I was tinkering on an old Enik Roadbike (see here: Convert old road bike to comfortable commuter). Most of the parts were still working fine, but the Positron II was not in a good shape, so I bought a "new" one from ebay. This did work reasonably good for about a year now, but the bike was not moved too much during that time. Now again I'm having problems with the replaced Positron II.

While I was searching for a way to fix it, I found a few posts online where people were mentioning that the Positron is not a good derailleur and they woud recommand to replace it - but no recommendation of what a good replacement for the Positron II would be.

  • Is it possible to replace the Positron II with a more modern, reliable gaer shift?
  • What would be a good replacement for a reasonable price?
  • And how much efford would that be?
  • 1
    Looking online, the Shimano Positron II appears to be a fairly generic BSO-quality derailer. I would think that any standard "ten speed" indexed derailer could be substituted. Commented Jun 11, 2017 at 13:52

1 Answer 1


Positron doesn't have return spring but instead uses single wire for pushing and pulling. That means you have to replace the cable and shift lever, too.

The photo shows that the bike has claw mount derailleur. The best bet is to get a cheap claw mount derailleur and non-indexed shiter.

  • Thanks for your answer - would you have a recommendation regarding the cheap claw mount derailleur?
    – DIF
    Commented Jun 12, 2017 at 7:50
  • Generally we don't do product recommendations, since they depend on what's available in your location and go out of date fast. Ask in local bike shops or do some web searching.
    – ojs
    Commented Jun 12, 2017 at 19:17

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