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Hello guys, The rear derailleur (6 speed) on my bike (picture attached) shattered all of a sudden while biking uphill after a few months of problems with the chain not fitting immediately on the cassette when I shift gears.

The derailleur's mark is Simplex (made in France). Could you please guide me as to whether I should replace it with a Simplex or can I go with Shimano or something else? what are the characteristics I should be looking for when buying the new derailleur.

Thank you for getting back to me and for taking into account that I am a first-time bike owner (no experience in parts and repairs)



  • Do you value originality ? A similar mech would be ideal, but sourcing one new may be expensive. You should probably consider changing the chain, and maybe time for a new rear cassette as well. If your replacement RD mech is used, make sure its not bent. Loverly bike, btw!
    – Criggie
    Apr 11, 2016 at 22:55

1 Answer 1


If you have friction shifters, they don't really care what kind of rear derailleur you put on them -- just that they can pull enough cable to move the rear derailleur from the highest gear to the lowest gear.

If you're not concerned with having a matching vintage set, I'd suggest pop picking up something like a Shimano Altus or Acera rear derailleur.

But you may want to have the bike checked out by a bike shop -- when a rear derailleur goes, it may bend the mount on the frame (easily straightened with a tool bike shops have) and if it hits the spokes of the rear wheel, it may de-tension or damage some of them (this can be a bit more annoying).

  • Slight tangent: you mention "friction shifters," and I get what kind you mean by that - but what other kinds are there?
    – Jules
    Apr 12, 2016 at 2:41
  • 1
    @JulesMazur index shifters. Ideally they click right into position, one "click" per gear — but only if they're correctly matched to the derailleur and cassette to get the proper amount of cable motion between gears.
    – hobbs
    Apr 12, 2016 at 4:10
  • 1
    Friction shifters are ones which you can move the shift lever continuously and get continuous movement of the rear derailleur.
    – Batman
    Apr 12, 2016 at 4:57
  • Micro-click shifters were available for some time. They are similar to friction shifter but instead of continuous motion the lever could be moved by tiny increments making it easier for people to find the correct position. Most indexed down-tube or bar-end shifters have a knob that switches the shifter from indexed to friction.
    – Carel
    Apr 12, 2016 at 16:27

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