I have very few complaints with my BSO, but this is one of them.

My rear derailleur seems to hold the same 'up and down' tension across all the cogs. So when I'm on the first couple of cogs (32 and 26 teeth), the shifting is precise and efficient. But when I move out towards the end of the freewheel, I have to push the lever a long way to make the jump to the next cog, and then pull it back to keep it from making noise.

Basically, the top jockey wheel stays at the same height all the way across the freewheel, which means that when it's on the small cogs, it's hanging well below them, and has to move a long way to get the chain to hop to the next cog.

Is there a way to adjust this, or is it simply a consequence of having BSO-level components?

  • Is this a friction shifter (vs "indexed")? Also, what front ring are you on when you're trying this? – Daniel R Hicks Oct 29 '16 at 22:05
  • The top jockey wheel should move diagonally, when viewed from the rear of the bike. Are you saying it moves horizontally only ? – Criggie Oct 29 '16 at 22:41
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    @DanielRHicks I use the small cogs generally with a 48 ring, sometimes a 38. Yes, it is a friction shifter. – BSO rider Oct 30 '16 at 14:08
  • The issue is more left vs right rather than the number of teeth. If you "cross chain" -- run small-small or large-large so that the chain is not "square" with the crank and axle -- you tend to have more problems with chatter and shifting. – Daniel R Hicks Oct 30 '16 at 14:13
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    @Criggie It move slightly diagonally, but not much. When it's on the smallest cog (14t), there's probably a 3cm gap between the cog and jockey wheel – BSO rider Oct 30 '16 at 14:22

OK Based on comments - your BSO rear derailler is not following the contour of your cassette, and is ending up a long way from the smaller cog.

It should be like this stylised image:

enter image description here

Doubtless you have some wear on the cassette, and the RD position is limiting the number of teeth that are actively engaged in the chain.

I bet on the big cog you've got 5/8 of the teeth meshed with the chain (~20 teeth) and on the little 14 you might have as few as 3/8 (~5 teeth) so this accelerates wear, and fewer teeth meshed means skipping errors earlier.

You could try a new cassette and chain, if the cassette appears worn.

The other option would be check the rear derailler and see if you can make it move more diagonally

Another possibility is that your B-tension screw is too loose, or isn't even there.

  • This really isn't helpful. I see your point about it accelerating wear, but that's not my issue. I want to know if there's a way to adjust the derailler so it doesn't do this. – BSO rider Oct 31 '16 at 0:26
  • Accelerated wear might be exactly the cause for your sloppy shifting. Was it like this from new? You could try twiddling the B tension screw if its adjustable. Otherwise it might be time for a better rear derailer mechanism. Given the space between the jockey wheel and the smaller cogs, you might also have wear or sloppiness in the jockey wheel itself. – Criggie Oct 31 '16 at 1:55
  • Ahhhh... the B tension screw. I had forgotten about that, because my bike doesn't even have one. Oops. I guess that's my problem. – BSO rider Oct 31 '16 at 11:58

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