I have a new 10 speed shimano 12-27 cassette and KMC chain on a brand new
Specialized Roubaix Expert Double (stands for double chain ring). I would
think about taking the bike back to the LBS where I bought this bike, but I
am worrried that the techs there won't really know what to do, or tell me
that my problem is the limitation of the 10 spd cassette system, because
they won't know how to solve the problem, so before I go back to them, I
would like to either try to fix the problems myself or at least know what to
say that they might consider to solve the problem.
I have two problems:
1) When the KMC chain connector just begins to engage the smallest cog
(12t) on the cassette, it gets temporarily hung up by slightly rubbing on
the side of a second cog tooth. The snap-link pin seems slightly too wide
to smoothly fit between the first and second cog, and it is thus prevented
from falling onto the arrriving tooth of the cassette. The snap-link pin
seems slightly longer than the fixed pins on the remainder of the chain
because the only place that the chain holds up is at the snap-link. As the
cassette further turns and the pressure on the chain to descend over the
tooth on the first cog gets greater, the chain finally clunks down over the
tooth and continues around the cassette, disengaging without any visible
problems. This results in a repetitive clunking at high speeds that sounds
terrible and is annoying. I have tried to slightly sand down the sharp edge
of the pin top on the link so that it might slide more easily onto the tooth
but it still holds up. Reversing the links does not change the problem. (I
was hoping one of the two links might have been slightly out of spec.)
Also, when backpedaling, the same problem occurs when the chain engages the
tooth at the top of the cassette as it moves counterclockwise. I could try
filing the top of the pin down but that looks risky as it seems it will
weaken the connection.
Is this a problem with a (?mismanufacturered) KMC link, or other some
other problem?
2) On the the biggest cog (27t) the derailleur pulley rings are too
close to the teeth of the cog causing a rumbling as the pulley rings and the
cassette rings slightly exert pressure on each other through the chain as it
runs between the two. I examined removing one chain link to "pull-down" the
pulley wheel away from the cassette but that would result in the derailleur
spring being stretched beyond its furthest extension.
Any ideas on this one other than getting a 12-25 cassette or 11-23?