Chain skipping under load(for no obvious reason)

[dabac]

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

[Jay Beattie]

On Mar 31, 3:04*am, dabac <dabac.374...@no-
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.

[andresmuro@aol.com]

On Mar 31, 4:04 am, dabac <dabac.374...@no-
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

[John Henderson]

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

[DanKMTB@gmail.com]

On Mar 31, 2:26*pm, Jay Beattie <jbeat...@lindsayhart.com> wrote:
> On Mar 31, 3:04*am, dabac <dabac.374...@no-
>
>
>
>
>
> 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.

[dabac]

Jay Beattie Wrote:
> ..make sure your cable guide under the BB is well
> greased. Easy enough, will do.

Jay Beattie Wrote:
> ..Sometimes cable sticking can give you a problem that seems like a bad
> cog/chain combo. But wouldn't that simply cause the RD to hesitate a little when
downshifting?
Jay Beattie Wrote:
> .. Other problems may be: (1) bent
> derailleur hanger, (2) bad derailleur (unlikely), (3) unseen stiff
> link, (4) unseen wear on cogs,

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.

Jay Beattie Wrote:
> ... Make sure you did
> not sin in a past life.

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.


--
dabac

[Leo Lichtman]

"John Henderson" wrote: (clip) make sure your
> chain doesn't have a twist in it. (clip)
^^^^^^^^^^^^^^^^^
Moebius chain will do it every time.

[dabac]

John Henderson Wrote:
> Jay Beattie wrote:
> [color=blue]
>
> 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

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.


--
dabac

[dabac]

DanKMTB@gmail.com Wrote:
>
> I had this problem last season for a couple rides of troubleshooting.
> Like Jay says, it was the cable.

Thanks for the tips guys, This afternoon I have another 16-mile chance
to figure it out...


--
dabac

[dabac]

andresmuro@aol.com Wrote:
> Used sprockets don't work with new chains.
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.

andresmuro@aol.com Wrote:
> ... toss the cassette and get a new one.
> 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.

andresmuro@aol.com Wrote:
> Your chains and cassette will work together for several thousand miles.

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


--
dabac

[John Henderson]

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

[jobst.brandt@stanfordalumni.org]

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

[John Henderson]

jobst.brandt@stanfordalumni.org 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

[Lou Holtman]

John Henderson wrote:
> jobst.brandt@stanfordalumni.org 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

[Jay Beattie]

On Apr 2, 2:19*pm, Lou Holtman <lholremovet...@planet.nl> wrote:
> John Henderson wrote:
> > jobst.bra...@stanfordalumni.org 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.

[jobst.brandt@stanfordalumni.org]

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

[dabac]

jobst.brandt@stanfordalumni.org Wrote:
> ..Inspecting sprocket that has
> been run with a badly worn chain will reveal the backs of teeth as
> shiny and worn.

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.


--
dabac

[John Henderson]

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

[dabac]

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.


--
dabac