Control cables have two elements, a wound steel wire inner-cable with a metal nipple at one end, and a flexible tubular outer-cable that the inner-cable runs through.
Bike cable nipples
Different hand controls use bike cables with differently shaped nipples.
Outer bike cable has three layers an exterior plastic sheath to protect the cable, a steel layer that gives the cable it’s strength, a plastic tube inside the steel layer that the inner cable runs in.
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.
Cutting Brake Outer-cable
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. Modern bikes often have slots in the cable stops so the cable can be dismounted(link) for inspection, cleaning and lubrication, without unclamping the inner-wire.
The inner bike cables come in standard lengths that are long enough for all normal uses. You may need to get extra-long cables for tandems or other special cycles. Once intalled you cut off the excess length then cap the end with a soft metal end-cap that is crimped in place with pliers. The end-cap stops the wire from fraying.