CHAIN JUMPS PAST REAR GEARS
July 30, 2007
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I have followed the recommended
way to adjust the rear dérailleur and it shifts okayexcept
in the center of the cogset the chain jumps past a cog as
I shift to a lower gear. Starting from the smallest and
counting toward the largest it happens about cog 5 or 6
and jumps to 7 or 8. It's a Campy Centaur 10-speed. Any
help would be appreciated. Thanks.
As I've said before, walking someone
thru diagnosis of an unobvious problem via the written word
has problems of its own. But I've geared up for this one.
I suspect one of three things: (1)
a bad derailleur cable and/or housing; (2) excessively worn
teeth on one or more cogs; or (3) a bad angle or tension
of the rear derailleur.
Number (1) you can address most
easily. Try replacing the cable and its housing. If the
problem persists, lay the bike on its side (gears facing
up) under really good light and inspect the teeth on the
middle cogs. Each tooth should have sharp corners, not rounded.
Rounded teeth means you should replace the entire cassette
(or freewheel); when you do, you must also replace the chain.
If the teeth pass your check-up,
you might check the angle of the derailleur relative to
the cogs. I could try to explain that, but, as we often
find, the folks at Park
Tool have it covered pretty well.
Failing all that, the derailleur
might have a more subtle problem, like a bad spring, misaligned
jockey wheel, or a loose bolt. (Some might even blame the
shifter.) For these sorts of things I'd seek professional
(I mean, well-paid) help.