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Old 08-21-07, 09:01 AM   #1
Novakane 
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Bio-Pace & 200 GS Shimano Not Derailing Correctly

I recently was given a very nice Miele Mercury mountain bike. I'm fairly new to indexed shifters, and I'm having a bit of an issue with shifting on this bike which I cannot immediately see the solution to.

I did some work on the weekend to get it up to ride-able condition (replaced brake pads, cleaned and lubed the drive-train, etc.) and noticed that the derailer would not move inside enough to drop the chain onto the smallest cog. When riding it home from picking it up, I also had the chain drop off the outside of the large cog once or twice while testing the shifters, and it would not shift into the largest cog on the wheel.
I started by adjusting the rear derailer stops to allow it onto the bigger ring, that was pretty basic - problem solved for the rear, shifts great now.

I then addressed the chain-jump issue by adjusting the appropriate screw to stop it from pushing the chain so far off the cogs. I tried to shift to the small cog to make adjustments for that stop - it wouldn't. It stopped at the middle one. Checked the screw - not even touching yet, so it's not stopping the derailer. Shifted to the big ring, OK, clicked the shifter back again, middle cog. Further clicks in that direction have no effect, the derailer just doesn't want to go that far inside.

I checked the mechanism, and it looks like that's as far inside as it wants to go. My first instinct was to just ignore the problem - I live in the suburbs, the biggest hill I can find can be tackled with the middle cog and using one of the larger ones in the back. Oops, now the chain drops onto the small cog all on it's own under a load, randomly, if the rear is on an inner ring as well.

There's something about a self-shifting chain that won't allow itself to be ignored, so I appeal to the gurus of bikedom - what's happening here? Please let me know if you need further details - I can't post a photo as my brother has my digital camera for a while.

My thoughts are that maybe the derailer has been bent outwards? It doesn't appear damaged, and I hesitate to muscle it inwards if that's not really the issue. What leads me to this thinking is that it won't shift inwards and originally had a problem of shifting too far outwards, but since this is an indexed shifter and not a manual one I suspect there's an adjustment to be made elsewhere that I'm missing.
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Old 08-21-07, 10:09 AM   #2
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You may have a bad shift cable that’s binding when trying to go to the smallest chain ring. It could also be the derailleur is binding due to rust as it sounds like no one ever shifted to that small chain ring. I would disconnect the cable from the shifter and work the shifter manually and pull the cable back and forth in the casings to check for binding. It could also be the shifter. Grip and trigger shifters need to be cleaned and lubed from time to time. I picked up a Specialized Hybrid with the same drive train and most likely shifters as yours and I immediately noticed the shifters were binding up preventing proper operation. I removed the covers to clean and lube them and install new cables and found a wasp had build a mud nest inside them.
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Old 08-21-07, 10:28 AM   #3
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I did consider the cable/shifter aspect as a possibility. Next step - figure out how to open the casing on a 200GS shifter. Last time I tried adjusting an indexed shifter I managed to snap the bolt right off in the thread.
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Old 08-21-07, 10:36 AM   #4
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Follow the dérailleur adjustment instructions on the Park Tool site, starting from scratch and skipping no steps.
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Old 08-21-07, 10:37 AM   #5
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Quote:
Originally Posted by Novakane View Post
I did consider the cable/shifter aspect as a possibility. Next step - figure out how to open the casing on a 200GS shifter. Last time I tried adjusting an indexed shifter I managed to snap the bolt right off in the thread.
You can't adjust indexed shifters per se but sometimes the barrel adjustment is right at the shifter.

This from Rev. Chuck in the archives: ".. you need to shift to the seventh position (upper button if it is push-push, index finger button if it is push-pull). Look opposite the adjuster (or the stop for the housing if it does not have an adjuster) there should be a hole in the plastic to feed the cable thru. If you cannot see the internal stop for the cable end thru the hole, then it has not been shifted far enough, you need to shift the other way, or the shifter is sticking. (If you don't get a full set of clicks it is sticking and spraying some solvent in there can help)."
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Last edited by DMF; 08-21-07 at 10:42 AM.
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Old 08-21-07, 12:04 PM   #6
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Quote:
Originally Posted by DMF View Post
You can't adjust indexed shifters per se but sometimes the barrel adjustment is right at the shifter.
After reading through the guide on Park Tools, I'm starting to suspect it needs an adjustment with the barrel shifter, but I won't be able to really check until I'm near the bike and not at work.

Thanks for all the tips, hopefully I can get this sorted out.
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