I bought a basic wheel set for a hack bike project. The rear wheel has a single speed cog, and a dangly adjuster thingy - maybe 2 inches long. What is that for?

  • 5
    Could you perhaps include a picture or a link to something similar? Dec 3, 2012 at 10:58
  • 4
    This really needs a picture or a more detailed description. There are several things that could conceivably be dangling back there...
    – freiheit
    Dec 3, 2012 at 17:57
  • Hi Guys, ill add a photo tonight when i get home from work. Thanks for pitching in. It is definitely not a internal hub or coaster brake.
    – Will
    Dec 3, 2012 at 22:02
  • Given that it is a single speed, it could be a chain tensioner. But as the other commenters have said, a picture would help.
    – deemar
    Dec 6, 2012 at 11:03

2 Answers 2


The dangly adjuster thing is most likely the toggle chain for an internally geared hub!

3 speed hub

The tension on that chain shifts the hub internally (rather than through a derailleur and cogset). Bike hacks with three-speed hubs are quite common, but get very complicated. Here is some information on Sturmey Archer hubs courtesy of Sheldon Brown.

Below is a picture of the toggle chain and rod which is attached to the inside of the hub. Good luck!

enter image description here

  • Also, an alternative to @Tom77's suggestion of a coaster brake, it could also be a drum brake which will have a reaction arm and an actuation arm. They can be installed on front or rear hubs and are frequently cable actuated (as opposed to a coaster brake's pedal-actuation.)
    – WTHarper
    Dec 3, 2012 at 19:13

It sounds like you have a coaster brake (operated by pedalling backwards), if this is the case then the dangly thing is the reaction arm.

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