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Old September 9th 09, 03:03 AM posted to rec.bicycles.tech
Steve Sr.
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Posts: 203
Default Keep Breaking Shifter Cables - Why?

On Mon, 7 Sep 2009 22:40:35 -0700, "Mike Jacoubowsky"
wrote:

"Steve Sr." wrote in message
.. .
Hello,

I have a 10-speed Ultegra equipped road bike in which the rear
deraileur cable keeps breaking strands near the shifter which
necessitates a cable replacement. The broken strands occur about 3/4"
from the barrel. This is currently happening every 3000 miles or so.

Originally I was using Jagwire replacement wires as that seems to be
what most local shops now carry. At the last replacement I decided to
opt for real Shimano inner wires. When removing the old cable I
compared the cable diameter and found that the Jagwire inner wires
were .010-.015" smaller in diameter compared to the new Shimano inner
wire. Also at this time I replaced the plastic ferrules with the
aluminum variety as recommended by the LBS that sold me the cable.

Fast forward about 6 months. This weekend I was cleaning and
inspecting the bike in preparation for the upcoming MS 150 event next
weekend. Much to my surprise I found a broken strand in the new
Shimano cable necessitating yet another cable replacement.

When removing the old cable rather than unwinding the broken strand I
picked up a pair of regular needle nose pliers that happened to have
side cutters built in and to my amazement these cutters went right
through the cable! In the past I can remember these steel cables being
un-cutable by this method. For identification purposes the side of
the cable barrel has an "R" stamped in the side of it.

So is this a characteristic of the newer cables or does Shimano have
several different grades of shifter cables? If so how do I know which
one best and which one I am getting?

Any other things that I should check that might be causing these
premature cable failures?


Thanks,

Steve


One of the variables we've recently found responsible for shortening cable
life is the use of drink mixes in the downtube water bottle, which will
sometimes get on the gear cable and run down to the bottom bracket cable
guide, where it will cause a lot of increased friction in the system.
Another is worn shift cable housing; I'd recommend replacing the housing at
the same time as the cable. And if neither of those are responsible for your
cables breaking, it's possible you have a lever that simply likes to eat
cables. Shimano admits that there are some out there, and they'll replace,
on a case-by-case basis, levers that are no longer functional because a
cable has broken off inside the lever and the head cannot be removed.

--Mike Jacoubowsky
Chain Reaction Bicycles
www.ChainReaction.com
Redwood City & Los Altos, CA USA


Mike,

I know about the sports drink issue and don't believe that this is a
contributing factor in my case.

The lever is probably about 2-3 years old right now so out of warranty
unless it is extended for this issue. So far I have been able to catch
the failures without completely breaking a cable and getting the head
stuck in the shifter. One broken strand is enough to be noticeable. I
cant see how anyone could let it go to complete cable breakage without
noticing shifting issues.

Steve
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