How do you tension a front derailleur cable? (video)
How do you fix a derailleur cable? (video)
How do you cut a shifter cable without fraying?
Wrap a piece of clear tape around the cable, cut with your favorite cutter. No frayed ends, tape keeps everything in place. via
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How often should I change my derailleur?
Derailleurs will last almost indefinitely. The jockey wheels will wear out in time (tens of thousands of km) but the rest of the mechanism shouldn't see significant wear. It could be that the spring will break at some point due to material fatigue, but that is also a relatively easy to replace part on most derailleurs. via