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Old May 4th 05, 04:56 PM
Mike Jacoubowsky
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I'm having problems (again) shifting from my middle to granny under load.
I just replaced my moderately worn 40t middle with a new 38t, and the
problem crept up again. I have already taken the measures of filing away
the portion of the derailer that conatcts the frame, filing a small groove
in the seat tube itself, and even moving my chainline outward about a mm
via a BB spacer, and still no success. It shifts fine when not under
load, but once you start up an incline, forget it, it won't go. Its an
Ultegra der. and TA Alize rings.


The greater the gap between the largest two chainrings, the more difficulty
there will be shifting from the middle to the smallest. That's an absolute
fact of life, regardless of what you may read elsewhere. That doesn't mean
you can't make it work better than it presently does (by using a derailleur
designed for a smaller middle chainring, such as Peter/Qui si parla
Campagnolo suggested). Or it might work better if you bring down the size of
the largest chainring, although at some point you have the curve of the
derailleur not matching up to the radius of the outer chainring, which will
also cause shifting issues.

With the DuraAce 9-speed triple (with 52/39/30), Shimano tried to get around
this by cutting down the profile of the teeth on the middle chainring.
Unfortunately, it was/is legendary for dumping the chain off the middle
chainring as you're "just riding along." The shifting was terrible compared
to the Ultegra 52/42/30. However, for the new Ultegra 10, they seem to have
gotten their act together and the 52/39/30 shifts quite nicely. Dramatic
improvement. But it also has a highly-convoluted middle chainring that would
be difficult to duplicate with your dremel tool, *and* will probably wear
out more quickly too.

Please note these problems are exacerbated by STI shifting, which doesn't
allow you to control the shifting process as much as Ergo or friction.
They're also far pickier about chain choice and, I daresay, if you're using
an SRAM chain, you may have better results with a Shimano.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com


"Kyle.B.H." wrote in message
...
I'm having problems (again) shifting from my middle to granny under load.
I just replaced my moderately worn 40t middle with a new 38t, and the
problem crept up again. I have already taken the measures of filing away
the portion of the derailer that conatcts the frame, filing a small groove
in the seat tube itself, and even moving my chainline outward about a mm
via a BB spacer, and still no success. It shifts fine when not under
load, but once you start up an incline, forget it, it won't go. Its an
Ultegra der. and TA Alize rings.

So now I'm thinking I'll file the tops off of two consectutive teeth in
the middle ring to aid the shift. Don't some chainrings include this as a
feature?

A) Think this will help?

B) If I do this, where on the ring (relative to the right crankarm) would
I file the teeth?

C) Any other suggestions?

Thanks,

Kyle



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