Chain riding on sprocket teeth (Campagnolo 12 speed)

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taylorpetie
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Joined: Tue May 19, 2015 4:55 pm
Location: California

by taylorpetie

Hoping to have some guidance. This happens intermittently (probably 1 out of every 10 times or so...) when I shift to the 25T and/or 32T sprocket, the chain would sometimes ride on the sprocket teeth and then reseat itself (see pic below). When climbing, this would cause a jolt of course. Aside from this, every other sprocket shifts fine.

Image

Image

Current setup: C60 frame with Campagnolo SR 12, with 11-32 cassette. Rear derailleur hanger is straight (vertical, horizontal), chain is not stretched (i.e. fairly new), 11-32 cassette is fairly new as well, cassette is tightened to correct torque settings, upper pulley wheel is close as possible to cassette (5-6mm), high and low limit screws adjusted, cable tension adjusted (more on slacker side, if the cable tension is more tight, then shifting isn't that great).... I've played around with cable tension, B screw, etc... to no avail

Any guidance is much appreciated.

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pdlpsher1
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by pdlpsher1

Since this is only happening on the 32 cog, I suspect the culprit is the top pulley wheel is too close to the cog. Leave a space about 10mm and see if the problem goes away.

I’m on Shimano Di2. If I adjust the top pulley close to the largest cog, about 20% of the shifts to the largest cog will have a clunking noise. It’s hard to see visually what causes the clunk but I suspect it’s from the chain not settling down on the tooth properly. After I increase the distance the noise goes away with no detriment to shifting accuracy on any of the other gears.


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by Weenie


alcatraz
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by alcatraz

When I index I like to see how see how consistent the chain position is.

I focus on the gap between the chain and the next larger cog. I compare this gap in different gears to see it doesn't vary too much. If it does there might be some other issue. If I can slide 1-2 sheets of printer paper between the chain and cog I'm usually happy.

It's common that the optimum indexing is 1-3 barrel adjuster clicks different when done on the biggest cogs compared to the smallest. You then end up somewhere inbetween with a slight misalignment on the extreme ends of the cassette.

If you think the upper pulley has too much sideways play you can try to lower it by swapping or bringing it closer to the cogs. If it has too little play it could need to wear in or increase pulley/cassette distance.

Alexandrumarian
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Location: Romania

by Alexandrumarian

I had this too once on my 11s. It was something off about the limit screws, cable tension or maybe both. I only fixed it by releasing the cable and starting the tuning from scratch.

alcatraz
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by alcatraz

Oh yeah, check that the cable is clamped on the right side of the clamping bolt.

wilwil
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Joined: Thu Sep 23, 2010 5:47 pm

by wilwil

Have you looked at the Campag instructions for the rear mech set up? They are quite specific about how to use the screw at the top of the mech to acheive the correct jockey to cog distance. Forget about your sheets of paper.

taylorpetie
Posts: 67
Joined: Tue May 19, 2015 4:55 pm
Location: California

by taylorpetie

wilwil wrote:
Wed May 01, 2019 5:05 pm
Have you looked at the Campag instructions for the rear mech set up? They are quite specific about how to use the screw at the top of the mech to acheive the correct jockey to cog distance. Forget about your sheets of paper.
I don't have any 'sheets of paper' to forget but I assume you are referring to these two Campag instructions, and yes I've read them....
https://www.campagnolo.com/media/files/ ... 9_2018.pdf
https://www.campagnolo.com/media/files/ ... _11_18.pdf

taylorpetie
Posts: 67
Joined: Tue May 19, 2015 4:55 pm
Location: California

by taylorpetie

Thanks to others with the constructive input/feedback -- much appreciated. I'll keep adjusting/refining... As mentioned, it intermittently happens only on cog 25T and 32T. While I spend most of my riding between 12T and 22T ... and only rely on the larger cogs on steep hills of 18% or higher so I don't get a heart-attack :)

But, it would be good to know that this intermittent issue doesn't happen (even if it only occurs 1 out of every 10 or so times).

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Calnago
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by Calnago

It shouldn't happen. Start over. I'm going to assume (usually a highly irresponsible thing to do), that your hanger is straight, cables are run nice and smooth, no hangups, and they are seated in the levers properly. Ok, now that we know that all those things are good... we know that right?... let's proceed as I think this is a very simple adjustment issue.

First, let's talk. Does the chain seem be over shifting a bit, as if a bit more would throw it into the spokes, or not quite shifting enough, as in it's thinking "I think I can I think I can" as it tries to climb to the larger sprocket. I ask because, despite you saying that it's shifting pretty well overall, I would question that and say it's shifting like crap, and it is, based on what you say and show. I think you're starting point is slightly off, and as it moves up the cassette, that error becomes more noticeable as it tries to climb the cassette and jump bigger gaps. I ask the question about which way it is off to ascertain if the low limit screw (the screw that limits the derailleur from going into the spokes, needs any adjusting from the get go (i.e., to loosen it off if that's what's preventing it from getting to the largest cog). But I suspect that it's the opposite and the limit screw is already loosened off enough and the chain is actually riding a little too far towards the spokes), so you can leave that screw untouched for the moment. Further reinforcing that theory is that it's having problems on the 25 cog as well, where absolutely no limit screw adjustment is at play.
The other thing I notice is that the spring on the adjusting barrel is almost, if not completely, bottomed out, making any adjustment difficult if the cable was tightened to the anchor bolt when it was quite taught to be begin with. That's important to note, because it could limit our options during adjustment to get the exact starting point.

Ok, so what is the "starting point". It's just that, with no cable attached (yes, undo it completely), make sure the upper pulley is as aligned to the smallest sprocket as possible. It's harder to do with the chain on, and I usually do this step before installing the chain. But the chain is on, so it just may take a bit more fiddling, no biggie. Also, loosen the adjuster barrel on the derailleur a couple of turns so that you actaully sill have some useable adjustment in both directions.

Ok now, loosen off the upper limit screw a bit (the one that limits the derailleur from going into the chain/seat stays). You don't want that limiting the starting point at this time and this may in fact be the entire cause of your issue, it may be too far in. But loosening it off won't affect anything if the cable is too tight and can't be adjusted for the reason I just gave concerning the adjusting barrel position. That's why we're starting from scratch and detaching the cable, as well as giving the adjusting barrel some room to breathe in both directions.
Ok, now that you've loosened off the upper limit screw, and loosened the ajdusting barrel a couple of turns, just play with the lower limit screw a bit while pedalling (in a stand), but without the rear derailleur cable attached. Loosen it until you can hear bad things starting to happen (it's too far outboard), then tigthten it until you can hear the same things start to happen on the inner side, where you can hear the chain wanting to start climbing to the second cog. Obviously that's too far in. You need to set the limit screw in the middle, or even ever so slightly outboard of the middle (and then take up the tiny slack with the adjustment barrel) of perfect alignment between the upper pulley and the smallest cog.
Now, reattach the rear derailleur cable, taking all the play out, but not so tight that you're actually actuating the derailleur with no lever movement (oh yeah, of course make sure your lever is postioned so that it would be on the smallest cog during this process).
Ok, so with cable reattached, some adjustment available in both directions via the adjustment barrel, and the starting point as close as you could get it, play with the shifting just between the smallest and second smallest cog. You should be able to go back and forth easily, and use the adjusting barrel to make sure you can. Listen for any noises that might indicate less than perfect alignment and adjust accordingly. If I nail this adjustment between these two cogs, the rest are usually perfect. Usually :) .
But lets' check things out. Ok. In the stand, just shift up one by one, nice and easy, making sure each shift is perfect. If you sense it wants to overshift anywhere, then loosen the adjusting barrel a smidge, and vice versa if it's having a bit of a tough time at any stage climbing to the next cog. Back and forth, back and forth, until it's perfect. A this point, if done right, I suspect you're going to able to shift right on up to the largest cog no problem.
Now, assuming you're smiling and all proud of yourself because it seems to be working, it's time to dial in the lower limit screw. The key is to have it so that the shift from the second largest sprocket to the largest is easy and not in any way encumbered by the limit screw, but that the limit screw is just "on the limit" of it going any further. I'm going to make another assumption here and assume you know how to do that. Check how close your upper pulley is to the spoke crossings at this point, ensuring that no contact is going to happen. Once you have the limit screw set, actually try to shift into the spokes (slowly of course), just to make sure your limit screw is doing what i'ts supposed to be doing, namely, not allowing that to happen.

Ok, almost there.
You said you had the upper pulley within about 5mm of the largest cog earlier. That's good, it's where you want it. As close to the cogs as possible without the chain jamming in between the cogs and pulleys. Having it further away than necessary only does one of two things...

1) If the shifting was crisp to begin with, moving the pulley away will only make it less crisp. It'll still shift ok, but not as crisp as if it were as close as possible to the cogs. This is always the goal and why so much effort has been made by both Shimano and Campagnolo of late to improve this.

2) If the shifting was not quite perfect due to indexing being slightly off to begin with, moving the pulley away may mask some of this sloppiness by introducing some new sloppiness simply as a result of moving the pulley further away from the cogs, lulling you into a false sense that your shifting is "ok", even "perfect" maybe. I like to explain it like this... Imagine the upper pulley as close to the cogs as possible... and there is one little tiny shift gremlin sitting in his easy chair reading a book at his leisure, right up close there. When he gets the signal to shift, all he does is reach his hand over and lightly touch the pulley and bam, because of it's close proximity to the cogs, pickup is quick and easy and it shifts. Easy peasy. But now imagine the pulley way far away from the cogs. The chain has to be lifted up then dragged across the gap until it catches the pickup. It takes at least 3 or 4 of those little shift gremlins (yes I've counted) to do the same job as just the one sitting in his easy chair up nice and close. Plus, those 3 or 4 are constantly running back and forth dragging that heavy chain... it's just no fun. Treat your shift gremlins nice, and they'll return the favor.

That's it. Of course I've made quite a few assumptions right at the beginning of my post, and that's always a caveat, but if things are good there, and you follow what I've just written, you should be up and running in no time, and that one little shifting gremlin can relax and the others can go home until they're really needed, hopefully never.

Cheers! :beerchug:
Last edited by Calnago on Wed May 01, 2019 8:08 pm, edited 1 time in total.
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Alexandrumarian
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Location: Romania

by Alexandrumarian

Cal, thanks for the effort, I'm sure a lot of people will appreciate it (as it was with the front tuning writeup)! Good points in particular about the small cog positioning. If that is bad one can spend a lot of effort with the cable tension and it will still be off. By eye I can never be sure it is perfect, so I try to see and count how many screw turns are in between each position extremes. Meaning, I turn the screw until the chain is clicking about to jump outside the cassette. Turn back and count until it start clicking about to climb the second cog, then set the screw in the middle. Also good point about starting with the barrel at about 80% not fully closed. I do the same on the front adjuster, sometimes we pull the cable in too hard.

wilwil
Posts: 366
Joined: Thu Sep 23, 2010 5:47 pm

by wilwil

taylorpetie wrote:
Wed May 01, 2019 6:46 pm
wilwil wrote:
Wed May 01, 2019 5:05 pm
Have you looked at the Campag instructions for the rear mech set up? They are quite specific about how to use the screw at the top of the mech to acheive the correct jockey to cog distance. Forget about your sheets of paper.
I don't have any 'sheets of paper' to forget but I assume you are referring to these two Campag instructions, and yes I've read them....
https://www.campagnolo.com/media/files/ ... 9_2018.pdf
https://www.campagnolo.com/media/files/ ... _11_18.pdf
Sorry that was alcatraz

wilwil
Posts: 366
Joined: Thu Sep 23, 2010 5:47 pm

by wilwil

taylorpetie wrote:
Wed May 01, 2019 6:46 pm
wilwil wrote:
Wed May 01, 2019 5:05 pm
Have you looked at the Campag instructions for the rear mech set up? They are quite specific about how to use the screw at the top of the mech to acheive the correct jockey to cog distance. Forget about your sheets of paper.
I don't have any 'sheets of paper' to forget but I assume you are referring to these two Campag instructions, and yes I've read them....
https://www.campagnolo.com/media/files/ ... 9_2018.pdf
https://www.campagnolo.com/media/files/ ... _11_18.pdf
Yes page 9 of the second PDF where they talk about the chain angle from the cog to the jockey wheel

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Calnago
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by Calnago

Alexandrumarian wrote:...By eye I can never be sure it is perfect, so I try to see and count how many screw turns are in between each position extremes. Meaning, I turn the screw until the chain is clicking about to jump outside the cassette. Turn back and count until it start clicking about to climb the second cog, then set the screw in the middle. Also good point about starting with the barrel at about 80% not fully closed. I do the same on the front adjuster, sometimes we pull the cable in too hard.
That’s exactly what I do (count the turns between extremes that turn it back half of those turns to get it very close). But figured I was getting too detailed as it was. However, when the chain is already on that is an excellent way of determining where the “middle” alignment starting point is. I kind of got him started by saying to fiddle with the adjustment back and forth and listen for the extreme points. Hopefully he comes back a happy camper. If not, one of “assumptions” was clearly wrong. Image
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
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alcatraz
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Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

I've never actually used paper :lol:

Just trying to quantify the chain/cog gap somehow.

Going by shift speed alone doesn't really position the chain in a non-cog-rubbing position or give you a clue whats going on when the chain rides the cogs.

Seeing the gap vary between 11th/10th cog and 2nd/1st is an indicator that you need a certain amount of chain deflection to eat up the difference. Either by increasing pulley distance/sideplay or changing pulley tooth profile.

Ideally it'd be great with no chain deflection and no gap difference, and super low pulley/cog distance for lightning fast shifts, but we don't live in a perfect world :D.

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pdlpsher1
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Location: CO

by pdlpsher1

Cal,

I know your preference towards having a small gap between the top pulley to the largest cog. Next time when you have a Shadow-based Di2 bike in your hands, adjust the B screw for a small gap and try shifting from the second largest cog to the largest cog, and see if you hear a clunk on a small percentage of shifts. I tried to reduce the pulley wheel gap on my bike but I get the 'clunk' on perhaps 20% of the shifts from the second largest to the largest cog. Increasing the gap solves the problem. I don't think the noise is an indication of a bad or missed shift. But the noise just doesn't sound good when all other cogs shift without any noise. Perahaps this is a Shadow Di2 specific problem. I now have Di2 on my tandem as well and it does the same thing. I'm just curious if you can duplicate the problem on another Di2 bike you have access to.

taylorpetie,

When you say your RD hanger is straight did you actually check it with a hanger alignment tool? Sometimes people say their hanger is straight but they have never checked it with a tool. A hanger can be misaligned on a brand new bike that's never been crashed or mishandled. Even the slightest hanger misalignment will cause shifting problems. Also another common problem is a loose hanger. Take your wheels off and make sure those two philips screws are tight. And wiggle the hanger with your hand to detect any movement. There should not be any movement on the hanger with the wheels off.

by Weenie


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