The nipple of the inner wire is held in a
lever, or shifter, that the rider uses to pull the cable. The other end is clamped in
place on the gear or brake mechanism. Brake cables are slightly fatter than gear cables. Different hand controls use bike cables with
differently shaped nipples. The outer-cable for brakes – sometimes called
Bowden cable – has a steel layer made from a strip wound into a spiral to make a tube. When you cut it you have to make sure the
end of the strip is not folded over the hole. Indexed derailers need a special kind of outer-cable
– sometimes called SIS cable, SIS stands for Shimano Indexed System – that doesn’t
compress and transmits power precisely. The steel layer of this cable is made of longitudinal
rods. SIS cable always needs ferrules, caps that fit on the cut ends and hold the rods
together. Outer bike cables have a plastic lining that
is crushed when you cut the cable. Use a metal spike to re-open the ends after you’ve cut.
An old Biro is ideal. When the bike cable runs in a straight line
it’s possible to stop the outer-cable, with a stop on the frame, and transmit the pushing
force through the frame.