Sudden chain skip

Ron Hardin said:

After rusting in a day after a rain/salt water/snow commute, and
getting re-WD40'd, the chain skips on all rear cogs, but least
on the largest ones; and on all front sprockets. The skipping though
is in the rear in all cases.

A very stretched chain, which ought to mean that it won't skip except
for popping off the sprockets on the front eventually, if anything.

I'm trying to guess the cause. A reduced derailleur springiness was
my best guess, but it seems to be okay.

The fix of course is replace the chain and freewheel, but I was going
to wait until the road salt season was over.

PS there don't seem to be any stiff links.

--
Ron Hardin
[email hidden]

On the internet, nobody knows you're a jerk.

Ron Hardin said:

After rusting in a day after a rain/salt water/snow commute, and
getting re-WD40'd, the chain skips on all rear cogs, but least
on the largest ones; and on all front sprockets. The skipping though
is in the rear in all cases.

I'm trying to guess the cause. A reduced derailleur springiness was
my best guess, but it seems to be okay.

Check the jockey wheels as well. Mine got gummed up after being ridden
through more snow than they cared for, and the chain would seem to
skip; it was really the tension in the chain pulling on the derailleur,
which would eventually snap back into position, as if it were shifting.
I could see it rather evidently when back-pedalling as well; the wheels
spun so slowly that the chain would droop onto the chainstays.

A shot of WD-40, a touch of oil, and a night in a warm, dry basement
should do the trick.

--

__o Kristian Zoerhoff
_'\(,_ [email hidden]
(_)/ (_)

Ron Hardin said:

After rusting in a day after a rain/salt water/snow commute, and
getting re-WD40'd, the chain skips on all rear cogs, but least
on the largest ones; and on all front sprockets. The skipping though
is in the rear in all cases.

Quoted message said:

A very stretched chain, which ought to mean that it won't skip except
for popping off the sprockets on the front eventually, if anything.

Quoted message said:

I'm trying to guess the cause. A reduced derailleur springiness was
my best guess, but it seems to be okay.

Quoted message said:

The fix of course is replace the chain and freewheel, but I was going
to wait until the road salt season was over.

I think there is no oil in your chain, considering that it worked OK
in the wet and before. There may be no tight links in the chain but
that won't prevent it from galling and not articulating when coming
off the zig-zag course it threads through the derailleur. Before you
throw out the chain, lubricate it by manually pedaling it backward
while dribbling (30W) oil on it as it goes by.

After that, get a new chain and as many sprockets as are necessary.
It's almost spring time and more miles.

Jobst Brandt

Y'know, today I got to ride it in the sunlight (so there is a shadow
of the chainring to see what's going on), and while I can't see it
jump either in front or back, I'm beginning to suspect the front.

There's a couple things in its favor, and a couple things against it.

In favor of the front, there's clear daylight between chain and
chainwheel, and under load the daylight on the bottom of the
chainwheel gets smaller. This means that the chain is slipping
on the chainwheel, maybe enough (?) to make it clear an oncoming
tooth on top. The theory then is that the general gunk and crud
kept the chain from slipping on its respective teeth and so prevented
the extra slack from appearing at the top of the chainwheel, and oiling
the thing (to get rid of visible sudden rust) broke that spell. A
dry chain is a happy chain.

Against the front, (1) the chain stays on the chainwheel it's on
rather than popping off, and (2) it skips on the smaller chainwheels
which have no wear on them at all more easily than on the large
chainwheel which is visibly worn.

It skips on the smaller rear cogs much more than the large ones,
so apparently at least the derailleur tension seems to keep it happy,
and that tension ought to make the chainwheel slippage worse rather
than better.

So I don't have a good theory.

What I'll try, for the fun of it, is weaving some string back and forth
across the chainwheel tooth gaps, so as to encourage the former daylight
to stay evenly distributed, and see if that reduces the skipping.

It only skips under load, so you can't watch it very carefully.
--
Ron Hardin
[email hidden]

On the internet, nobody knows you're a jerk.

Quoted message said:

What I'll try, for the fun of it, is weaving some string back and forth
across the chainwheel tooth gaps, so as to encourage the former daylight
to stay evenly distributed, and see if that reduces the skipping.

Why not just try Jobst's idea of lubricating the chain? Seems a lot simpler.

--Mike Jacoubowsky
Chain Reaction Bicycles
www.ChainReaction.com
Redwood City & Los Altos, CA USA

jobst.brandt said:

Ron Hardin said:

After rusting in a day after a rain/salt water/snow commute, and
getting re-WD40'd, the chain skips on all rear cogs, but least
on the largest ones; and on all front sprockets. The skipping though
is in the rear in all cases.

Quoted message said:

A very stretched chain, which ought to mean that it won't skip except
for popping off the sprockets on the front eventually, if anything.

Quoted message said:

I'm trying to guess the cause. A reduced derailleur springiness was
my best guess, but it seems to be okay.

Quoted message said:

The fix of course is replace the chain and freewheel, but I was going
to wait until the road salt season was over.

I think there is no oil in your chain, considering that it worked OK
in the wet and before. There may be no tight links in the chain but
that won't prevent it from galling and not articulating when coming
off the zig-zag course it threads through the derailleur. Before you
throw out the chain, lubricate it by manually pedaling it backward
while dribbling (30W) oil on it as it goes by.

After that, get a new chain and as many sprockets as are necessary.
It's almost spring time and more miles.

I'm with Jobst on this.

Also check (and lubricate) your cables. Sticky cables can stall upshifts
that eventually happen later, and feel like the chain is skipping.

Matt O.

I'll try oil if the string thing doesn't work. The chain seems
to run pretty smoothly to me, through the derailleur ; also the
WD-40 lubes it. If anything, I want less lube, on my current theory.
--
Ron Hardin
[email hidden]

On the internet, nobody knows you're a jerk.

Ron Hardin said:

I'll try oil if the string thing doesn't work. The chain seems to
run pretty smoothly to me, through the derailleur ; also the WD-40
lubes it. If anything, I want less lube, on my current theory.

I don't understand what your string is supposed to do nor why you
don't want to put some oil on the chain. Consider that it ran fine
when wet with water and then after standing around began to skip. The
only thing that changed is that the lubricant (water) dried off. As I
have often mentioned, water is a good lubricant, but you can't keep it
in place once the rain stops, so we use low volatility viscous oil so
it won't evaporate and will cling to the capillary gaps in the chain.

You know the old promo "tenacious" oil. Aren't they all?

Jobst Brandt

Ron Hardin said:

I'll try oil if the string thing doesn't work. The chain seems
to run pretty smoothly to me, through the derailleur ; also the
WD-40 lubes it. If anything, I want less lube, on my current theory.

In our experience, that group of aerosol products will quickly, easily
and effectively rinse out the oil from under the rollers - which is
where you want lube. The result is a chain much more subject to water
and salt water penetration and hence faster wear.

We use oil instead. Wet the chain, then wipe off any oil on the
outside- which is doing nothing but attracting dirt anyway.

p.s. string is pointless and silly.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Andrew Muzi said:

Quoted message said:

I'll try oil if the string thing doesn't work. The chain seems to
run pretty smoothly to me, through the derailleur; also the WD-40
lubes it. If anything, I want less lube, on my current theory.

Quoted message said:

In our experience, that group of aerosol products will quickly,
easily and effectively rinse out the oil from under the rollers -
which is where you want lube. The result is a chain much more
subject to water and salt water penetration and hence faster wear.

Quoted message said:

We use oil instead. Wet the chain, then wipe off any oil on the
outside- which is doing nothing but attracting dirt anyway.

Quoted message said:

p.s. string is pointless and silly.

Hey! I can't get away with saying that (and don't), how do you do
that? Where's Carl when we need him? Oh, he's out of uniform at the
moment and can't attend to this.

Jobst Brandt

Quoted message said:

Andrew Muzi said:

Quoted message said:

I'll try oil if the string thing doesn't work. The chain seems to
run pretty smoothly to me, through the derailleur; also the WD-40
lubes it. If anything, I want less lube, on my current theory.

Quoted message said:

In our experience, that group of aerosol products will quickly,
easily and effectively rinse out the oil from under the rollers -
which is where you want lube. The result is a chain much more
subject to water and salt water penetration and hence faster wear.

Quoted message said:

We use oil instead. Wet the chain, then wipe off any oil on the
outside- which is doing nothing but attracting dirt anyway.

Quoted message said:

p.s. string is pointless and silly.

Hey! I can't get away with saying that (and don't), how do you do
that? Where's Carl when we need him? Oh, he's out of uniform at the
moment and can't attend to this.

Jobst Brandt

Dear Jobst,

Actually, I looked at the thread when it started, but decided that he
didn't follow which gears were skipping when, and deleted the thread.

Then I saw the comment about the string and wondered what on earth
people were talking about.

Now I'm going to turn the tables on everyone and ask them to provide a
link to whatever the hell the silly, pointless string is supposed to
do to a skipping chain.

After all, I've provided links to plenty of equally weird things, so
it's only fair that someone else call up Google Groups, find the
individual post (not just the thread, please), and point me down the
path to true understanding.

I could have done it myself more quickly, but scribbling this s more
fun, and it will be interesting to see if anyone provides a direct
link.

I'm sinfully proud of not making any puns about threads and strings,
but I'm utterly baffled as to what a string can do to a skipping chain
and sprockets.

Cheers,

Carl Fogel

For Carl Fogel....

Ron Hardin said:

Y'know, today I got to ride it in the sunlight (so there is a shadow
of the chainring to see what's going on), and while I can't see it
jump either in front or back, I'm beginning to suspect the front.

Quoted message said:

There's a couple things in its favor, and a couple things against
it.

Quoted message said:

In favor of the front, there's clear daylight between chain and
chainwheel, and under load the daylight on the bottom of the
chainwheel gets smaller. This means that the chain is slipping on
the chainwheel, maybe enough (?) to make it clear an oncoming tooth
on top. The theory then is that the general gunk and crud kept the
chain from slipping on its respective teeth and so prevented the
extra slack from appearing at the top of the chainwheel, and oiling
the thing (to get rid of visible sudden rust) broke that spell. A
dry chain is a happy chain.

Quoted message said:

Against the front, (1) the chain stays on the chainwheel it's on
rather than popping off, and (2) it skips on the smaller chainwheels
which have no wear on them at all more easily than on the large
chainwheel which is visibly worn.

Quoted message said:

It skips on the smaller rear cogs much more than the large ones, so
apparently at least the derailleur tension seems to keep it happy,
and that tension ought to make the chainwheel slippage worse rather
than better.

Quoted message said:

So I don't have a good theory.

Quoted message said:

What I'll try, for the fun of it, is weaving some string back and
forth across the chainwheel tooth gaps, so as to encourage the
former daylight to stay evenly distributed, and see if that reduces
the skipping.

Quoted message said:

It only skips under load, so you can't watch it very carefully. --
Ron Hardin [email hidden]

Quoted message said:

On the internet, nobody knows you're a jerk.

Jobst Brandt

Quoted message said:

For Carl Fogel....

Ron Hardin writes:

[snip]

Quoted message said:

Quoted message said:

What I'll try, for the fun of it, is weaving some string back and
forth across the chainwheel tooth gaps, so as to encourage the
former daylight to stay evenly distributed, and see if that reduces
the skipping.

[snip]

Quoted message said:

Jobst Brandt

Dear Jobst,

Thanks!

Is this string-in-the-front-sprockets a well-known practice that you
and Ron and Andrew are all familiar with, like tying and soldering,
but which I've never heard of?

Or just a truly inspired original idea from Ron?

My naive reaction is to say sorry, Orville, that won't fly.

But I admit that I've never wrapped string around my front sprockets,
so Ron may astonish us all.

Cheers,

Carl Fogel

Quoted message said:

Ron Hardin said:

I'll try oil if the string thing doesn't work. The chain seems to
run pretty smoothly to me, through the derailleur ; also the WD-40
lubes it. If anything, I want less lube, on my current theory.

I don't understand what your string is supposed to do nor why you
don't want to put some oil on the chain. Consider that it ran fine
when wet with water and then after standing around began to skip. The
only thing that changed is that the lubricant (water) dried off. As I
have often mentioned, water is a good lubricant, but you can't keep it
in place once the rain stops, so we use low volatility viscous oil so
it won't evaporate and will cling to the capillary gaps in the chain.

You know the old promo "tenacious" oil. Aren't they all?

Jobst Brandt

I want to try my theory first because it depends on restoring _increased_
friction that likely existed between chain and chainwheel before I WD-40'd
it. That is, the other thing that changed suddenly is that the chain is
suddenly lubed up. (Also the chain seems to run smoothly on the derailleur,
so it's doubtful, albeit not impossible, that it's seizing up somehow there.)

My theory is that the daylight between chain and chainwheel (owing to the
stretched chain) is no longer stable because the chain is more likely to
slip on the chainwheel teeth at the bottom, resulting in too much slack
at the top, under load, for the oncoming tooth.

The woven string is meant to fill in the daylight gaps and so prevent the chain
from slipping into them, and so producing slack at the oncoming tooth at
the top. It either works or it doesn't. I'll try it when it warms up today.
--
Ron Hardin
[email hidden]

On the internet, nobody knows you're a jerk.

Well, I fixed it. This involved though replacing chain, freewheel and
derailleur.

The string didn't help, though it made the thing slightly smoother.

It turns out the trouble was a frozen lower joint on the derailleur, so
frozen solid in fact that I couldn't determine that it was intended
to pivot at all (forcing it didn't produce any motion).

The upper pivot worked fine, and things seemed normal. But the effect
was that the chain travel length over the rear cogs was reduced, and
this produced the skip. Apparently the rain did in the last bit
of necessary play in that joint, and froze it really really solid.

Later with vise and 12" wrench I managed to free the frozen joint,
to verify that it was in fact intended to pivot.

I found a spare freewheel, and put it in, with 8sp chain from another
junkbox. Surprise, it was a 6sp freewheel (who counts?), which was
okay except it screwed itself into the spoke guard and left me with
no freewheeling. Okay, search junkbox more, find 7sp freewheel (I
tend to buy extras when I buy one, so there always unknown unused
bike parts somewhere if you look long enough). That worked okay,
if a washer was added between freewheel and rear dropout.

Note to self : buy a collection of assorted bike axle washers.

Executive summary : derailleur froze up.
--
Ron Hardin
[email hidden]

On the internet, nobody knows you're a jerk.