Why does my new chain look stretched?

Just fitted a new m6100 cassette and chain. By the time it gets round to the derailleur it seems to be missing the teeth?

TommyC said:

Just fitted a new m6100 cassette and chain. By the time it gets round to the derailleur it seems to be missing the teeth?

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I'd say that I could be that your cassette is worn and not meshing with the chain correctly. Do you have a chain checker to measure the chain?

It’s all brand new. The whole bike even. Nothing worn.

directional chain on backwards??

So just been talking it through with the seller on eBay. Adamant it’s all genuine Shimano and I’ve no reason not to believe him. All looks legit. Tried a spare m6100 chain I keep for my emtb (picture is from analogue bike) and the same thing so likely the cassette.

Seller is going to exchange for a 7100 cassette as no 6100 left so we’ll see.

Mikerb said:

directional chain on backwards??

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There’s only an arrow on the quick link but I’ve always put chains on with writing facing outwards. Or is that just some bs I dreamt up?

Check the chain with an idiot proof chain gauge, my preference is the pedro's one. Make sure your B-tension is set properly and that your chain is cut to the proper length. There is a lot of counterfit shimano stuff on the market right now... I would not buy through ebay in the future as the counterfit risk is too high.

I fail to see how a b-tension screw or number of links in a chain going to affect this? Here’s another pic. It’s out over the span of 10 or so links. Same with spare chain I had that I bought from my lbs.

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Long time since I had a shimano drivetrain, but is it narrow wide? Maybe you just need to move the chain forward one cog?

The cassette teeth look like they're not even cut correctly to me.

ebsocalmtb said:

There is a lot of counterfit shimano stuff on the market right now... I would not buy through ebay in the future as the counterfit risk is too high.

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This ^^^

TommyC said:

There’s only an arrow on the quick link but I’ve always put chains on with writing facing outwards. Or is that just some bs I dreamt up?

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yes....chain link markings facing ouwards and the right way up on the top loop of the chain. The OPs chain looks to be upside down to me.

Mikerb said:

The OPs chain looks to be upside down to me.

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It was at that point. Was trying it every which way I could to see if it made a difference. It does not.

Measure the distance between chain pins to measure stretch, at 12" centre to centre on a new chain it should be exactly 12".

Amber Valley Guy said:

Measure the distance between chain pins to measure stretch, at 12" centre to centre on a new chain it should be exactly 12".

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I agree, but not 12" +/- half of 1/16", not even just a bit past the black line on the tape. It should be spot on.


To measure accurately a 12" length of chain, you really need two people. One to hold one of the key indicators (like an inch marker) exactly over then centre of a pin. The second to keep the chain taut and to look at where the exact centre of their pin is in relation to the inch marker. You don't have to be limited by the intervals on the steel rule (usually 1/16"). You can estimate for yourself easily one quarter of that gap, ie 1/64".

Even if both people are out by 1/64" (which I doubt), the worst it could be is an error of 1/32". That is near as makes no difference one quarter of one percent. Accuracy would be tripled if you measured over 36".

I measure over 100 links (50"). Accuracy is one sixteenth of 1%. (Or one twelfth of the 0.75% before reject time).

I think the seller has shipped the M6100FC cassette, which is optimised for extreme cold climates and will only work correctly with the chain once it's shrunk slightly.

(FC= Fecking Cold).

So I pulled the other bike today with the same cassette and chain and the same thing. This still has the original cassette on it so 100% legit. Tried 3 identical chains, 2 new including one bought from 99 bikes, all the same.

We sure it’s not meant to be like this?

Done 500 miles on this cassette and never had any issue. Works perfectly

Mikerb said:

The OPs chain looks to be upside down to me.

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Noticed this on all 3 chains too

I dont know if the picture of the chain on the Shimano website is typical of every chain manufactured, in terms of how each link is marked and in what order. You can see below the links do indeed vary in terms of the writing sometimes being the right way up and sometimes upside down.

Is you're chainring shagged? Did you measure the chains pin to pin over 12"?

TommyC said:

Just fitted a new m6100 cassette and chain. By the time it gets round to the derailleur it seems to be missing the teeth?

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Are you sure just not looking at the chain on the shifting ramps? (HG cassettes are designed to throw the chain off at certain points)

Measured both new chains and they’re spot on. Again nothing is worn, it’s a brand new build

TommyC said:

Joten vedin tänään toisen pyörän samalla kasetilla ja ketjulla ja samalla asialla. Tässä on edelleen alkuperäinen kasetti, joten se on 100% laillinen. Kokeiltu 3 identtistä ketjua, 2 uutta, joista yksi ostettu 99 pyörästä, kaikki samat.

Olemmeko varmoja, ettei sen ole tarkoitus olla näin?

Tällä kasetilla ajettu 500 mailia, eikä koskaan ollut mitään ongelmia. Toimii täydellisesti

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Ketju venynyt paljon, kasetin hammastus lähes uusi.Eli ketju ei pääse pohjaan alaosan kuvassa,se on kulunut rulla osineen väljäksi.Eli hammaspyörän pohja kouru ei saa näkyä ketjun alta.

Streddaz said:

I'd say that I could be that your cassette is worn and not meshing with the chain correctly. Do you have a chain checker to measure the chain?

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Question, how does the chain fit onthe rest of the cassette sprockets??? Is it still to big or does it lay on the teeth correctly?

CaptKirk said:

Question, how does the chain fit onthe rest of the cassette sprockets??? Is it still to big or does it lay on the teeth correctly?

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Good point.

CaptKirk said:

Question, how does the chain fit onthe rest of the cassette sprockets??? Is it still to big or does it lay on the teeth correctly?

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It was still off. I’ve got the replacement slx cassette and it still seems a little loose with a slack chain around it. But when it’s all fitted to the bike and set up it works a treat