Steve Sr. wrote:
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?

Both Shimano and Jaguar make various grades of gear wire.
Do you replace the casing with a new wire?

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971