[Closed] Sudden strange chain problem(video included)

Chain+cassete+chainring+pulleys were replaced in January .I have a chain gauge, the chain is not 0.75% worn. The 10th work perfectly till now, not a single skip when pedaling as hard as I can. Now it skips even when pedaling slow.

Bent tooth?

At 0:42 you can see the tooth that the chain rides up on.

Thanks for stopping by 🙂

I thought that could be the problem too, but if you look at the first two videos, the chain starts climbing in different places.  Firstly the chain starts to climb starting from the tooth located before the "11T" marking on the lockring. In the second video it starts climbing 2 teeth before that place.

has the wheel been out, is it still seated completely?

Bent mech hanger - could be very slight

Too much tension in the cable - if you wind barrel out a bit does the mech move (unlikely this, but have a look)

Failing all that, start again from scratch - new cable, make sure the mech goes from 1-10 by hand by setting H/L screws, then recable and adjust appropriately.

Wheel is seated ok, cog hasn't yet been out of the cassette.

The hanger couldn't get bent when simply changing 9th to 10th cog in a decent manner...

Inner and outer cables were also replaced in January. However, the cable doesn't matter since it's no tension in it, when in the 10th cog. Mech goes from 1-10, and as said previously, all 1-9 cogs on each chaining work ok. I'll take tomorrow a closer look.

Is the cable actually slack and is the mech sitting on the H limit screw?  Can you pull it any further over with your fingers?

Yep, cable is loose and mech sits on H limit: any change in the H screw moves the hanger.

That is how a new(er) chain on a worn cassette behaves.  Is there any way you might have used the 10th cog off your old cassette on the new one?

Definitely not. I replaced everything in January at the same time.

I'd say then chain has stretched on some links. Only way to rule that or any issue with the chain out, is to get another or pop an old one on for a start.

Have you tried a parktools style reindex and reset of limit screws? Where you go out the limit then slowly fettle it back in? Also has B-screw fell out, or loose?

I would say the issue is that the tooth about to engage at 15s is damaged, and its likely causing the chain to sit oddly on the other teeth.

I tried adjusting the limit and B screws with no result...Also, the chain starts to "climb" in different places on the cog.

I'll take everything apart today, clean the area, and inspect everything.

It looks to me that several of the teeth are hitting the rollers rather than engaging between them, several links are then sat on top of the teeth resting on the rollers then the chain drops back into place as it drops down ; I've no idea why it's doing this though.

Any chance that the cassette might be loose on the freehub so there's movement?

If it's climbing up in different places then it's not likely to be the cassette. Have you tried using the chain

guage on the places where the chain starts climbing off ? It may not be stretched beyond replacement

n some places but buggered in others ....

Assuming it's not catching on 9th gear then I have to say greyspoke's theory is winning for me. Is there any chance that you got old and new sprocket muddled up?

<span style="font-size: 0.8rem;">It does look like there's some wear or damage on the teeth at the points where it's riding up, particularly the one above the 11T letters. </span>

You sure its a 10sp chain not an 11sp? Seems to sit on top of the wider teeth on the cassette...

It does look like the chain has stretched/worn on one or two links greater than the rest.  I would work my way round the chain with your chain checker and see if there are any sections that are longer than the rest.  Depends upon the accuracy of your gauge obviously but it may show up some areas that are worse than others.  Another way is to spin the chain around slowly about 4-5 times and mark each link that does it, if it's the same place in the chain consistently then you know the culprit.  Easiest way to check is to chuck a new chain on and see if it solves the problem, if not you have a spare chain.

Check for stiff links in the chain

+1 for stiff link.

any change in the H screw moves the hanger.

???

When i speak of hanger I mean the (usually sacrificial) bit that joins the derailleur to the frame. It screws or bolts on and is designed to break if if all goes tits up rather than the frame itself.

You said there was no chance to damage the hanger ("The hanger couldn’t get bent when simply changing 9th to 10th cog in a decent manner…") but I'm wondering if your definition of hanger and mine is different?  And mech hangers are deliberately built fragile so could have bent without there being a noticeable reason.

Also - is it possible the mech hanger isn't done up tight?

That said, a misaligned mech hanger would probably affct all gears, not just 9/10 but as Sherlock says, rule everything out and what's left, however improbable, is your answer.

My first impression is a stiff link.

Clutching at straws here..........

Other than that, is the chain directional?

How's the freehold? Have the bearings collapsed?

Whats your chain line like? Is it too stretched in 10th?

@PJay
The cassette didn't seem to be loose.

@therevokid
I'll check this today. However, everything worked perfectly until yesterday. Then, in a matter of a second, when shifting from 9th to 10th cog, the problem appeared. I imagine it can't be chain wear since it worked perfectly before, and now skips all the time even when pedaling slowly.

@pdw
No chance of mixing cogs up. Cassette(+chain+others) were replaced at the same time in January, and worked perfectly together until now. Also, the old cassette was black coated.
Regarding the wear you are mentioning, no idea what could have instantly cause that when just shifting gears. I'll everything apart today and look closer.

@mrjmt
Shimano CS-M771 and KMC X10, worked perfectly together since January.

@theotherjonv
Sorry, I had mixed up hanger with derailleur cage.
But regardless, a normal shifting shouldn't damage any of these. And yes, all other gears work flawless.

@damascus
I checked the chain quickly but didn't notice any stiff links. The slipping happens continuously,  maybe 3-4 times per 360° pedal movement. No chance that many links suddenly got stiff at the same time. Chain doesn't appear to be stretched...
How’s the freehold? Have the bearings collapsed? 
Sorry, not sure what you are referring to.

This afternoon I'll provide pics and additional videos, after cleaning the drivetrain completely.
Thanks everyone for the help !

Bit of a shot in the dark, but I don't suppose that the chain is starting to try to upshift to the 9th cog again which might suggest a lack of outward movement? Cable tension and/or H Limit screw adjustment would be something to play with, but it sounds as if you've already tried this; did you loosen off the cable when you played with the H screw?

There have been some threads recently about certain SRAM mechs. suddenly refusing to drop the chain onto the smallest cog due to failing mech. return springs; I can see that you've got a Shimano mech. but it might be worth a look. What happens if you undo the cable, loosen off the H screw and apply a little outward pressure with you're finger; does it still skip?

Do it once to establish the link and tooth. Paint the link and tooth with a Sharpie. Keep rotating to see if it is the tooth repeating the issue of the chain link.

I also think it will be a stiff link.

Being able to pull the cable under load is different to unloaded...

Have you tried changing the cable inners and outers?

A while ago I switched EVERY component except the cable outers... (between bikes) and was about to give up when someone suggested changing the cable... worth a go and it also makes shifting feel new again 😀

Weird one - chain 'stretched' would seem to be the opposite of what the video is showing - at certain points the chain links are [i]too short[/i] to engage in the next tooth. Maybe the whole chain is too long... and therefore there's not enough tension to pull it across the teeth correctly. I've certainly had that problem in the past myself.

@theotherjonv
Sorry, I had mixed up hanger with derailleur cage.
But regardless, a normal shifting shouldn’t damage any of these. And yes, all other gears work flawless.

You'd be surprised what can bend a mech hanger, they are designed to be fragile.

I'd look at the mech hanger. It takes 10 minutes to swap over to a new one, worth doing to check, if you have a spare.

I had issues once with shifting and the hanger was the culprit. I don't know what caused it to bend and it was only very slight.

Also, shot bearings can play with shifting. Worth checking for any movement there. Again quite an easy swap if you have spares kicking around.

How’s the freehold? Have the bearings collapsed?

Sorry, auto correct. Meant to say freehub.

10th cog and this chain: they don't "match" anymore. Why?

big chain miracle...(?!?)

My guess: only new cassette and new chain will solve it.

Are you filming this upside down. Does it do it as bad the right way round?

Can you put up a picture of it in 1st and 10th so we can see you chain length?

Failing finding a solution, dial in the limit screw and never use 10th gear again.

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 !

haha

great research!!!

(these straws... - evil stuff...)

I cant believe none of you mentioned it might be a bit of straw,standards slipping round here.

That's more like a branch! That's why I periodically use a flat screwdriver to clean the spaces between the first 3 sprockets.

covered with hardened black stuff

Chuck that Finish Line lube away!

I cant believe none of you mentioned it might be a bit of straw,standards slipping round here.

Well he did say he constantly cleans and greases his drivetrain - how was anyone to know he was speaking in the Trumpian sense!

@DezB

I thought the Finish Line dry lube is top quality. Do you have other recommendations ?

@theotherjonv

I really clean it often, but rarely remove the cassette. Looks like I'll do it more frequently from now on.

there's just too many nooks and crannies in a cassette for you to be able to clean it without taking it apart.

Road ones, might be different as there's far less debris likely to go in there, but even then still worth it every so often to clean all the road grime off properly.

I thought the Finish Line dry lube is top quality. Do you have other recommendations ?

Good guess eh?! Finish Line is shit. Unless you like hard black stuff forming on all your bits.

Fenwicks dry, Weldtite Pure dry, Muc Off dry, Rock n Roll, or ProGold. Take yer pick 🙂

I like this'un cos it's cheap and Halfords do it

"http://www.chainreactioncycles.com/weldtite-pure-dry-lube/rp-prod148917"