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Emergency derailleur repair advice needed

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Emergency derailleur repair advice needed

Old 01-23-09, 09:47 PM
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ManBearPig
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Emergency derailleur repair advice needed

Had my rear derailleur set up w/a new cassette last week. Put about 200 miles on since. The only adjustment I've made was to the barrell adjuster (tension).

Now, I cannot select the smallest TWO cogs nor the largest ONE cog. What could this be??
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Old 01-23-09, 09:55 PM
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High & Low limit screws.

Visit the "Bicycle Mechanics" forum for more info on adjusting them, or

https://www.sheldonbrown.com/derailer-adjustment.html
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Old 01-24-09, 12:54 AM
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The point I probably did not make clear is that the high and low adjustement screws were set perfectly last week -- I had a trusted shop dial in the rear der. Now, 200 miles later, and the above problem occurs. Shifter also seems to stick sometimes, like something is majorly wrong.
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Old 01-24-09, 02:36 AM
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Originally Posted by ManBearPig View Post
The point I probably did not make clear is that the high and low adjustement screws were set perfectly last week -- I had a trusted shop dial in the rear der. Now, 200 miles later, and the above problem occurs. Shifter also seems to stick sometimes, like something is majorly wrong.
Did your derailleur sustain any recent damage, that you know of? If not, then I suspect the problem is indeed your shifters, not your derailleur. The shifter tells the derailleur what to do--it's like the brain, and the derailleur is the muscle. In this case, the message either isn't getting sent or isn't getting through (check that the cable is not damaged and moves through the housing).

You can confirm this by taking off your chain and seeing if you can move your derailleur by hand through the full range of its settings. If it moves freely when you do this, then the problem is the shifter.

The fact that the shifter is sticking sometimes would seem to confirm that it is the problem. If it's an integrated shifter, about all you can do to salvage it is to flush it out with WD40. It might just be gummed up, and that will help. But if it's failing mechanically, you'll need to replace it.

Last edited by simplify; 01-24-09 at 02:42 AM.
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Old 01-24-09, 02:37 AM
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How old are your cables and housing? I don't think it would explain the RD problems, but might be the answer to sticky shifting.
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Old 01-24-09, 11:54 AM
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Originally Posted by lawkd View Post
You can confirm this by taking off your chain and seeing if you can move your derailleur by hand through the full range of its settings. If it moves freely when you do this, then the problem is the shifter.
Actually, I'd just disconnect the derailleur cable and do the same test. It's more difficult to see the exact alignment of the derailleur, but you can certainly spin the cranks slowly, push the derailleur by hand, and see if it will move the chain to reach all of the cassette cogs. If not, play with the limit screws. Or examine the derailleur for obvious damage. If the derailleur will move the chain across the entire cassette, then I'd start looking at the cables, housing, and shifters.

BTW, is the derailleur hanger straight?
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Old 01-24-09, 12:22 PM
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how is this an emergency?
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