Argh! Ghost shifting is driving me crazy!

[93KgBike]

My 7800 is old, but not sloppy.

Try, barrel adj. full-right-back-1/8 before cable attachment. Then, fully downshift and, using your thumb, press the derailleur out until the lower jockey wheel is in line with the second cog and take-up the cable slack and tighten. When you release, the derailleur should be properly setup over the 11t. Barrel adjust the gears for noise at 2, and may 12 or so?

And check the b-screw setting, larger gears may change the position.

GL

[giordana93]

not sure about your cable routing but make sure (if you have one) that the guide under the bottom bracket isn't loose. and make sure there are no kinks obviously (you prolly did but worth mentioning). couldn't hurt to make sure the last loop into the derailleur gets a drop of tri-flow or similar. sure sounds like the cable is hanging up somewhere or there's a "loose connection" like that guide pivoting or a ferrule not sitting squarely

edit: if all else fails, you might have to unwrap bar tape and make sure the housing is nice and tight going into the shifter, after duly releasing any tape (electrical or other) holding the housing in place under the bar tape

[Matthew]

Perplexing for sure. My 7800 group has over 22k miles and works beautifully. Don't have any suggestions other than what's already been covered. Hopefully you get it fixed. Would be maddening.

[Moorecw]

Does it ghost shift all throughout the cassette or only at certain points on the cassette? Does it happens at one end of the cassette and tunes at the other end. I have seen this happen when the hanger is out of alignment.

[TexasJohn]

Try a different shifter or rebuild / service it. Shifting is one of the five parts, and often gets worn late in life.

[oldpotatoe]

Originally Posted by TexasJohn

Try a different shifter or rebuild / service it. Shifting is one of the five parts, and often gets worn late in life.

Hmm, .no small parts and even if there were, these things machine assembled with all sorts of hidden/blind springs and clips..But give it a try....

[Big Dan]

Same Campagnolo drivel. How does that help?
Keep bringing the same crap to diminish others.
Difficult to take this guy serious.
I'm sure the 7800 RD works fine and the problem is just in the cable or housing.

[oldpotatoe]

Originally Posted by Big Dan

Same Campagnolo drivel. How does that help?
Keep bringing the same crap to diminish others.
Difficult to take this guy serious.
I'm sure the 7800 RD works fine and the problem is just in the cable or housing.

yawn...
same guy gotta slam the Campag fan boy..diffucult to take this guy serious..BUT get to 'diminsh' this guy..like, so what.

It's toys Big, don't take me serious....'kay?

You DO know how to block somebody, yes? If you don't, I can show ya...

[palincss]

I'm sorry, but this should not turn into a Shimano vs Campagnolo pissing contest.

The OP has an X setup, it used to work and now it doesn't. It should be possible to fix it so that it works correctly, the way virtually all such systems work; and that's the information he's after, not whether some other brand is better for whatever obscure or theoretical reason that has nothing whatsoever to do with his current situation.

[TexasJohn]

Originally Posted by oldpotatoe

Hmm, .no small parts and even if there were, these things machine assembled with all sorts of hidden/blind springs and clips..But give it a try....

You are the Jedi bike master, but seems the only thing he has not swapped out is the shifter itself. Worth a try for sure.

[jc031699]

Originally Posted by OtayBW

Maybe I'm missing something here, but if the chain is riding up on a bigger cog (lower gear), then you'd want to loosen the barrel adjuster, no?

Agree with this
If the chain is riding up on the cog that it’s on already, the cable is too tight. If you have the cable adjusters all at “zero” it implies that you can’t decrease cable tension. Is that true? ... being adjusted on the stand is not the same as being adjusted under load and at 90-100 rpm cadence, maybe just needs a click or two looser on the cable adjuster while riding to get just right.

Also, are you sure you are clamping the cable in the right place on the RD cable fixing bolt? Sometimes the little clamp plate rotates around into the wrong position when you have it all apart. This can have a subtle effect on the shift ratio.

https://www.sheldonbrown.com/dura-ace.html




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[bitpuddle]

As mentioned, I’d try a Shimano chain, if possible.

If you rewrapped the bars, make sure there isn’t a funny bend of the housing under the tape causing some binding with the cable. That can mimic tension issues. If you unwrap the bars to the shifters and the issue goes away, something is binding.

If you took off/replaced the cassette, make sure all the spacers are in the right place and that none of the cogs have any play. Remove and reseat if there is any doubt.

[oldpotatoe]

Originally Posted by bitpuddle

As mentioned, I’d try a Shimano chain, if possible.

If you rewrapped the bars, make sure there isn’t a funny bend of the housing under the tape causing some binding with the cable. That can mimic tension issues. If you unwrap the bars to the shifters and the issue goes away, something is binding.

If you took off/replaced the cassette, make sure all the spacers are in the right place and that none of the cogs have any play. Remove and reseat if there is any doubt.

While very true for 7900, 7800(OPs stuff) is exposed der housing...Last point a good one, make sure the 1mm spacer is onto the FHB first for shimano 10s cogsets..and the additional 1.85 one if on a 11s freehub body..

[texbike]

Originally Posted by Dude

are the der cable heads seated properly in the shifter?
Is the rest der cable routed correctly through the shifter?
pop off ferrules and make sure the der housing strands are all even.
reassembled der/jockey wheels incorrectly?
That's not how you set up a rear derailleur.
- rear der barrel adjusters should be about 2/3 of the way screwed in. thread frame barrel adjusters the same amount in so you can use them while riding.
- with no cable tension on rear der, set limit screws. High limit screw unscrew until you hear noise/jumping. screw in until no noise/jumping. - use your hand to push the der to low limit screw repeat limit screw thing.
- install cable. 1 click is one shift yada yada. don't "take slack out of cable" we're talking empirical feedback here, not based on feel.
- once limit screws and cable is set, pull with some pretty good force on teh cables to seat all the housing/ferrules etc.
- readjust cable tension as necessary.

Also, have you tried other *new* cassettes?
Is the b-screw too far in/out?
or you could take it to a shop and have another set of eyes on it.

Originally Posted by Big Dan

Sometimes is good to check the limit screws also.
Put it on the smallest cog and release the cable, check if it stays there or jumps.

Originally Posted by jamesau

Go to shimano site and print out the service instructions:
https://si.shimano.com/#/en/search/S...7800&type=ROAD

Verify derailleur and hanger fixing bolts torqued adequately

Double check that the shift cable/fixing bolt/plate washer are all properly oriented and are not impeding derailleur range of motion.

Verify cable moves smoothly through all housing/bends including bottom bracket guide (do this by hand after loosening fixing bolt).

I prefer to set my derailleur limit stops without a chain on.

Try a different wheel

Verify proper installation of cassette with all spacers.

Use a Park DAG tool to verify hanger alignment

Stick with it and good luck.

Originally Posted by azrider

Hmmmm.........if it were me, and I had done all of that I'd be checking the alignment of the hanger as others have mentioned

Originally Posted by eddief

are the der cable heads seated properly in the shifter?

and i know this sounds dumb but someone i ride with (i swear not me) rode his bike a real long way with the chain not threaded through the rear derailleur correctly. he missed that little thingy right above the bottom pulley.

Originally Posted by weisan

That's not a "worst case scenario" at all, sometimes that's exactly what it takes to regain your sanity!

I went through this scenario a few weeks ago, finally threw in the towel, took a set of shifters and deraileur AND chain AND cassette combo that I know is working perfectly on another bike (that I don't ride that often), transferred them over and voila! everything works as they should. I refused to spend another second trying to figure out why, life's too short, instead took the bike out immediately and rode like a madman!

Originally Posted by OtayBW

Maybe I'm missing something here, but if the chain is riding up on a bigger cog (lower gear), then you'd want to loosen the barrel adjuster, no?

Originally Posted by 93KgBike

My 7800 is old, but not sloppy.

Try, barrel adj. full-right-back-1/8 before cable attachment. Then, fully downshift and, using your thumb, press the derailleur out until the lower jockey wheel is in line with the second cog and take-up the cable slack and tighten. When you release, the derailleur should be properly setup over the 11t. Barrel adjust the gears for noise at 2, and may 12 or so?

And check the b-screw setting, larger gears may change the position.

GL

Originally Posted by giordana93

not sure about your cable routing but make sure (if you have one) that the guide under the bottom bracket isn't loose. and make sure there are no kinks obviously (you prolly did but worth mentioning). couldn't hurt to make sure the last loop into the derailleur gets a drop of tri-flow or similar. sure sounds like the cable is hanging up somewhere or there's a "loose connection" like that guide pivoting or a ferrule not sitting squarely

Originally Posted by jc031699

Agree with this
If the chain is riding up on the cog that it’s on already, the cable is too tight. If you have the cable adjusters all at “zero” it implies that you can’t decrease cable tension. Is that true? ... being adjusted on the stand is not the same as being adjusted under load and at 90-100 rpm cadence, maybe just needs a click or two looser on the cable adjuster while riding to get just right.

Also, are you sure you are clamping the cable in the right place on the RD cable fixing bolt? Sometimes the little clamp plate rotates around into the wrong position when you have it all apart. This can have a subtle effect on the shift ratio.

https://www.sheldonbrown.com/dura-ace.html

Originally Posted by bitpuddle

As mentioned, I’d try a Shimano chain, if possible.

If you took off/replaced the cassette, make sure all the spacers are in the right place and that none of the cogs have any play. Remove and reseat if there is any doubt.

OK, an update for the team -the "Argh" continues!

Thank you for all of the suggestions. I've gone through each of these to see if they would address the issue. Unfortunately, it still persists. Here's what I've done so far (*reminder - this is following a complete set of new cables, housing, chain, and cassette):

-Swapped out the cassette for ANOTHER new cassette.
-Swapped out the rear wheel with another (unfortunately, the rear cassette was dirty and contaminated my chain with grit - had to clean it, my chainrings, and jockey wheels as a result).
-Checked all cable housing ends - all good.
-Checked the BB cable guide - all good.
-Turned the chain around the other way - although the KMC chain isn't unidirectional.
-Took a link out of the chain.
-Checked the chain multiple times for sticky links.
-Rechecked and adjusted all limit screws as suggested above.
-Turned barrel adjusters on frame and derailleur all the way in and then backed them out about a 1/3rd the way.
-Checked B Screw and adjusted it across the range to test.
-Checked for kinks in shift cable and that it moves smoothly in the housing.
-Adjusted the barrel adjusters across their range to test.
-Replaced the shifter itself with a known working unit.
-Replaced the rear derailleur with a known working unit.

After all of this, the EXACT same problem persists in the exact same manner. The bike shifts well as it did previously. However, the chain pops and jumps randomly when sitting on a rear cog (the 4th, 5th, 6th) when just pedaling along. And it doesn't happen at a consistent spot on the chain while the pedals are being turned.

So... the only two things that I haven't tried are the following suggestions:

Originally Posted by Black Dog

Try a different chain from a different brand.

Originally Posted by azrider

Hmmmm.........if it were me, and I had done all of that I'd be checking the alignment of the hanger as others have mentioned

I'm going to try a new Shimano chain tomorrow. The KMCs are known to be great chains, but perhaps this particular one has an issue.

I haven't checked the derailleur hanger for alignment, but will order a tool to do so once I test the chain.

Could ferrule size compared to the shift cable have an effect? I used metal ferrules instead of plastic and they're just a tiny bit larger than the housing diameter and fit loosely as a result. Could that do anything?

Thanks again for all of the suggestions so far. Although there's a more-than-capable bike shop less than a 1/2 mile from my house, I'd prefer to figure this out.

Thanks!

Texbike

[Ken Robb]

It MUST be operator error!