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I have this old bike that I'm taking a look at (ie oiling and whatnot) for a friend. The bike is old (maybe 20 years old), with this type of a gear shifter for front derailleur:

One lever shifter

It has a single lever/handle thing that looks like it should slide around to switch the gears.

Could anyone tell me what type this is? I need to fix it (because it doesn't shift), but I'm not sure how to approach it exactly...

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    Welcome to Bicycles @Mewa. An image of the gears would probably help you get accurate answers. – andy256 Aug 21 '15 at 4:44
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    Looks like a bog-standard friction shifter to me. The knob on top adjusts the degree of friction. If the friction's right, the cable moves freely, and the derailer is properly adjusted, it just works. – Daniel R Hicks Aug 21 '15 at 12:30
  • @DanielRHicks, thanks! I took out the knob on the top completely and it still doesn't shift, so I feel like it's maybe the cable getting caught on something. I am planning to disconnect the cable from the shifter and see if it shifts around then. – Mewa Aug 21 '15 at 16:53
  • What do you mean by "doesn't shift"? The knob just affects how hard it is to move the lever. There is a cable from the shifter to the derailer. That cable should be tight, except perhaps when the lever is pushed all the way to one end, corresponding to "first gear" on the front sprockets. When you move the lever the cable should move and that should move the derailer. It's all out in the open to see, and hence easy to diagnose, if you simply study it a bit. – Daniel R Hicks Aug 21 '15 at 18:05
  • (If the bike has been neglected a bit the most likely problem is a rusted up cable housing, keeping the cable from moving.) – Daniel R Hicks Aug 21 '15 at 18:07
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I'd call it a thumb shiifter. Guess its for the front derailleur, and on a bike that old its probably not indexed, which makes this easier.

Firstly is the gear wire loose? Check them down on the frame and see if they're slack. If so, the wire has snapped or the end has come off inside the shifter.

If you can't physically move the shifter then it could be jammed with wire or the "barrel", or just plain rusted.

That plastic bit on top is a handle- its the top of the tension screw. If you undo it completely you'll be able to see into the mechanism for rust. This is also how you'd get access to the cable to replace it. Note your other-hand shifter is more likely to be indexed (ie click-stops at every gear position) so not directly comparable.

If the problem is rust, tell your friend to stop storing the bike outside. If its a broken cable, that's a fairly straightforward fix, albeit dirty.

  • It sure isn't indexed :) The gear wire feels tight. I can push the shifter a little bit (on a circle this is about 20 degrees I would guess), and I can see it try to move the derailleur, but nowhere near enough to shift the gears. The bike itself is actually in great condition - there is very very little rust on the frame, or other components, and I think she stores it indoors. – Mewa Aug 21 '15 at 16:58
  • I took the tension screw out and it looks nice and shiny inside. Since even without the tension screw I still can't move the shifter past the 20 degrees (and it tends to spring back to its original position), I feel like maybe the cable is getting caught on something within the tubing? Maybe in the region where it goes around the bottom bracket. – Mewa Aug 21 '15 at 16:58
  • I'm thinking of just disconnecting the cable from the shifter and trying to isolate the problem - if it shifts without the cable then I guess it's the cable. if it still doesn't move much, then it's the shifter. Does that seem like a good approach? – Mewa Aug 21 '15 at 16:59

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