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Rear Derailleur Question ...

Old 01-29-12, 08:03 AM
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s5fskzfv
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Rear Derailleur Question ...

Hi,

A few weeks ago I asked about adjusting a rear dérailleur with indexed shifting. Someone posted a link to on-line instructions and I went through those and got it adjusted right... I think... The only problem is that sometimes it derails off the high gear. But, I'm 99% sure I have the limit adjustments set right.

It doesn't happen very often, but I think it might occur when I shift through too many gears too quickly or shift more than one gear at a time. Like if I reach the top of a hill and start pedaling rapidly at the crest and start accelerating down the hill and shift from say 3'rd to 6'th on a 7 speed cassette?

Is that a possible explanation? Is it normal to have to shift up methodically one gear at a time or risk derailing off the highest gear? If so, is this a problem that is unique to indexed shifting? I don't remember having this problem as a teenager in the 1970's with my ten speed which didn't have indexed shifting.

Thanks
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Old 01-29-12, 08:35 AM
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dsbrantjr
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s5fskzfv: It is not normal. Try tightening your high limit screw in 1/8 turn increments until the upshift to the small cog shift just hesistates a little bit, then take out the last 1/8 turn. The derailleur should then shift crisply without spilling the chain. A properly-functioning system should not dump the chain regardles of how you move the lever. If you have to leave the high limit adjustment loose to compensate for friction in the derailleur or cabling you will need to address that problem.
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Old 01-29-12, 08:54 AM
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possibles,check wear on jockey pulleys,go to lbs if hanger looks out of line {from the rear jockey pulleys are in alignment vertically and lateral**lbs have alignment tools
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Old 01-29-12, 08:58 AM
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Originally Posted by dsbrantjr View Post
s5fskzfv: It is not normal. Try tightening your high limit screw in 1/8 turn increments until the upshift to the small cog shift just hesistates a little bit, then take out the last 1/8 turn. The derailleur should then shift crisply without spilling the chain. A properly-functioning system should not dump the chain regardles of how you move the lever. If you have to leave the high limit adjustment loose to compensate for friction in the derailleur or cabling you will need to address that problem.
+1. I also believe you do not have the high limit screw adjusted properly and very small incremental turns, the recommended 1/8 of a turn at a time, will make a noticable difference and should make it shift properly.

I set my limit screws with the cable disconnected and shift the derailleur by hand while turning the crank. I will adjust them until I can reach both extreme cogs but have no spillage no matter how fast I let it shift all the way across the cassette.

Last edited by HillRider; 01-29-12 at 09:40 AM.
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Old 01-29-12, 09:34 AM
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s5fskzfv: Try shifiting the derilleur by tugging on the shift wire as directed in this procedure: https://www.parktool.com/blog/repair-...nts-derailleur
Pushing it by hand will not account for friction in the lower cable housing loop, which is common, nor for "slop" in the derailleur linkage. You also won't have to concern yourself with getting your hand caught in the chain and can better concentrate on the adjustments.
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Old 01-29-12, 09:44 AM
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Originally Posted by dsbrantjr View Post
Pushing it by hand will not account for friction in the lower cable housing loop, which is common, nor for "slop" in the derailleur linkage. You also won't have to concern yourself with getting your hand caught in the chain and can better concentrate on the adjustments.
Friction in the cables won't effect the travel limits if they are set too wide, only if they are set too tight and you aren't sure if the chain won't reach the extreme cogs because of the limit screws or cable friction. And, yes you do have to be conscious of where your fingers are when the crank is turning.
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Old 01-29-12, 06:46 PM
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Again, the adjustment is off, but it maybe because of another problem. I set my high limit by placing the bike in the second highest and tighting the stop too tight (so the chain will not shift onto the high gear cog. Next I turn the crank and incrementally loosen the stop screw until the chain drops onto the high gear). If you do this, but the derailleur will not shift the chain to second with one click, then your derailleur is probably worn or out of alinement. When your done you should also check the position of the jockey wheel (from behind the bike) in relation to the high cog. If it looks like the cog has overshot the cog in order to get it to shift, then something in your drive train is probably worn out.
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