

    if someone sees something incorrect about what i've just said, please set me straight.

  3. #3
    Nouveau Retrogrouch SuperModerator
    Reputation: shiggy's Avatar
    Join Date
    Dec 1998
    Posts
    48,236
    Quote Originally Posted by AaronJ
    if you are using a bmx or one speed specific chain (1/2" x 1/8"), your front chainring and rear cog should both be 1/8"

    if you are using a multispeed chain (8 speed and under) (1/2" x 3/32") your front chainring and rear cog should both be 3/32".

    check the chainring and cog. it should be etched on there somewhere whether they're 1/8" or 3/32".

    sounds to me like one of the pieces may not match up with the others, which is causing your problem.

    if someone sees something incorrect about what i've just said, please set me straight.
    1/8" chains work just fine on 3/32" cogs and rings. I have been doing it for 7 years on three different bikes without a single issue.

    Only the widths are different. The pitch is the same.
    mtbtires.com
    The trouble with common sense is it is no longer common

  4. #4
    Nouveau Retrogrouch SuperModerator
    Reputation: shiggy's Avatar
    Join Date
    Dec 1998
    Posts
    48,236
    Quote Originally Posted by ChubbyBiker
    Hi all!

    Too bad my first post is about a problem - I'm riding an old Al hardtail converted over to SS with a Paul singulator thingy. I rode yesterday without probs, then today I switch over to a 32:18 setup (from 32:16 - I'm old and weak!). Suddenly today I was experiencing severe slipping/skipping at the rear cog/singulator on hard, out of saddle efforts.

    Now, the chain-line is bang on, and I'm 99% certain this is not a worn chain, stiff link, worn cog, or worn chainring issue (the 16T cog was brand new and did not slip - the 18T is also new). While cruising the drivetrain is smooth, and backpedaling produces no jumps or skips.

    So after f**ing around with my wheel and the cog for an hour or so, I notice a little area of chipped paint on the bottom of the drive side chainstay. Cleaned it off and it looks like a tiny crack (maybe 1/2 a dime diameter in length?). Hard to tell though due to some discoloration and because it's so small. Sorry no photo - digitally challenged.

    So the long and short (more long, I suppose) of my question is this - could a crack that small in the chainstay cause such bad gear skipping during hard efforts? If I am halluncinating and there is no crack, what have I missed? Any thoughts are very much appreciated.

    Thanks!
    -Chubby
    Unless the stay is completely broken through I doubt if it is causing the skipping.
    mtbtires.com
    The trouble with common sense is it is no longer common

  5. #5
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    5
    Thanks for the thoughts. Upon closer inspection, it doesn't appear to be a crack after all - just a weird, tiered chip in the paint. But the skipping remains...

    The chainring says only says 9 speed on it, so I assume it's 3/32 (no ramps or pins though, hmmm). The cog is definitely 3/32 (stamped right on there). The chain itself, I **think** is a multispeed chain, so it should be kosher, too. In any case, per Shiggy it seems it shouldn't matter?

    But, the previous 16T cog was a Shimano BMX cog (probably 1/8, no stamping to confirm). I also ran this same chainring with a 14T Shimano BMX cog for a long time without problems (different chain, though I think that one was also multispeed). Sure feels like worn gears and/or a stretched chain when it slips, though, which would be more in line with AaronJ's comment... Maybe a trip to the LBS is in order.

Members who have read this thread: 0

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2019 VerticalScope Inc. All rights reserved.