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Old 05-13-12, 09:23 AM   #1
lungimsam
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Rear derailer out of whack after barrel adjustment - please advise.

Hi everyone,

On my way home yesterday the rear derailer gears started shifting badly (minor hesitations, noisy). So I figured I would tighten the cable at the rear derailer by turning the adjuster barrel counter-clockwise a half turn. I did it. Made it a little worse, so I turned it back...and before you know it, I can't remember how to get the adjuster barrel back to the original position I started from, though the gearing seems to be better now, but still not how it usually is.

Any advice on how to get the gearing smooth again?

Also, I notice my derailer wiggles ever so slightly on the mount at the frame (~ 16th inch at the mount point), even though the derailer mounting bolt is tightend all the way. Is it supposed to wiggle a little even though it is bolted down tight?

I have a Shimano Sora on my road bike, and the chain is still ok.

Thanks so much for any help.

Last edited by lungimsam; 05-13-12 at 09:40 AM.
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Old 05-13-12, 09:42 AM   #2
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Did something else happen to the bike? Was the bike dropped or did another bike fall against it? Did you run something over? Look closely where it mounts, where you see looseness. Does anything look cracked? Check your cable for fraying, especially in your shifters. If the cable is frayed at the shifter you will save a lot of heartache if you replace it before it breaks. It is unusual for a bike to just start shifting badly out of the blue. If you have ruled out sudden damage, then go through the derailleur adjustment procedure shown here: http://www.parktool.com/blog/repair-...nts-derailleur
Start at the beginning and go step by step. If the desired result cannot be achieved at a step, stop and find out why before going to the next. Be systematic, just making adjustments willy-nilly without understanding what you are trying to achieve will only get you into trouble.
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Old 05-13-12, 11:19 AM   #3
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^^^ What he said ^^^

It'll probably just be easier to adjust it from scratch. It's really not that hard and quite satisfying. Just read the link as suggested, have a little bit of time and some patience and it'll be oh so nice...
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Old 05-13-12, 01:01 PM   #4
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Thanks, I'll check it out.

Didn't see any fraying or breaks when I inspected it. So hopefully just needs tweaking.
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Old 05-13-12, 02:35 PM   #5
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Originally Posted by dsbrantjr View Post
Did something else happen to the bike? Was the bike dropped or did another bike fall against it? .... .
Take this to heart, and check everything but especially the inner limit screw setting, before simply correcting the trim.

Gear cables don't shrink, so if the RD is suddenly out of trim, especially if now trimmed too far in, it's almost certainly because the hanger (or RD, though less likely) is bent inward a bit, probably from an impact. You can correct the trim with the adjusting barrel, but since the entire RD is now farther in than before both limit screws will be off. Ignoring this can lead to over-shifting the chain or RD into the spokes, with nasty, expensive consequences.

The best test for the inner limit screw is to shift the RD as far in as possible by pulling the bare wire away from the frame like a bow string. Do this off the bike while pedaling slowly with the wheel off the floor. Adjust the limit to the tightest setting that still allows you to shift to low crisply from the adjacent sprocket.

Now set the trim on the second or third to outer sprocket (not the outermost), by putting the lever in the corresponding position and centering the RD so it runs quietly. Then fine tuning so you can shift in either direction smoothly. Finally, adjust the outer limit so you can shift to high from the next sprocket smoothly, and the chain runs quietly i high.
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Old 05-13-12, 11:52 PM   #6
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Originally Posted by lungimsam View Post
Also, I notice my derailer wiggles ever so slightly on the mount at the frame (~ 16th inch at the mount point), even though the derailer mounting bolt is tightend all the way. Is it supposed to wiggle a little even though it is bolted down tight?
This is far more common than it should be, but I suspect it doesn't have a whole lot of impact.

But it certainly can't help. If you want to do everything possible to improve your shifting, you can disassemble the pivot and find/make/modify a washer to go under the circlip. Shouldn't matter if the pivot is slightly stiff.

I find myself eventually doing this to just about every derailleur I use, including Campy Veloce and Shimano 600.
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