Chain skipping on large chain ring.

The chain is brand new... It is not a used chain... The box it came in
was sealed and it still had that plastic thing at one end to identify
the special link that has to be connected... It still had the factory
grease on it... I installed it myself so I am positive about this...

Worst case scenario, I'll just replace the rings, cassette and chain
all in one go... Although, since it worked so well today, I'll probably
wait until what I have is unusable before I do this...

--
Mike (Xyzzy)

PS - If it would help with the diagnosis, I can easily remove the chain
rings and photograph them on a piece of white paper... Let me know if
this will help and I will do it...

--
Mike (Xyzzy)

Michael Vang writes:

The chain is brand new... It is not a used chain... The box it came
in was sealed and it still had that plastic thing at one end to
identify the special link that has to be connected... It still had
the factory grease on it... I installed it myself so I am positive
about this...

Pictu http://www.teamendorphin.com/jpg/skip.jpg
Pictu http://home.comcast.net/~carlfogel/download/zzz_006.jpg

The chain in the first picture is out of pitch. Someone must have
cleverly traded his used chain for a new one in that box before you
got it. Otherwise how can you explain that the chain is almost a half
pitch ahead of where it ought to be where it exits from the large
chainwheel in your picture. Believe me, that chain is out of pitch.
Please stretch the chain on the floor with a ruler next to it with an
inch mark aligned with the center of a pin, so we can see a photograph
of a 12" section.

I suppose you are aware that the standard ruler is the best chain
gauge you can get. It can't be fooled.

Worst case scenario, I'll just replace the rings, cassette and chain
all in one go... Although, since it worked so well today, I'll
probably wait until what I have is unusable before I do this...

Well if money is no obstacle you might add new derailleurs and shift
levers to that gratuitous purchase. Don't do it, and watch out for
those "twisty little passages all alike!" not to be confused with
"twisty little passages all different!" That's amazing.

Jobst Brandt

Just to clarify, the chain rides up only when I pedal backwards very
slowly... I assume this is more the rear derailleur spring tension
being overcome than the pitch of the chain being off... IOW, if this
was a single speed bike with no slack in the chain this would not
happen at all, right? If the pitch was off wouldn't the chain fit
poorly all the way around? And if the pitch was off, wouldn't I have
poblems with the cassette and small ring? Finally, wouldn't a worn
chain be longer? The new chain is shorter than the old chain, and the
old (longer/worn) chain never rode up like this...

--
Mike (Xyzzy)

Michael Vang writes:

Just to clarify, the chain rides up only when I pedal backwards very
slowly... I assume this is more the rear derailleur spring tension
being overcome than the pitch of the chain being off... IOW, if
this was a single speed bike with no slack in the chain this would
not happen at all, right? If the pitch was off wouldn't the chain
fit poorly all the way around? And if the pitch was off, wouldn't I
have problems with the cassette and small ring? Finally, wouldn't a
worn chain be longer? The new chain is shorter than the old chain,
and the old (longer/worn) chain never rode up like this...

The chain in your picture got where it is from forward pedaling and
the incoming chain lands in the root of the first tooth. Thereafter,
because it is tensioned by the rear derailleur and it has a longer
pitch than 1/2 inch that the chainwheel has, it climbs out of
engagement and rides over the teeth of the sprocket.

As you can see from the chainwheel picture I offered, worn teeth are
obvious and as I mentioned, will work with a new chain that is
in-pitch (1/2 inch). If you have the time to do so, pleas post a
picture of the chain lying stretched adjacent to a yardstick or other
inch rule.

The chins shown in you picture also has exaggerated wear marks on the
side plates as though it had been ridding in horrible chain alignment
as would occur with riding small sprocket to small chainwheel or the
opposite. I have never seen a chain with such worn side plates.

Jobst Brandt

I don't have a metal rule, but here are some pictures with a wooden
rule... I have no idea what effect humidity and stuff has had on the
ruler but it matches up exactly with my metal tape measure... I would
have used the metal tape measure for this but I don't have enough hands
to hold the ruler taut and flat, the camera and the chain...

http://www.teamendorphin.com/jpg/oldchain1.jpg
http://www.teamendorphin.com/jpg/oldchain12.jpg
http://www.teamendorphin.com/jpg/newchain1.jpg
http://www.teamendorphin.com/jpg/newchain12.jpg

I was not able to remove the new chain because it is joined with a
one-time link pin... I hope this is okay...

I'm not the kind of guy who buys stuff for no reason... In fact, I am
pretty frugal... I'd only buy a new complete drivetrain if the existing
one was ruined... I definitely wouldn't play around with replacing
individual parts and then ruining those parts when they mesh with the
old parts... I'd rather just start fresh with a clean slate and do it
right, if that is what is needed to be done...

My overwhelming priority is to make this bike servicable and safe... It
is far from being a hangar queen...

BTW, I am aware that a ruler is the best way to measure a chain, but
the CC-2 is so convenient... If I find the CC-2 has been wrong all
along I will be pretty bummed out...

http://www.parktool.com/tools/CC_2.shtml

--
Mike (Xyzzy)

wrote:

The chain in the first picture is out of pitch.

Could the new chain be out of tolerance, and slightly too short?
Surely, this would be most inclined to show up as skipping on
the largest chainring.

John

The chins shown in you picture also has exaggerated wear marks on the
side plates as though it had been ridding in horrible chain alignment
as would occur with riding small sprocket to small chainwheel or the
opposite. I have never seen a chain with such worn side plates.

Which picture? This one?

http://www.teamendorphin.com/jpg/skip.jpg

That is the new chain! How can the side plates be worn? When I opened
the box, it had the official Campy seal on it, the plastic thingy on
the end to mark the special link hole, the factory grease and it was
like 114 links long... How could this be a used chain?

I'm lost here!



--
Mike (Xyzzy)

Michael Vang writes:

I don't have a metal rule, but here are some pictures with a wooden
rule... I have no idea what effect humidity and stuff has had on the
ruler but it matches up exactly with my metal tape measure... I
would have used the metal tape measure for this but I don't have
enough hands to hold the ruler taut and flat, the camera and the
chain...

http://www.teamendorphin.com/jpg/oldchain1.jpg
http://www.teamendorphin.com/jpg/oldchain12.jpg
http://www.teamendorphin.com/jpg/newchain1.jpg
http://www.teamendorphin.com/jpg/newchain12.jpg

I was not able to remove the new chain because it is joined with a
one-time link pin... I hope this is okay...

This is not OK. I understand now that the measurement method is not
adequately defined. Lay the chain out flat on a wooden floor with a
ruler, yard stick or other inch graduated rule having its markings
touching the side of the chain:

O==O==O==O==O==O==O==O==O==O==O==O==O==O==O==O==O= =O==O==O==O==O==O==O - chain
| | | | | | | | | | | | | | | | | | | | | | | | - ruler
1 2 3 4 5 6 7 8 9 10 11 12
STANLEY (INCH RULE)
__________________________________________________ ____________________

Take a picture of this arrangement from at least four feet distance
with the lens zoomed in to show at least 10 inches of chain. A new
chain should appear like the diagram above with a pin/roller at every
1/2 inch mark. That is what needs to be observed 10 inches from the
initial alignment point.

BTW, I am aware that a ruler is the best way to measure a chain, but
the CC-2 is so convenient... If I find the CC-2 has been wrong all
along I will be pretty bummed out...

From you pictures I take it you don't use the ruler method because
the pictures do not show the measurement of interest.

http://www.parktool.com/tools/CC_2.shtml

It measures too short a distance to give a good sample of chain and it
must be engaged in the correct roller pair.


Jobst Brandt

John Henderson writes:

The chain in the first picture is out of pitch.

Could the new chain be out of tolerance, and slightly too short?
Surely, this would be most inclined to show up as skipping on the
largest chainring.

No. It is not possible to make a chain that is out of pitch with the
machines that make chains. There may be a botched link in there that
would come around in what seems to be a random manner, the chain
length not being any multiple of the crank rotation.

Jobst Brandt