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Sudden strange chain problem(video included)

Old 07-16-18, 11:13 AM
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Sudden strange chain problem(video included)

Today as I was shifting between the 9th and 10th(last) cog, applying just slight pressure on the pedals, something very strange happened. The chain suddenly started slipping skipping(whatever is the correct term) on the 10 cog. It now happens all the time, even when the pedals are just slightly pressed. All 9 other cogs work perfectly. I constantly clean and grease my drivetrain, and the chain+cogs are not worn.

Here is a video which explains better:



I thought the H limit screw could've somehow moved so I tried to adjust it with no result. The chain doesn't "climb" on the 9th cog.

I also experimented with the B screw with no result. I also took the wheel off and cleaned the 10th cog and pulleys.


Any idea of what could have happened ? I can clearly see in the video what's happening but can't think of what could be the cause.

Thanks a lot
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Old 07-16-18, 11:19 AM
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Put a new chain and cassette on the bike
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Old 07-16-18, 11:27 AM
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Originally Posted by trailangel
Put a new chain and cassette on the bike
Chain and cassette have been replaced in January. Chain is not yet .75% worn. 10th cog worked perfectly before, not a single skip. Did you even read my post ?
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Old 07-16-18, 11:32 AM
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Yes I did read, and you didn't say you replaced chain and cassette in Jan. You said they are not worn. Cassette looks worn to me.
Have you checked your deraileur hanger alignment?
Don't put bike upside down.
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Old 07-16-18, 11:43 AM
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Are you sure that the high limit screw is adjusted properly. On shimano the pulley should a little outboard of center. The chain and cassette wear together and do not skip as they wear. A new chain on a worn out cassette will skip.
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Old 07-16-18, 12:18 PM
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Originally Posted by trailangel
Yes I did read, and you didn't say you replaced chain and cassette in Jan. You said they are not worn. Cassette looks worn to me.
Have you checked your deraileur hanger alignment?
Don't put bike upside down.
I also replaced chainrings and pulleys in January, if it matters. I have a chain gauge, and it shows the chain is not yet 0.75% worn. I don't think the cassette can wear faster than the chain. Regardless, until today the chain never slipped on the 10th cog, even when pedaling as hard as I can. Now it slips all the time, even when pedaling slowly.

Originally Posted by davidad
Are you sure that the high limit screw is adjusted properly. On shimano the pulley should a little outboard of center. The chain and cassette wear together and do not skip as they wear. A new chain on a worn out cassette will skip.
Yes, pretty sure. Actually I also tried to adjust it so that the pulley stays quite far on the outside, to make sure the chain doesn't climb on the 9th cog.
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Old 07-16-18, 12:23 PM
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Another possibility is to check your cable for fraying or anything that would cause it to stick.
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Old 07-16-18, 12:36 PM
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Do you ride in the cog a lot? 11t cogs wear twice as fast as a 22t cog.

It sure looks like a wear issue with the chain and cog no longer being the same pitch. A worn cog does have a different pitch than it started with, and there is no easy way of measuring cog wear directly.
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Old 07-16-18, 12:46 PM
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The angle of attack looks ok, but that chain just resists slipping into those teeth. Looks to me like the chain is awfully dry and that might be a contributor. (Really nice and clear video to help show what’s going on.)
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Old 07-16-18, 12:57 PM
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Originally Posted by Crankycrank
Another possibility is to check your cable for fraying or anything that would cause it to stick.
Cable is ok. Inner and outer cable were also replaced in January. However, the cable doesn't really matter, since in the 10th gear it has no tension in it.

Originally Posted by Kontact
Do you ride in the cog a lot? 11t cogs wear twice as fast as a 22t cog.

It sure looks like a wear issue with the chain and cog no longer being the same pitch. A worn cog does have a different pitch than it started with, and there is no easy way of measuring cog wear directly.
The 11t is not quite the most used cog. Also read my previous reply to trailangel. I've had this before, when a cog wears out, the chain firstly starts skipping when pushing hard on the pedals, and then gradually also starts to skip when pedaling with less force. In the current situation it started suddenly skipping all the time.
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Old 07-16-18, 12:59 PM
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Originally Posted by Richard8655
The angle of attack looks ok, but that chain just resists slipping into those teeth. Looks to me like the chain is awfully dry and that might be a contributor. (Really nice and clear video to help show what’s going on.)
Chain was lubed yesterday with Finish Line dry lube. However, before filming I cleaned it up with a rag.
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Old 07-16-18, 01:07 PM
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I can't help, but kudos for a very good video!
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Old 07-16-18, 01:16 PM
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Originally Posted by cpper
The 11t is not quite the most used cog. Also read my previous reply to trailangel. I've had this before, when a cog wears out, the chain firstly starts skipping when pushing hard on the pedals, and then gradually also starts to skip when pedaling with less force. In the current situation it started suddenly skipping all the time.
I had read your previous posts, which all have the tone of this one. You sound like you know better and have more experience than anyone who could help you, so you clearly don't need any help from us. Hopefully no one else makes the mistake of trying to.
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Old 07-16-18, 01:43 PM
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Originally Posted by Kontact
I had read your previous posts, which all have the tone of this one. You sound like you know better and have more experience than anyone who could help you, so you clearly don't need any help from us. Hopefully no one else makes the mistake of trying to.
With I've had this before I was speaking about what was following, the cassette wear namely. Sorry if you got it wrong, english is not my native language.
You're saying the problem is wear. The 10th cog worked perfectly until today, even when pedaling as hard as possible. In a matter of a second it stared slipping even when pedaling slowly. I knew wear causes problems gradually. Is this not true ?
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Old 07-16-18, 02:38 PM
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I've followed the Park Tool videos over the last couple of weeks to get my gears shifting smoothly on all my bikes. It might be worth going back to basics and checking everything mentioned in this video:

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Old 07-16-18, 02:42 PM
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Originally Posted by cpper
With I've had this before I was speaking about what was following, the cassette wear namely. Sorry if you got it wrong, english is not my native language.
You're saying the problem is wear. The 10th cog worked perfectly until today, even when pedaling as hard as possible. In a matter of a second it stared slipping even when pedaling slowly. I knew wear causes problems gradually. Is this not true ?
Anything that wears goes from working to not working at some particular point in time - especially if you only have 11t. You appear to have reached that point. It certainly doesn't appear to be related to the lateral movement of the derailleur and you said you've checked your chain (I'm assuming with a chain checker and not just a ruler). There isn't anything left.

Put a new cassette on. If it goes away, then it was wear. If it doesn't go away, post about it again.

You might also look at a gear chart and see if there is a better gear combination that doesn't have you riding in your highest rear cog as much. Most people only use that cog downhill or when sprinting.
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Old 07-16-18, 03:08 PM
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Originally Posted by cpper
Today as I was shifting between the 9th and 10th(last) cog, applying just slight pressure on the pedals, something very strange happened. The chain suddenly started slipping skipping(whatever is the correct term) on the 10 cog. It now happens all the time, even when the pedals are just slightly pressed. All 9 other cogs work perfectly. I constantly clean and grease my drivetrain, and the chain+cogs are not worn.

Here is a video which explains better:

https://www.youtube.com/watch?v=VxvhziBC5j4


I thought the H limit screw could've somehow moved so I tried to adjust it with no result. The chain doesn't "climb" on the 9th cog.

I also experimented with the B screw with no result. I also took the wheel off and cleaned the 10th cog and pulleys.


Any idea of what could have happened ? I can clearly see in the video what's happening but can't think of what could be the cause.

Thanks a lot
It looks to me like there is a tight link one or two links after the quick link. The "jump" you feel is just the chain remeshing with the cogs. Try pedaling backwards and watch for the derailer to jump in much the same way as the tight link goes through the jockey pulleys.

I don't think there is anything wrong with your derailer adjustment.
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Old 07-16-18, 03:21 PM
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Sudden symptom; look for a sudden cause. Bent hanger, bent der, hub bearing failure, loose locknut, an obstruction inside the dropout, etc, who knows. Pull the wheel and touch, feel, listen, look, disassemble, find something obvious.
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Old 07-17-18, 12:44 AM
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Originally Posted by cyccommute
It looks to me like there is a tight link one or two links after the quick link. The "jump" you feel is just the chain remeshing with the cogs. Try pedaling backwards and watch for the derailer to jump in much the same way as the tight link goes through the jockey pulleys.

I don't think there is anything wrong with your derailer adjustment.
I checked the links, there are no stiff ones... Also, when pedaling with my feet(not hands, as in the video) the slips occurs continuously, maybe 3-4 times per 360° pedal movement. When pedaling backwards no issue is to be seen.

Originally Posted by AnkleWork
Sudden symptom; look for a sudden cause. Bent hanger, bent der, hub bearing failure, loose locknut, an obstruction inside the dropout, etc, who knows. Pull the wheel and touch, feel, listen, look, disassemble, find something obvious.
Today I'll do a complete clean of the area, and also take the cassette and 10th cog out for inspection.
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Old 07-17-18, 12:56 AM
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How is the derailleur cage spring doing? Last time i had this problem it was due to low chain tension while on smallest cog.
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Old 07-17-18, 01:04 AM
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Originally Posted by Kovkov
How is the derailleur cage spring doing? Last time i had this problem it was due to low chain tension while on smallest cog.
Spring appeard to be ok, I'll look closer today.
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Old 07-18-18, 09:43 AM
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Since you are trying or have tried numerous solutions, you could check and see if the cassette is tight to the hub. Use a Park FR 5.2 and make sure it is tight. I know you say there are no tight links but I thought the same thing as the poster above when I saw your excellent video. Do you have an older chain just to check it out?

I also disagree that the cassette or 11 tooth cog in particular is worn. You would have to be riding in that cog everyday for hours since you purchase it to be worn. It may wear twice as fast but I don't believe that most people use an 11 tooth cog twice as much as the others. Good luck.
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Old 07-18-18, 09:55 AM
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As I took everything apart yesterday, I found the issue. It was a straw carefully rotated around the groove on the 10th cog, covered with hardened black stuff, making it very hard to notice. I didn't even knew there should be a groove on the cog.
In my first post I said I cleaned the area, but without removing the cogs from the cassette, the stuff there wasn't visible. I cleaned the are between the cogs with a cassette brush but it seems it didn't remove the grime.

Here is the groove which was filled with that straw and black stuff:






And here is the culprit:


I cleaned the area and entire drivetrain, and now everything works super smooth. Thanks to everyone for helping out !
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