Just putting a rear mech on my Explosif SS for an upcoming big ride – just flicking through the gears and finding that the [new KMC] chain is riding up on the 11T sprocket every couple of links (no other sprockets involved) until the chain is sitting on top of the teeth, then plopping down into the teeth. I bought a new chain because this also happened on my old {slightly worn SRAM] chain and thought it was a wear issue. Both chains are 8spd, as is the Shimano block. Rear mech is an old XTR, and never had problems with it in the past. Front ring is a 32T Surly SS.

I have replaced the 11T with another one laying around.
It doesn't skip on the neighbouring 12T, and all other sprockets are fine.
I have slid the dropouts forward, backward and all points in between in case it was a 'chainstay' length issue.
The teeth aren't broken, the chain is perfect.
The mech cage distance adjuster screw is set to max.

The only thing I can think of is a nackered top jockey wheel which is goosing up the chain being fed to the 11T sprocket…

Any suggestions appreciated.

Have you fitted a new lockring on the cassette by any chance, some have a larger diameter than others and will cause those very symptoms.

I'm sure I've read that someone's quicklinks don't work well with 11t sprockets – maybe it's KMC's

or maybe you've a slightly sticky link that only shows up on the "tightest" bend

dirty cable ? – spring'll be at it's slackest at the outer sprocket

you sure the hanger isn't a bit bent ?

No, the lockring isn't touching the chain.

Interesting point – I'm using an SRAM Powerlink on the KMC chain. I'd have thought the link length was the same regardless of make. Still, I had the same problem with SRAM chain and a different pair of Powerlinks! I've always had 11Ts and SRAM chains and this is the first time I've encountered this. I knew I should've stuck with SS – give me all these wasted hours back!

No sticky links as this happens more than once per revolution.

Cable is fine (new inner and outer, hmm maybe it's the pimpy white outer lol) and I'm adjusting the limit screws as well.

The hanger is a slidey type, about 8mm thick! Nope, all sitting square and straight…

Oh well, thanks anyway. Guess I'll be using the 12T as my bottom. What's a tooth, eh?

Morning bump

I seem to remember having the same problem happening with a older chain with a newer powerlink added. Pretty sure it was a SRAM powerlink but cant remember the chain make…

I just tried to avoid the 11t but in the end I gave in a bought a new chain which fixed it in my case.

How worn was the chain last used on the XTR cassette and replacement 11t?

What was wrong with the KMC quick link that came with the chain, why not use that?

'mech cage adjuster screw is set to max'? – do you mean the B tension screw?

Hip – the old SRAM chain was part worn, maybe 6 months old. The cassette isn't XTR, but mid range somethingorother. The KMC is a silver/black one and didn't come with a quick link, hence using the Powerlink. But TBH this happens when the link isn't going through the cassette, so it's not the problem.

hazeii – that's the badboy. Can never remember the name for it.

are both the chain and cassette new? Most common cause ( as I am sure you know) is a mix of worn and unworn parts

Is the cable totally slack and allowing the mech to move right accross? try releasing the cable totally.

Bent mech or mech hanger

TJ, the 11T isn't brand new, but doesn't show much sign of wear. It's as if the pitch between the chain links is slightly longer. And the other sprockets, which are the same age as the 11T, work absolutely perfectly even under pressure.

The top jockey is sitting directly underneath the last sprocket and feeding the chain straight onto the 11T.

I'd say a bent hanger too, but really these sliding drops really are too wide/thick to bend.

Hmm just got a 105 11t (on a new cassette) and new KMC chain and its fine! My old cassette looked hardly worn but after forgetting to change the chain for a year wore over .75 and rear cassette was knackwered and started jumping with a new KMC chain on.

Otherwise sounds like a chainline problem rear end i.e. hanger and mech – worn rings usually jump on torque not rise up IME.

lee – a sprocket does not have to have visible wear to be too worn to mesh and the smaller the sprocket the more acute the issue also smaller sprockets wear faster than large ones.

I ain't saying for sure its the issue ( as you had the same issue with a worn chain) but the next thing I would try would be a new cassette.

Yeah, I need to swing by a shop anyway, will see if they have any unused 11T sprockets lying around 😉

Definitely 2nd the worn cassette theory.

The smaller rings tend to wear quicker as fewer teeth mean they're under greater force per tooth. I'd be cautious about just replacing the 11tooth sprocket too (if you can find one) as the others will most likely be worn to a lesser degree, shortening the life of your new chain.

the others will most likely be worn to a lesser degree, shortening the life of your new chain

fbk, believe me, after this weekend the geared stuff is going into that nice storage box in my cupboard and I'm getting my single 15T King cog put back on 😆

I second tj, while at the shop get them to check the hanger is straight (they will have a tool and fitting it and adjusting it won't take long) regardless of how thick it is it still might not be straight, I currently have a similar problem on my 223 which is probably 10mm thick in that area.

Also, is your chain too long? Just an idea since your B tension is maxed and only having a problem in your slackest gear.

Good luck

Sorry lee, misread XTR mech, assumed cassette… 😳

I also have an explosif and agree there's no way the sliding dropout would be bent. I'm sure the frame would bend first…

Would agree with several other posters above, looking like a mix of old and new…

Just out of interest did you measure the old chain, how much longer was it? I had one of the cheaper KMC chains on my SS and it wore very quickly indeed. A 410 IIRC.

Interested what your shop says, please let us know.

Hmm I have a KMC SS chain and even after 8 months of riding it still stretches after a good ride! I never measure chains. I should finally buy a chain wear indicator thingy but never got round to it. If I solve it I'll post back. It'll probably be one of those obvious solutions where we're looking at it too scientifically…!

No need for a wear indicator, all you need is a tape measure. Quote from Sheldon Brown.

Measuring Chain Wear

The standard way to measure chain wear is with a ruler or steel tape measure. This can be done without removing the chain from the bicycle. The normal technique is to measure a one-foot length, placing an inch mark of the ruler exactly in the middle of one rivet, then looking at the corresponding rivet 12 complete links away. On a new, unworn chain, this rivet will also line up exactly with an inch mark. With a worn chain, the rivet will be past the inch mark.

This gives a direct measurement of the wear to the chain, and an indirect measurement of the wear to the sprockets:

* If the rivet is less than 1/16" past the mark, all is well.

* If the rivet is 1/16" past the mark, you should replace the chain, but the sprockets are probably undamaged.

* If the rivet is 1/8" past the mark, you have left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you replace a chain at the 1/8" point, without replacing the sprockets, it may run OK and not skip, but the worn sprockets will cause the new chain to wear much faster than it should, until it catches up with the wear state of the sprockets.

* If the rivet is past the 1/8" mark, a new chain will almost certainly skip on the worn sprockets, especially the smaller ones.

hip

Hip – which is quicker measuring with a tool or a tape measure – I have a chain wear indicator tool and takes me 2 secs to put it on – I agreee no real need but makes it quicker for me anyway!

Yep – as foxyrider said – the measuring tool doesn't cost much and enables you to do the job in a few seconds with the chain on the bike. How often does the average person take their chain off the bike, never mind measure it's length.

It's hardly an essential tool but it I never bothered checking chain wear until I got one.

foxy – I may just have to invest in one and give it a try.

fbk – no need to take the chain off, just measure over 12 complete links, 12 inches. There is enough room to measure when the bikes upside down getting its chain lubed. 🙂

I bet you all a fiver that it's the end stop screw. If it's snagging once per revolution then it's just trying to climb gears.
Bet is null and void if the hanger is bent.

Hip – didn't want it to sound like you needed one but tis quicker and easier IMHO 🙂

NP foxy. Looking at them they also take the cylinder/pin interface wear into account which could be a good thing, but I would have thought plates, pins and cylinders wear at around the same rate so I'm still on the fence over them.

When I've got a spare tenner I might invest in the Park CC-3 but in the meantime I'd rather spend that tenner on a chain… 🙂

bikewhipserer – bottom stop screw is irrelevant; it's not happening once per evolution, just under pressure. As above there's no way the hanger could bend 😀

Cheers for the wear info as well.

I ended up riding the whole way (404 miles) using 7 of the 8 sprockets (28T-12T) and a 32T chainring, and to be honest only missed the bottom 11T once or twice coming off the big hills. Pah to 27 speed… all you need is 7 😆

Limit screw.

9 times out of 10 it will be a worn cog on the cassette. If it does it under tension it will be a worn 11t sprocket. It would be handy if you had a new one spare to try.

Yes, I'm going to pick up one next time I'm passing.

Unless someone has a spare one they don't need…?