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Old 09-20-12, 02:32 PM   #1
PatrickGSR94
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Trouble down-shifting RD in the middle range

Lately I've been having trouble down-shifting (moving to larger cogs) with my Shimano Deore XT 8-sp RD. It's usually in the middle range of gears, from 3 to 6 or so. Sometimes when I move the down-shift lever, the chain will stay on the previous cog and go *tick* *tick* *tick* *tick* *tick* *tick* for a bit and then finally shift to the larger cog. Or sometimes I'll shift back up (chain never moving off the smaller cog), then shift down again and it will go fine.

It doesn't happen all the time. It happens less often than it does not. But when it does it sure is annoying, because I end up losing a LOT of momentum if I'm trying to down shift while going up a hill.

I don't seem to have any problems with the cogs at the end of the range, like 1-2 and 7-8. Any thoughts?
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Old 09-20-12, 03:48 PM   #2
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Inconsistent shifting most commonly means lever to derailleur transmission is not solid, derailleur to frame geometry is incorrect, or there is a wear/play issue in the drive train.

Transmission: Check to make sure that your shift cable is unfrayed and not kinked, that the housing stops are not distorted or bent and that housing is operating smoothly and that none of the inner housing is escaping past the housing ferrules.

Geometry: In all gear combinations when viewing from the rear of the bike, level with the derailleur, the pulley assembly should be vertical (bottom not pointed toward or away from the wheel) and should be aligned parallel to the centerline of the bicycle (not pointed to the left or right). If it is not then either the derailleur hanger is not aligned properly or the derailleur has been twisted out of alignment. It's best with indexed shifting to have the hanger professionally aligned.

Wear/play: If the problem still occurs then it's time to try a derailleur and/or chain swap.
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Old 09-20-12, 11:49 PM   #3
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Took a closer look at it, and the main issues are actually downshifting from 8 (smallest cog) to 7, and from 5 to 4. Other shifting seems to be fine. When in 8 and shifting down to 7, it's like the RD just barely doesn't move over far enough to get the chain onto the next larger cog. If I bump the shift lever just a bit, it will go on and engage. Same with going from 5 to 4. When I looked at it from the rear, it looked like the RD was just barely out of alignment over 7 and 4. But others seem to be okay. It could be out of alignment on all gears, just not enough to cause trouble except 8 to 7 and 5 to 4.
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Old 09-21-12, 05:17 AM   #4
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I should have pointed out that although it's a good idea to eyeball the derailleur for obvious misalignment, you can't always tell for sure. The fact that the problem is mainly when you first put tension on the cable tells me that there could indeed be a cable housing related problem. But again, once you have gone through basic adjustment address the three conditions I listed above in order.
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Old 09-21-12, 07:27 AM   #5
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Did you try adjusting the cable tension? If not, start with tightening 1/2 turn and work from there.
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Old 09-21-12, 07:30 AM   #6
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Have not, will check it out later. I'll probably just take it by the LBS tomorrow anyway since I want to see what they have in the way of road bikes, see if they're running any specials, etc.

Just seems odd that the problem is mainly confined between those two sets of cogs, while downshifting to other cogs 7-6-5 and 4-3-2-1 all seem fine.
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Old 09-21-12, 09:13 AM   #7
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Just seems odd that the problem is mainly confined between those two sets of cogs, while downshifting to other cogs 7-6-5 and 4-3-2-1 all seem fine.
Yes, it's unusual - which is why I noted the specific reasons for inconsistent shifting.
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Old 09-22-12, 09:26 PM   #8
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Took it into the LBS today, turns out the RD shifting troubles just needed a little turn of the barrel adjustor on the RD itself. Quick fix. What took some more work was adjusting the FD to make it stop dropping the chain off the large ring. It's done that a few times in the past several months, but hopefully won't do it anymore. $10 labor, and I also took the opportunity to pick up a second Camelback Podium Chill bottle. Love those things.
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Old 09-23-12, 06:01 AM   #9
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I'm glad it's working well now, but I find it hard to believe that a cable tension adjustment alone could solve the problems you describe. They may have done more than just that. Time will tell, but if the symptoms reoccur I would encourage you to have the hanger alignment checked.
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Old 09-23-12, 06:31 AM   #10
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Nope, the bike was in a repair stand mounted on the sales desk. The guy spun the pedals, downshifted, immediately saw the issue, did about a 1/2 turn on the barrel adjustor on the FD and the problem immediately corrected itself. After that I rode 15 miles around town and had now RD problems whatsoever.
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Old 09-23-12, 06:57 AM   #11
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Great, glad it worked. Also very reasonable labor charge for adjusting both front and rear, even if only minor.
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Old 09-25-12, 05:55 AM   #12
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Quote:
Originally Posted by PatrickGSR94 View Post
Took it into the LBS today, turns out the RD shifting troubles just needed a little turn of the barrel adjustor on the RD itself. Quick fix. What took some more work was adjusting the FD to make it stop dropping the chain off the large ring.
Great, a simple adj as I suspected for the rear. FDs can be a bit more challenging to cure because of the varying shapes, short chainstays, as well as ability to mount them at an angle. There's a bit more finesse involved. Glad you got it fixed.
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