I've also never had a chain or cable of any sort break. I think most breaks are some sort of mechanical failure, the mechanic was a failure in setting it up properly.
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Il faut de l'audace, encore de l'audace, toujours de l'audace
1980 3Rensho-- 1975 Raleigh Sprite 3spd
1990s Raleigh M20 MTB--2007 Windsor Hour (track)
1988 Ducati 750 F1