This is a brake cable for a road bike. As you can see, it’s not in the best of conditions. A brand new brake cable is shiny and clean, with none of the corrosion and dirt this rolled-up length has picked up in its service life.
With more corrosion and dirt in the cable, more friction develops between it and the cable housing. You’ll feel this dragging sensation on your fingertips as you squeeze the brake levers, a reminder that things aren’t running as smooth as they should be.
This will happen to all your cables and their housings, too. It’s not a matter of if, but when. Riding in poor conditions tends to speed up their deterioration, but if your frame supports a full run of cable housing for the inner cables, that will keep contaminants at bay.
This is a shift or gear cable that has become frayed inside a right-side STI lever. You can see the individual filaments of the cable separating, curling, pointing every other way — except straight into the shifting mechanism. When this happens, you lose the use of a fair number of cogs on your cassette. Pushing the shift lever to the lost cogs, you may hear a click, but you don’t feel the weight of the shift behind the lever.
It’s also fairly annoying to fish out the frayed shift cable…
…Especially when some of it is left inside the control lever body. What a squiggly mess.
Apart from chain cleaning and lubrication, brake and shift cable and housing replacement is the foremost periodic maintenance job on a bicycle. It’s pretty cheap, too. Get on top of it once or twice a year so your bike performs as best as it can.
It’s still a long way off before maintenance-reducing technologies like electronic gear shifting, hydraulic gear shifting, and hydraulic braking are cheap enough for the average rider to afford.