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Rear derailleur fine adjustment

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Rear derailleur fine adjustment

Old 04-13-09, 06:47 PM
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Rear derailleur fine adjustment

Hey all - it's been a long time since I've posted here, but could use some help.

I've been futzing with the indexing of my rear derailleur for a while now, and just can't seem to get it right. It seems impossible to find the balance between enough cable tension to pull the chain onto larger cogs quickly and reliably while allowing the return spring enough tension to pull it back down. I've followed adjustment walk-throughs from sheldon, parktools.com and a book that I've got on bike maintenance and I'm just not getting the performance I want. Btw, this is an Ultegra 10-speed derailleur with 105 shifters.

Everything is very clean - I've even gone so far as to disassemble the cage to remove the pulleys for cleaning. Cables are pretty new and have recently been lubed with penetrating oil. There is the possibility that I bent the derailleur hanger a while back but I've checked the alignment (as well as possible without a proper gauge, anyway) and it seems fine. I'm planning on stopping by my LBS tomorrow, but if I could figure this out with your help that would be fantastic.

Any suggestions? Is there something obvious I may be missing? Thanks in advance for any help!
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Old 04-13-09, 10:07 PM
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I run into bikes that are like that once in awhile. First thing I would do is release all the tension so the derailer returns to the smallest gear by shifting all the way up(?). Then, release the cable clamp so the cable is free. Then tighten the cable barrel adjuster on the derailer all the way in, then back it out 2 full turns. Now tighten or loosen the screw that sets how far down the derailer can go without any cable tension, you want the derailer to line up perfectly with the smallest gear. Pedal a few times (best done with the bike upside down). pay close attention to how the chain lays onto the gear and make sure it is right where you want it, in the center. After you have made that adjustment, pull the cable tight and fasten it down. Now use the cable barrel adjuster to pull the rest of the slack out of the cable. Back it out until the derailer starts to move, then back off just slightly.

If that is what you already did and it is still giving you problems try this. shift the derailer to the middle gear. Look at where it is laying down on the gear, if it is not directly centered, use the cable barrel adjuster to bring it slightly one way or the other. Then try shifting through all the gears again.

The last thing to check is the adjuster that butts onto the rear derailer hanger on the frame drop out. Adjust it so that the jockey pully is fairly close to the cogs as it shifts up and down. It will help give you a little crisper shifting.

If that doesnt do it... I'm not sure what will. Good luck PM me if you still cant get it.
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Old 04-13-09, 10:31 PM
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Get a bike shop to check the derailleur hanger alignment. If the RD has taken a knock the whole thing may be out of square.

Straightening out can make a huge difference to shifting. I was in the same position as the OP, after a fall that knocked the RD, a quarter of a turn more tension on the cable and it wouldn't shift down properly, quarter of a turn less and it wouldn't shift up. A new derailleur hanger (which I still had to align) fixed the problem.

You can buy or make yourself an alignment tool but the simplest way is to get the LBS to do it for $10 or so.
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Old 04-13-09, 11:57 PM
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+1 on scirocco's comment to have the hanger alignment checked. All bets are off if the hanger alignment is off and you waste the time fiddling with an unresolvable situation. Once the hanger is aligned so it is in the same plane as the wheel or bike centerline then follow the proper RD adjustments and if the shifter indexing is proper for the derailer you have it should be able to shift quickly both up and down at your command. And that's a good thing!
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Old 04-14-09, 01:01 AM
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burtonridr, I'm following your advice the next time I struggle with a RD. I spent a lot of time debugging my son's the last few days. Thx for the detailed explanation. I went through some of the steps, hoping for a quick resolution, but I think your methodical approach will pay for itself in reduced time and frustration.

One thing I had attributed to the RD (and almost bought a new one!) was a catch every so often as the chain went through the pulleys. Turned out is was a stiff link.

Last edited by sunburst; 04-14-09 at 01:04 AM.
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Old 04-14-09, 06:48 AM
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In addition to the chance of a misaligned RD, cable housing friction can make it impossible to get achieve proper shifting. If you get the shifting to work properly going to larger cogs, but the shifts to smaller cogs hesitate, it's usually a cable friction problem.
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Old 04-14-09, 06:54 AM
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I removed the cable from the clamp on my rear Campagnolo derailleur, and then later reinstalled it on the wrong side of the clamp. I couldn't get both the large and small cogs to center at the same time, since the pull angle was wrong. It took a while to figure that one out. Maybe you have a similar problem--did you remove the cable at some point?

EDIT--Is the chain centered on both the large and small cogs, but it doesn't drop to the next smallest cog consistently?

Last edited by rm -rf; 04-14-09 at 06:58 AM.
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Old 04-14-09, 08:40 AM
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Thanks for all of the replies, good advice from everyone. I've gotten the indexing pretty close, but I still think it should be snappier; I have another bike with 12-year-old Ultegra derailleurs, and it's great - I think this 2-year-old stuff should work just as well.

I haven't replace the cable or housing near the derailleur, but that did cross my mind. The bike was well maintained by my father (who has since given it to me) so I assume the cables are in good shape, but who knows. That loop does seem a bit small, so that could be part of the problem.

I'm heading the the shop today to have the hanger alignment checked. It looks alright when I eyeball it, but that's obviously not a scientific measurement.

burtonrdr- your advice to start in the middle and work out is good. I ended up trying that last night, and was able to get things closer than ever.

scirocco- do you have a resource which details making your own alignment tool?

rm -rf - the pull angle is as it should be, but who knows, trying a different angle may help. I'll give it a shot. and yes, the high/low stops are set correctly (centered on the small and large cogs) and I can adjust cable tension to pull up to the next largest cog consistently, but dropping to smaller cogs is sluggish and unpredictable.

thanks a ton guys!
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