# Shimano 10-Speed Rear Shifting Driving Me Crazy



## allenpg (Sep 13, 2006)

I'm having a problem with the Shimano 10-speed drivetrain (7800) on my wife's carbon Trek 5000 road bike. The rear derailleur is not shifting smoothly and skipping gears. Here's what I've tried so far:

-New cable (problem still exists)
-Different rear derailleur (7800 and 6600, problem still exists)
-Checked rear dropout alignment with Park Tool (problem still exists)
-Different rear wheel and cassette (problem still exists)
-Chain wear seems OK (less than <1%)
-Limit screws (problem still exists)
-Cable tension (problem still exists)

I think it could be either the housing or chainline. The shifters seem to pull correct cable amount OK. Any thoughts or am I missing something?

Thanks!
-Pete


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## bike981 (Sep 14, 2010)

Does the problem occur on the repair stand, or only when she's actually riding?

Have you checked the front derailleur and chainrings to make sure they are not bent, mis-adjusted, or otherwise interfering with the chain's movement?

Last, in case you haven't already done so, you can look at Shimano's technical documentation here: Shimano. Find the docs for the rear derailleur; it will describe how to adjust it.


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## Dereck (Jan 31, 2005)

Hi Pete
Advice above is solid - go get Shimano's service/fitting doc - it's only a sheet or two - then follow it line by line from the beginning. Then file it if you need it some more!

Have found the ideal set-up to include having all screw adjusters connected with the cable length screwed in to solid zero - do not mess with them unless needed, say while on a ride. It's too easy to get away from the ideal setting and never be able to twiddle those cable length adjusters to what's really needed. At zero, they work. Once your new cables have settled in, re-set if needed and you should be able to leave them be.

Boring, yes, but works every time for me.

Keeping wife's bike in line can be the hardest!

D


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## FBinNY (Jan 24, 2009)

What - *exactly* - is the problem?

Unless you identify, and classify the problem, you can't diagnose it properly and will be left spending money replacing stuff willy nilly until you - maybe - solve it.

For example, limit screws only come into play at the innermost and outermost position, and are rarely, if ever involved in funky shifting, so unless the problem is unique to either of those positions, limit screws aren't the issue.

If you give folks here specifics of what's wrong, we might be able to help. Don't say what you did, but what is happening, ie. is it skipping gears when going to larger sprockets or smaller? Always the same gears or sort of random? The more detail you provide the more likely folks can home in on a specific cause.

Without any details, my first guess would be cable friction, especially if it's hesitating on upshifts. Often this causes folks to bias the trim inboard too far to compensate causing skipping in the other direction.

My next guess (blind w/o details) is housing flex and/or binding. Look for any movement in the housings especially in the frame/derailleur loop. If you see movement, either the housing isn't square in the fitting, or there's excess friction causing the housing to squirm, and the wire not to slide smoothly within.

If the problem is mainly with the larger sprockets, check your "B" screw setting. Having the RD too high will cause erratic shifting because the upper pulley is touching the sprocket through the chain, rather than leading the chain onto it.


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## allenpg (Sep 13, 2006)

Thanks for everyone's responses. I pretty much know Shimano derailleurs inside and out (the Shimano tech docs are nice). I'm 90% sure it's something with the housing. The limit screws are perfect. I've tested two derailleurs and even checked the rear derailleur alignment using 2 different wheels. Here's the problem in greater detail:

With chain in smallest sprocket, I'll tension and attach cable to derailleur. The chain will shift into the next sprocket fine, but will jump two sprockets somewhere in the middle as keep shifting into higher gears. By the time I get to the largest sprocket, I have an extra click on the shifter. Then it will skip a few gears somewhere in the middle when I shift back down. Sometimes the chain refuses to go into the smallest sprocket even with the shifter completely out of clicks. The chain will of course drop into the smallest sprocket if I remove the chain from the rear derailleur.

The shifting had been perfect on my wife's bike for several months. I did remove a 0.5mm spacer on the DS of the external bottom bracket sometime in there. I doubt that would cause a problem like this.

Thanks again for everyone's help!


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## MR_GRUMPY (Aug 21, 2002)

I think that Shimano recommends that you center the derailleur on cog #2. (at least that's what I do)


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## dorset darren (Sep 13, 2011)

i had a problem with shifting a while back that drove me half insane. i fitted a gold jockey wheel that was not compatible then switched back, gears were horible for a while. i did not realize that the jockey wheel was directional and i put it back on the wrong direction round.did you clean or strip down the rear mech removing the jockey wheels recently? long shot i know just trying to help


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## Mike T. (Feb 3, 2004)

allenpg said:


> The chain will of course drop into the smallest sprocket if I remove the *cable* from the rear derailleur.


Did I fix that for you?


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## danl1 (Jul 23, 2005)

Out-of-square cable cuts and pinched cuts that weren't opened properly can answer a lot of these sorts of problems. So can a too-short noodle (the housing section at the RD.)

Another source is a cable that was taped to the bars before the cable was tensioned, creating a small gap between the hood and cable that disappears under increased tension.

First check is to disconnect the cable, give it some gentle finger tension, and work the lever. Try that from the RD, under the chainstay, under the downtube, and after you've untaped the bars, if it comes to that. Your fingers will tell you things that your brain cannot.


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## ericm979 (Jun 26, 2005)

Make sure you have the cable clamped correctly on the derailleur. You may have used the alternate 9sp clamping by mistake. Or you may not have the cable in the groove in the deraileur body in the 10sp position. Sometimes you need to turn the bike upside down and really look at the cable clamp.


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## JacksonDodge (Mar 26, 2006)

allenpg said:


> I'm having a problem with the Shimano 10-speed drivetrain (7800) on my wife's carbon Trek 5000 road bike. The rear derailleur is not shifting smoothly and skipping gears. Here's what I've tried so far:
> 
> -New cable (problem still exists)
> -Different rear derailleur (7800 and 6600, problem still exists)
> ...



Try sliding a small piece of plastic tubing over the shifter cable where it makes contact with the metal cable guide that is attached to the BB shell. I keep a stock of Nokon and Gore liners that I use for this. 

That's usually enough to resolve this issue. I usually drip a bit of lubricant in there as well.


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## carbonite (May 30, 2004)

have you checked the derailleur hanger? is it removable/replaceable. i have had them both bent or loose and it causes shifting fits as you would expect. did the bike fall over or get hit/tapped by vehicle in the garage? it doesnt take much. check it out. check mounting screws for snugness. also do you have to chase the adjustment from low to high and visa/versa? that would indicate that something is loose.


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## FBinNY (Jan 24, 2009)

allenpg said:


> . Here's the problem in greater detail:
> 
> With chain in smallest sprocket, I'll tension and attach cable to derailleur. The chain will shift into the next sprocket fine, but will jump two sprockets somewhere in the middle as keep shifting into higher gears. By the time I get to the largest sprocket, I have an extra click on the shifter. Then it will skip a few gears somewhere in the middle when I shift back down. Sometimes the chain refuses to go into the smallest sprocket even with the shifter completely out of clicks. ...
> !


OK if I get you right, the RD travel is too much and it's spanning the 10 sprockets (9 shifts) in 8 clicks. 

The most common cause of that problem is the cable being attached to the wrong side of the pinch bolt. This effectively shortens the lever arm increasing the shift response. Take a look and check that the cable passes to the far side of the pinch bolt.


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## allenpg (Sep 13, 2006)

FBinNY said:


> The most common cause of that problem is the cable being attached to the wrong side of the pinch bolt. This effectively shortens the lever arm increasing the shift response. Take a look and check that the cable passes to the far side of the pinch bolt.


And we have a winner! I figured this out yesterday. I felt like an idiot. I guess I've been working too much on SRAM lately. On the plus side, I faced the bottom bracket shell on my wife's bike and the crank spins better (and further helps justify why I got the tools years ago)!

Thanks again for everyone's help!
-Pete


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## FBinNY (Jan 24, 2009)

I'm glad I was able to help. This thread demonstrates the importance of a detailed & specific description of the problem. Once you provided details it was easy to pin down likely causes, and solutions.


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