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Bassworm ®
From WikiPedalia
A form of "helper spring" for rear derailers. This is a fitting which slips over the rear derailer cable just in front of where it disappears into the final loop of housing that leads to the derailer. It includes a length of rubber tubing. The cable runs down the middle of this tubing, and a setscrew clamps one end of the tubing to the cable. This serves two purposes:
- It completely seals this vulnerable entry point against schmutz thrown up by the front tire.
- The rubber tubing acts as a "helper spring" to retract the cable smartly when upshifting. This can provide better upshifting on any bicycle which upshifts sluggishly due to excessive friction or a derailer with a weak spring.
