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Indexing Slipping

Old 07-31-20, 01:30 PM
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Pratt
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Indexing Slipping

Before I threaten an innocent bike with screw drivers, wrenches, hammers, and other implements of destruction, I thought I would ask a little advice. My 1992 vintage bike with Sun Tour 7 speed XC Comp derailleur, with bar end sifter, indexes less than perfectly. I have to over shift little ,or a lot, to make all the parts happy and quiet. So, what adjustments should I contemplate? If I take the shifter apart can I adjust it, or convert it to friction. Since I am already adjusting shifts, friction would be no terrible sacrifice.
Thanks in advance
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Old 07-31-20, 03:17 PM
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dsbrantjr
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Put the hammer down and step away from it. Well, most shifters and/or derailleurs have barrel adjusters to tweak the indexing. Maybe try adjusting them.
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Old 07-31-20, 04:09 PM
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andrewclaus
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Or you could have some friction in the cable system. Pull apart, clean, inspect and lubricate if adjustment doesn't clear it up.
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Old 07-31-20, 06:23 PM
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Ball in detent indexed levers will tend to have the detent grow and thus the overshift grow. Until this frustrates you enough to do something about why change? Is it at that point yet? Only you can answer this. Andy
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Old 07-31-20, 06:26 PM
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Moe Zhoost
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Squirt some light lube into the shifter and work it a bit. It's probably gummed up to the point that the indexing detents are not engaging well. If the lube doesn't help, perhaps it's just worn out.

One thing that I find necessary in diagnosing an indexed shifter is to disconnect the cable from the derailleur and pull it out of the housing. Then, holding hand tension on the cable, I'll run the shifter through it's range. If you feel incremental positive cable movements with no slipping, your problem may be elsewhere..
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Old 08-01-20, 01:41 PM
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Have you MEASURED the chain?

How fresh are the cables and housings?
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Old 08-01-20, 06:17 PM
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Pratt
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Chain has <200 miles on it, cables and housings are original ~30 yo
De-gumming the shifter sounds like a good start.
Thanks, all
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