Chain skipping under load(for no obvious reason)

Discussion in 'Cycling Equipment' started by dabac, Mar 31, 2008.

  1. dabac

    dabac Well-Known Member

    Joined:
    Sep 16, 2003
    Messages:
    2,274
    Likes Received:
    138
    Hi guys,
    I built up a wheel around an old Sachs hub this winter. The cassette had been used before, but still looked good with no obvious changes in tooth shape. Anyhow, since this one is from way before shifting ramps and all that I figured I'd flip the sprockets over to be really certain that it would work well with the new chain I was putting on.
    Well, it isn't. In the stand it runs as smooth as you'd ever wish for, but when I try riding it I get skipping on both smallest AND largest sprocket, and I just can't figure out why.

    Teeth definitely appear symmetrical, the flipped-over side hasn't been run before, there are no stiff links in the chain, I'm not cross-chaining, so what's wrong with it?

    Could a faulty chain length affect BOTH smallest and largets cog performance while leaving the middle unaffected?

    Can worn tension and jockey pulleys have anything to do with it?
     
    Tags:


  2. Jay Beattie

    Jay Beattie Guest

    On Mar 31, 3:04 am, dabac <[email protected]
    mx.forums.cyclingforums.com> wrote:
    > Hi guys,
    > I built up a wheel around an old Sachs hub this winter. The cassette
    > had been used before, but still looked good with no obvious changes in
    > tooth shape. Anyhow, since this one is from way before shifting ramps
    > and all that I figured I'd flip the sprockets over to be really certain
    > that it would work well with the new chain I was putting on.
    > Well, it isn't. In the stand it runs as smooth as you'd ever wish for,
    > but when I try riding it I get skipping on both smallest AND largest
    > sprocket, and I just can't figure out why.
    >
    > Teeth definitely appear symmetrical, the flipped-over side hasn't been
    > run before, there are no stiff links in the chain, I'm not
    > cross-chaining, so what's wrong with it?
    >
    > Could a faulty chain length affect BOTH smallest and largets cog
    > performance while leaving the middle unaffected?
    >
    > Can worn tension and jockey pulleys have anything to do with it?


    Sounds weird, but make sure your cable guide under the BB is well
    greased. Sometimes cable sticking can give you a problem that seems
    like a bad cog/chain combo. Other problems may be: (1) bent
    derailleur hanger, (2) bad derailleur (unlikely), (3) unseen stiff
    link, (4) unseen wear on cogs, and (5) bad juju. Make sure you did
    not sin in a past life. I doubt it is a pulley issue. That would
    would not cause skipping, IMO. -- Jay Beattie.
     
  3. Jay Beattie wrote:

    > Sounds weird, but make sure your cable guide under the BB is
    > well greased. Sometimes cable sticking can give you a problem
    > that seems like a bad cog/chain combo. Other problems may be:
    > (1) bent derailleur hanger, (2) bad derailleur (unlikely), (3)
    > unseen stiff link, (4) unseen wear on cogs, and (5) bad juju.
    > Make sure you did not sin in a past life. I doubt it is a
    > pulley issue. That would would not cause skipping, IMO. --


    Following recent experience with my son's bike, make sure your
    chain doesn't have a twist in it. One link got twisted on his,
    so that the chain tried to derail once every trip over the
    sprocket - but only under load.

    John
     
  4. On Mar 31, 2:26 pm, Jay Beattie <[email protected]> wrote:
    > On Mar 31, 3:04 am, dabac <[email protected]
    >
    >
    >
    >
    >
    > mx.forums.cyclingforums.com> wrote:
    > > Hi guys,
    > > I built up a wheel around an old Sachs hub this winter. The cassette
    > > had been used before, but still looked good with no obvious changes in
    > > tooth shape. Anyhow, since this one is from way before shifting ramps
    > > and all that I figured I'd flip the sprockets over to be really certain
    > > that it would work well with the new chain I was putting on.
    > > Well, it isn't. In the stand it runs as smooth as you'd ever wish for,
    > > but when I try riding it I get skipping on both smallest AND largest
    > > sprocket, and I just can't figure out why.

    >
    > > Teeth definitely appear symmetrical, the flipped-over side hasn't been
    > > run before, there are no stiff links in the chain, I'm not
    > > cross-chaining, so what's wrong with it?

    >
    > > Could a faulty chain length affect BOTH smallest and largets cog
    > > performance while leaving the middle unaffected?

    >
    > > Can worn tension and jockey pulleys have anything to do with it?

    >
    > Sounds weird, but make sure your cable guide under the BB is well
    > greased.  Sometimes cable sticking can give you a problem that seems
    > like a bad cog/chain combo.  Other problems may be: (1) bent
    > derailleur hanger, (2) bad derailleur (unlikely), (3) unseen stiff
    > link, (4) unseen wear on cogs, and (5) bad juju.  Make sure you did
    > not sin in a past life. I doubt it is a pulley issue.  That would
    > would not cause skipping, IMO. -- Jay Beattie.- Hide quoted text -
    >
    > - Show quoted text -


    I had this problem last season for a couple rides of troubleshooting.
    Like Jay says, it was the cable.
     
  5. Leo Lichtman

    Leo Lichtman Guest

    "John Henderson" wrote: (clip) make sure your
    > chain doesn't have a twist in it. (clip)

    ^^^^^^^^^^^^^^^^^
    Moebius chain will do it every time.
     
  6. dabac

    dabac Well-Known Member

    Joined:
    Sep 16, 2003
    Messages:
    2,274
    Likes Received:
    138
    Easy enough, will do.

    But wouldn't that simply cause the RD to hesitate a little when downshifting?
    No 1 is a possibility, the frame has been around for a while too. Nothing immediately visible to the naked eye though.
    Re. no 2 - there is a bit of slop in the RD, but I've seen far worse that still performed better than this.
    I find no 3 highly improbable. Chain was KMC straight out of the box, put together with a quick link. Must have used dozens before, often by pushing the pin back in instead of using a quicklink, never had any trouble.
    If it's no 4 then I'll never trust my eyes again. I swear the tooth flanks on the flipped-over sprockets are pristine.

    LOl, a bit late to think about that by now...

    What's really weird IMO is that it's both smallest and biggest that are affected while the middle ones runs as smooth as you could ever wish. I almost suspect that:
    a) original fit of tooth profile was bad, and got worn to fit by the chain
    b) I missed to flip the middle sprockets over.

    But I can't really see a bike being sold with such a poor fit that it'd require hundreds of miles of break-in riding before the chain would stop skipping.
     
  7. dabac

    dabac Well-Known Member

    Joined:
    Sep 16, 2003
    Messages:
    2,274
    Likes Received:
    138


    I'll look for that too - easy enough. Can't think of it when it'd have happened though. Can't recall any chainsuck or derail incident.
     
  8. dabac

    dabac Well-Known Member

    Joined:
    Sep 16, 2003
    Messages:
    2,274
    Likes Received:
    138
    Thanks for the tips guys, This afternoon I have another 16-mile chance to figure it out...
     
  9. On Mar 31, 4:04 am, dabac <[email protected]
    mx.forums.cyclingforums.com> wrote:
    > Hi guys,
    > I built up a wheel around an old Sachs hub this winter. The cassette
    > had been used before, but still looked good with no obvious changes in
    > tooth shape. Anyhow, since this one is from way before shifting ramps
    > and all that I figured I'd flip the sprockets over to be really certain
    > that it would work well with the new chain I was putting on.
    > Well, it isn't. In the stand it runs as smooth as you'd ever wish for,
    > but when I try riding it I get skipping on both smallest AND largest
    > sprocket, and I just can't figure out why.
    >
    > Teeth definitely appear symmetrical, the flipped-over side hasn't been
    > run before, there are no stiff links in the chain, I'm not
    > cross-chaining, so what's wrong with it?
    >
    > Could a faulty chain length affect BOTH smallest and largets cog
    > performance while leaving the middle unaffected?
    >
    > Can worn tension and jockey pulleys have anything to do with it?
    >
    > --
    > dabac


    Used sprockets don't work with new chains. As in your case, you'll end
    up with a few sprockets that cause the chain to skip. Did you save the
    old chain. If you did, use that one and use it with the cassette until
    both are toast. otherwise, toss the cassette and get a new one.

    To get long life out of a cassette, get two or three chains. clean and
    lube all of them. Use one for a while. Then remove the chain out and
    put the other one on, use it for a while and then switch to the third
    chain. Wash and lube all three. Repeat process. Your chains and
    cassette will work together for several thousand miles.

    Andres
     
  10. dabac

    dabac Well-Known Member

    Joined:
    Sep 16, 2003
    Messages:
    2,274
    Likes Received:
    138
    Did you read the part about me flipping the sprockets over?

    Sheldon's site has that listed as doable. Without sending off to a metallurgy lab I'm as certain I can be that I'm running the new chain on the previously unused sides of the teeth. Not that there was much wear on the other side either.

    Not really an option until I can do a frankenhub conversion and graft a Shimano right flange on to the hub. It's an obsolete Sachs model and new cassettes/sprockets are really hard to find.

    Besides, given the symptoms I'm not so certain that a new Sachs cassette would fix the problem.

    ...unless you're stubborn enough to ride your bike during winters where roads gets sanded and salted...
     
  11. dabac wrote:

    > Sheldon's site has that listed as doable. Without sending off
    > to a metallurgy lab I'm as certain I can be that I'm running
    > the new chain on the previously unused sides of the teeth. Not
    > that there was much wear on the other side either.


    The wear doesn't need to be visible to the eye for a new chain
    to skip. In the past, I've found some chains to be more prone
    to skipping than others. I remember Wippermans circa 1980 as
    being particularly sensitive to any sprocket wear.

    Back then, putting a new Shimano or DID chain on would sometimes
    eliminate the skipping.

    John
     
  12. John Henderson wrote:

    >> Sheldon's site has that listed as doable. Without sending off to a
    >> metallurgy lab I'm as certain I can be that I'm running the new
    >> chain on the previously unused sides of the teeth. Not that there
    >> was much wear on the other side either.


    > The wear doesn't need to be visible to the eye for a new chain to
    > skip. In the past, I've found some chains to be more prone to
    > skipping than others. I remember Wipperman chains circa 1980 as being
    > particularly sensitive to any sprocket wear.


    Visible is probably inaccurate because looking at a chain, one cannot
    readily see the dimension critical to skipping, which is pitch
    elongation. If you hold a ruler next to the chain matching an inch
    mark with the center of a link pin, one foot away the % out of pitch
    is "visible" by the mismatch in twelve inches of chain. 1/8" = 1%.

    > Back then, putting a new Shimano or DID chain on would sometimes
    > eliminate the skipping.


    New chains skip better than worn chains because they do not mesh with
    worn driven sprockets while at the same time they work on worn CWs.

    http://www.sheldonbrown.com/brandt/chain-care.html

    Jobst Brandt
     
  13. [email protected] wrote:

    > John Henderson wrote:
    >
    >>> Sheldon's site has that listed as doable. Without sending
    >>> off to a metallurgy lab I'm as certain I can be that I'm
    >>> running the new
    >>> chain on the previously unused sides of the teeth. Not that
    >>> there was much wear on the other side either.

    >
    >> The wear doesn't need to be visible to the eye for a new
    >> chain to
    >> skip. In the past, I've found some chains to be more prone
    >> to
    >> skipping than others. I remember Wipperman chains circa 1980
    >> as being particularly sensitive to any sprocket wear.

    >
    > Visible is probably inaccurate because looking at a chain, one
    > cannot readily see the dimension critical to skipping, which
    > is pitch
    > elongation. If you hold a ruler next to the chain matching an
    > inch mark with the center of a link pin, one foot away the %
    > out of pitch
    > is "visible" by the mismatch in twelve inches of chain. 1/8"
    > = 1%.
    >
    >> Back then, putting a new Shimano or DID chain on would
    >> sometimes eliminate the skipping.

    >
    > New chains skip better than worn chains because they do not
    > mesh with worn driven sprockets while at the same time they
    > work on worn CWs.
    >
    > http://www.sheldonbrown.com/brandt/chain-care.html


    Yes, and the last time you and I discussed my observation that a
    new brand A chain could skip when a new brand B one didn't, we
    failed to find an explanation.

    John
     
  14. Lou Holtman

    Lou Holtman Guest

    John Henderson wrote:
    > [email protected] wrote:
    >
    >> John Henderson wrote:
    >>
    >>>> Sheldon's site has that listed as doable. Without sending
    >>>> off to a metallurgy lab I'm as certain I can be that I'm
    >>>> running the new
    >>>> chain on the previously unused sides of the teeth. Not that
    >>>> there was much wear on the other side either.
    >>> The wear doesn't need to be visible to the eye for a new
    >>> chain to
    >>> skip. In the past, I've found some chains to be more prone
    >>> to
    >>> skipping than others. I remember Wipperman chains circa 1980
    >>> as being particularly sensitive to any sprocket wear.

    >> Visible is probably inaccurate because looking at a chain, one
    >> cannot readily see the dimension critical to skipping, which
    >> is pitch
    >> elongation. If you hold a ruler next to the chain matching an
    >> inch mark with the center of a link pin, one foot away the %
    >> out of pitch
    >> is "visible" by the mismatch in twelve inches of chain. 1/8"
    >> = 1%.
    >>
    >>> Back then, putting a new Shimano or DID chain on would
    >>> sometimes eliminate the skipping.

    >> New chains skip better than worn chains because they do not
    >> mesh with worn driven sprockets while at the same time they
    >> work on worn CWs.
    >>
    >> http://www.sheldonbrown.com/brandt/chain-care.html

    >
    > Yes, and the last time you and I discussed my observation that a
    > new brand A chain could skip when a new brand B one didn't, we
    > failed to find an explanation.
    >
    > John



    Some chains have more play between the rollers and the sleeves of the
    innerplates. That could be an explanation.

    Lou
     
  15. Jay Beattie

    Jay Beattie Guest

    On Apr 2, 2:19 pm, Lou Holtman <[email protected]> wrote:
    > John Henderson wrote:
    > > [email protected] wrote:

    >
    > >> John Henderson wrote:

    >
    > >>>> Sheldon's site has that listed as doable.  Without sending
    > >>>> off to a metallurgy lab I'm as certain I can be that I'm
    > >>>> running the new
    > >>>> chain on the previously unused sides of the teeth.  Not that
    > >>>> there was much wear on the other side either.
    > >>> The wear doesn't need to be visible to the eye for a new
    > >>> chain to
    > >>> skip.  In the past, I've found some chains to be more prone
    > >>> to
    > >>> skipping than others.  I remember Wipperman chains circa 1980
    > >>> as being particularly sensitive to any sprocket wear.
    > >> Visible is probably inaccurate because looking at a chain, one
    > >> cannot readily see the dimension critical to skipping, which
    > >> is pitch
    > >> elongation.  If you hold a ruler next to the chain matching an
    > >> inch mark with the center of a link pin, one foot away the %
    > >> out of pitch
    > >> is "visible" by the mismatch in twelve inches of chain.  1/8"
    > >> = 1%.

    >
    > >>> Back then, putting a new Shimano or DID chain on would
    > >>> sometimes eliminate the skipping.
    > >> New chains skip better than worn chains because they do not
    > >> mesh with worn driven sprockets while at the same time they
    > >> work on worn CWs.

    >
    > >>http://www.sheldonbrown.com/brandt/chain-care.html

    >
    > > Yes, and the last time you and I discussed my observation that a
    > > new brand A chain could skip when a new brand B one didn't, we
    > > failed to find an explanation.

    >
    > > John

    >
    > Some chains have more play between the rollers and the sleeves of the
    > innerplates. That could be an explanation.


    Although we have been spanked in the past for such statements because
    the relevant distance is pin to pin and not roller to roller (at least
    in terms of wear measurements). -- Jay Beattie.
     
  16. Turning sprockets around to the "unworn side" is a misnomer. Although
    when an elongated chain runs on driven sprockets doing most of its
    wear on the loaded face of teeth, wear also occurs the unloaded face
    because it bears on these as it engages. Inspecting sprocket that has
    been run with a badly worn chain will reveal the backs of teeth as
    shiny and worn.

    Jobst Brandt
     
  17. dabac

    dabac Well-Known Member

    Joined:
    Sep 16, 2003
    Messages:
    2,274
    Likes Received:
    138
    If I put one "reversed" sprocket on top of a "original orientation" sprocket and only line up on two teeth and the valley between them there is no visible shape distorsion at all to my eyes.
    The sprockets have some sort of surface treatment that's slightly grayer than gun black and in a matte finish. When I look on the previously front slopes these have acquired a metallic sheen while the previously rear slopes still has the same lustre as the sides of the sprockets. I maintain that wear is minimal.

    I've gone over the chain again, and it appears fine. No stiff or twisted links. There may be something wrong with the quicklink, it feels a bit too loose sideways, as if it's meant for a wider chain.
    Now, if only there'd been some sense of rhytm to when the chain skipped I'd been quite pleased with that find...
    It also appears as although seemingly symmetrical when viewed from the side the sprockets may not be symmetrical when viewed from the rear, the biggest and smallest appear to have a bevel ground into them, determining their direction of rotation. This might well be a contributing factor to the issues I'm having, although IMO this still doesn't fully explain why it runs so smoothly w/o load and so poorly under load. I'd have imagined seeing at least some skipping or hesitation during the bench runs if this was the cause.
     
  18. dabac wrote:

    > I've gone over the chain again, and it appears fine. No stiff
    > or twisted links. There may be something wrong with the
    > quicklink, it feels a bit too loose sideways, as if it's meant
    > for a wider chain. Now, if only there'd been some sense of
    > rhytm to when the chain skipped I'd been quite pleased with
    > that find... It also appears as although seemingly symmetrical
    > when viewed from the side the sprockets may not be symmetrical
    > when viewed from the rear, the biggest and smallest appear to
    > have a bevel ground into them, determining their direction of
    > rotation. This might well be a contributing factor to the
    > issues I'm having, although IMO this still doesn't fully
    > explain why it runs so smoothly w/o load and so poorly under
    > load. I'd have imagined seeing at least some skipping or
    > hesitation during the bench runs if this was the cause.


    The dynamics of chain skipping on the driven sprocket are such
    that the skipping will occur only under load. Without
    considerable force holding rollers into the slight recesses in
    the tooth profile, there's no obstacle to the chain feeding
    smoothly onto the sprocket in the area where they come together
    into mesh.

    John
     
  19. dabac

    dabac Well-Known Member

    Joined:
    Sep 16, 2003
    Messages:
    2,274
    Likes Received:
    138
    Took the sprockets off yesterday, gave them all another good look, flipped over, laid together and compared tooth flanks back and forth.
    Only visible difference is the (originally) backwards facing corners on the top of teeth on the biggest sprockets, which seems to be chipped.

    Reassembled in the original orientation(the one with the visible surface wear), went for a ride. Smallest procket skips when out of the saddle, but as long as I remain seated it's as smooth as anything. biggest sprocket skipping gone entirely.

    I guess the cynics had it right with: "no good deed goes unpunished".
    I really thought I was doing a sensible thing when I flipped the sprockets over before bringing this hub into service again.
    New rim, new spokes, new chain, new bike, and a new set of tooth flanks to wear on - made sense to me.

    Hopefully the return to the original orientation will keep the bike behaving long enough for me to get the summer bike together. Then I'll have something to ride while I decide how to graft a Shimano body onto this hub and hopefully get it done before winter and the need for studded tires returns.
     
Loading...
Loading...