Perplexing Chainline Problem. (long)

http://www.sheldonbrown.com/speeds.html

Brian Phillips said:

I recently upgraded from Ultegra 9 speed to 10 speed by replacing the
shifters, chain and rear derailleur.

The old rear der would have done the job just fine.

Quoted message said:

The bike is shifting great (Shimano
chain & cassette), but I'm having a problem with the chain staying in the
big ring whenever I'm in any of the 3 largest cassette cogs (the 23-21-19).

Not to put too fine a point on this barbed comment....don't do that!
Running the chain across the big/big and small/small combinations just
wears it out faster; there are other gear pairs that will do the job
with a straighter chainline.

Quoted message said:

The chainline looks pretty radical when it's in any of those gears,

Yup. This is a Clue.

Quoted message said:

and as
the cranks are turned, the chain has a tendency to want to jump down into
the small ring (and it will if I keep turning it over long enough) even
though the front derailleur isn't coming into contact with the chain in any
way. It seems that the chain is being forced onto the small ring due to the
sharp chainline.

Indeed. It also means that you probably need to readjust the front
der a bit.

Quoted message said:

I don't recall what the chainline looked like in those gears before with the
9 speed setup, but I could ride in the 53x21 without any problems other than
a little noise I flexed the frame too much.

The "little noise" should have been the chain rubbing on the front
der.

Quoted message said:

Theory #1:
Now, I still have the old Ultegra cranks and chainrings on the bike. While I
was installing the 10 speed stuff I did take off the cranks to clean them,
then put them back on. Is it possible that, even though I've cranked down on
the bolt as hard as I could, that the crank somehow isn't as far in to the
bottom bracket as it was before I removed it?

Possibly. Is this an Octalink or a square taper BB? With a square
taper, as you ride, the tendency (if the bolt remains tight) is for
the crank to work farther onto the BB shaft. With Octalink, it should
go to the same spot every time. I don't recall if Ultegra groups
still had square tapers when the 9sp version came out.

Quoted message said:

I pulled it off again and
re-installed it, re-torqued the allen bolt, but can't get it to move any
further in, and it is on properly. On my first ride, the chain did come off
the small ring once and fell off around the bottom bracket shell, suggesting
this theory might be possible.

What it most strongly suggests is that you need to readjust the front
der, both the stop settings and the cable.

Quoted message said:

However, it doesn't seem like there would be
any reason for the crank to be so much further out that it would cause this
problem.

Theory #2:
My big ring, which has about 10,000 miles on it, is worn to the point where,
with the new narrower chain, I'm experiencing a problem that wouldn't happen
with a slightly worn 9 speed chain. I've never had a problem wearing out a
big ring before, but I guess that's possible...

A front sprocket worn enough to cause a problem will usually skip or
go into chainsuck mode in my experience, not derail inwards. However,
given the mileage, check it for wear anyway.

Quoted message said:

Theory #3:
Some other compatibility problem with using the chainrings from the old 9 sp
eed stuff with the 10 speed chain?

This is a non-issue.

Readjust the front der. And don'r ride in the big/big and small/small
pairs.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Brian Phillips said:

I recently upgraded from Ultegra 9 speed to 10 speed by replacing the
shifters, chain and rear derailleur. The bike is shifting great (Shimano
chain & cassette), but I'm having a problem with the chain staying in the
big ring whenever I'm in any of the 3 largest cassette cogs (the 23-21-19).
The chainline looks pretty radical when it's in any of those gears, and as
the cranks are turned, the chain has a tendency to want to jump down into
the small ring (and it will if I keep turning it over long enough) even
though the front derailleur isn't coming into contact with the chain in any
way. It seems that the chain is being forced onto the small ring due to the
sharp chainline.

I don't recall what the chainline looked like in those gears before with the
9 speed setup, but I could ride in the 53x21 without any problems other than
a little noise I flexed the frame too much.

Theory #1:
Now, I still have the old Ultegra cranks and chainrings on the bike. While I
was installing the 10 speed stuff I did take off the cranks to clean them,
then put them back on. Is it possible that, even though I've cranked down on
the bolt as hard as I could, that the crank somehow isn't as far in to the
bottom bracket as it was before I removed it? I pulled it off again and
re-installed it, re-torqued the allen bolt, but can't get it to move any
further in, and it is on properly. On my first ride, the chain did come off
the small ring once and fell off around the bottom bracket shell, suggesting
this theory might be possible. However, it doesn't seem like there would be
any reason for the crank to be so much further out that it would cause this
problem.

109.5mm BB spindle? If Octalink, not a 118MM?

Quoted message said:

Theory #2:
My big ring, which has about 10,000 miles on it, is worn to the point where,
with the new narrower chain, I'm experiencing a problem that wouldn't happen
with a slightly worn 9 speed chain. I've never had a problem wearing out a
big ring before, but I guess that's possible...

Theory #3:
Some other compatibility problem with using the chainrings from the old 9 sp
eed stuff with the 10 speed chain?

Any ideas? The chain length is correct.

I would say a BB spindle problem(is the small ring a long way from the
chainstay?) or perhaps a new chain and a worn out big ring...

Andrew F Martin said:

http://www.sheldonbrown.com/speeds.html

Nice article...now how about answering the gent's question?

Brian Phillips said:

I recently upgraded from Ultegra 9 speed to 10 speed by replacing the
shifters, chain and rear derailleur. The bike is shifting great (Shimano
chain & cassette), but I'm having a problem with the chain staying in the
big ring whenever I'm in any of the 3 largest cassette cogs (the 23-21-19).
The chainline looks pretty radical when it's in any of those gears, and as
the cranks are turned, the chain has a tendency to want to jump down into
the small ring (and it will if I keep turning it over long enough) even
though the front derailleur isn't coming into contact with the chain in any
way. It seems that the chain is being forced onto the small ring due to the
sharp chainline.

I don't recall what the chainline looked like in those gears before with the
9 speed setup, but I could ride in the 53x21 without any problems other than
a little noise I flexed the frame too much.

Don't just look, _measure_ the chainline. All you need is an ordinary
ruler. Standard for "road" triples is 45 mm. For doubles, 43.5 mm.

See: http://sheldonbrown.com/chainline

Quoted message said:

Theory #1:
Now, I still have the old Ultegra cranks and chainrings on the bike. While I
was installing the 10 speed stuff I did take off the cranks to clean them,
then put them back on. Is it possible that, even though I've cranked down on
the bolt as hard as I could, that the crank somehow isn't as far in to the
bottom bracket as it was before I removed it?

Naw.

Quoted message said:

Theory #2:
My big ring, which has about 10,000 miles on it, is worn to the point where,
with the new narrower chain, I'm experiencing a problem that wouldn't happen
with a slightly worn 9 speed chain. I've never had a problem wearing out a
big ring before, but I guess that's possible...

Yes it is. Even likely.

Quoted message said:

Theory #3:
Some other compatibility problem with using the chainrings from the old 9 sp
eed stuff with the 10 speed chain?

Nope.

Many newer sporty bikes have ridiculously short chainstays, prompted by
a superstition that believes this somehow makes the bike faster. Such
bikes are less tolerant of cross-chaining than bikes with more
reasonable chainstay length.

Sheldon "Chainline" Brown
+-----------------------------------+
| Habit is the nursery of errors. |
| --Victor Hugo |
+-----------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Qui si parla Campagnolo said:

Andrew F Martin said:

http://www.sheldonbrown.com/speeds.html

Nice article...now how about answering the gent's question?

Hah - I thought I cancelled that post. I was going to say that 9 and
10sp rings were different from what I'd heard from my shop friends
(being that the 10sp chain is thinner), but I think Sheldon's page
refutes that. Whoops.

Brian,

Did you install the spacer that comes with the 10 speed cassette?
It goes on the free hub before you slide on cassette.
If it is not installed you could have the problem you are describing.

Joel

Thanks to all who replied. I should have made it clear that I don't go
riding around in the 53x23, but I do need to use the 53x21 occasionally to
keep from having to go to the small ring... and a 53x19 is the best gear
there is for motoring along, so I've gotta have that. The bike is a 1999
oversize aluminum LeMond Chambery, BTW.

Yes, I did install the spacer for the casette. I ruled out a front
derailleur adjustment issue because it wasn't the front derailleur that was
forcing the chain to leave the big ring; it was doing that with no
assistance whatsoever.
BB spindle width is 109.5.

Sheldon: Checking the chainline according to your measurement (43.5 for a
double) indicates the distance of the rings to the center of the seat tube
is about right, so that was useful information along with everything else on
your site.

The small ring isn't that far away from the chainstay at the closest point.
Maybe 5mm. So, a problem with the crank being too far out from the bb seems
to be ruled out...

I bought a new 53t ring and put it on tonight and tried it on the trainer...
it maybe works a little bit better... turning the cranks over by hand (with
resistance applied to the back wheel) doesn't cause it to jump from the 21
or 19, but if I sit on the bike and stomp on it, the frame flexes enough to
cause the problem of the chain wanting to jump to the small ring. I'll have
to take it for a road ride on the weekend to see.

Could it be that my 6 year old frame has gotten weaker with age, causing
excessive flex? I was under the impression that oversize aluminum frames
stay stiff forever. No Viagra jokes, please.