Chain flapping noise after new drivetrain installed - Any ideas?

[egroover]

Hello all,

I've replaced my chain, cassette and derailleur today and am now experiencing a chain flapping noise when riding. I checked the chain length using a calculator (114 links). My chain is a KMC x9 114 links, the new cassette is a SunRace 11-40t 9 speed and the new derailleur is a Shimano Alivio long cage RD-M3100. I have previously run the same chain and cassette on the bike without issue, the derailleur I previously ran was an Shimano Altus long cage 9 speed ( the next model down in the range from Alivio ) with no issues

I have checked High/Low screws, gear selection is spot on, and have checked and tried different B screw adjustments, but no different. I have created a short video below with the bike on the work stand, where I have attempted to replicate the noise when riding by applying the rear brake to simulate load (just spinning without load on bike stand doesn't show the issue)

Any ideas guys ? The new chain is lubed, the alignment looks OK (hanger not bent), I'm fresh out of ideas. The new Alivio derailleur is a slightly different design than the previous Altus one, in that there is a built in bit that drops down from the hanger, like a wolf tooth hanger adapter. I'm thinking the derailleur is the issue as the cassette/chain combo worked fine with the previous derailleur

 

[thelarkbox]

Is your chain too long, try removing a link and check you can access all gears?

 

[matthewslack]

With a very critical eye, check your front chainring. Unless it is also new, it is the exception and they do not last forever. I got only 3 chains worth of life out of my first one, by which time there was extreme chain suck with new chain number 4, and on examination rather hooked teeth.

I have just replaced everything except chainring, and there is slight unhappy noise from it - it'll be swapped as soon as I can get the pedal pulled off to get at it.

 

[saneagle]

The chain looks too long to me. the derailleur is more or less vertical in bottom gear. I would have expected it to be reaching more forward.

Regardless of that, I think you're getting chain suck because the chain is new and has to make quite an angle to reach across to first gear, which makes it tight where it leaves the chainwheel. It should loosen up after a bit of use.

 

[egroover]

Thanks all, some great suggestions and advice ! In the video, I was in 3rd or 4th gear, it's less noticeable in 1st gear if I remember rightly.

Chain suck, of course, knowing the right term for the issue helps a lot (cheers @saneagle ), I can see that now from the video, the chainring is hanging onto the chain a tooth or two as it leaves

I'll try removing a link or two from the chain. I'll also check the chainring for wear, maybe add a bit more lube. Hopefully it'll settle after a few rides

Cheers all, as always, super helpful

 

[saneagle]

Thanks all, some great suggestions and advice ! In the video, I was in 3rd or 4th gear, it's less noticeable in 1st gear if I remember rightly.

Chain suck, of course, knowing the right term for the issue helps a lot (cheers @saneagle ), I can see that now from the video, the chainring is hanging onto the chain a tooth or two as it leaves

I'll try removing a link or two from the chain. I'll also check the chainring for wear, maybe add a bit more lube. Hopefully it'll settle after a few rides

Cheers all, as always, super helpful

Leave it for a week or so to see if it frees up. Loads of people get problems with new chains that go away on their own after a short while.

 

[egroover]

Leave it for a week or so to see if it frees up. Loads of people get problems with new chains that go away on their own after a short while.

Good advice, I'll do that

 

[guerney]

With a very critical eye, check your front chainring. Unless it is also new, it is the exception and they do not last forever. I got only 3 chains worth of life out of my first one, by which time there was extreme chain suck with new chain number 4, and on examination rather hooked teeth.

I have just replaced everything except chainring, and there is slight unhappy noise from it - it'll be swapped as soon as I can get the pedal pulled off to get at it.

Bafang's steel chainrings last quite a long time. I don't know if my 52T needs replacing just yet.

Here's my spare 48T, almost new.





Here's my 52T after 4000 km + something (must check ODO)





EDIT: Hmmm... I've ordered a replacement 52T, just in case. They don't cost much:

44T 52T For BAFANG BBS01 BBS02 Mid Motor Chain Wheel Chainring Teeth Replacement | eBay

Teeth Number: 44T/ 52T (Optional). Chain Wheel Material: Iron SPCC/Aluminum Alloy. Chain Line: 50. Suitability: MM G340.

www.ebay.co.uk

 

[saneagle]

Bafang's steel chainrings last quite a long time. I don't know if my 52T needs replacing just yet.

Here's my spare 48T, almost new.


View attachment 56418


Here's my 52T after 4000 km + something (must check ODO)


View attachment 56417


EDIT: Hmmm... I've ordered a replacement 52T, just in case....

That's like new. I left mine on until it was slipping. It still worked as long as I didn't pedal too hard. It looks like you have quite a way to go yet.

I sold it to the local timberyard:

 

[guerney]

That's like new. I left mine on until it was slipping. It still worked as long as I didn't pedal too hard. It looks like you have quite a way to go yet.

I sold it to the local timberyard:

View attachment 56421

Thank you, very interesting - also, very impressively worn. I worried that keeping photos of my chainwheels would be nerdiness gone too far, but it appears you've got that well covered - I realise I needn't have worried, seems I'm in the wrong place for worrying about bike related geekery in all it's forms.

When the new one arrives, I might upload detailed photos of old and new 52T chainwheel teeth, for those of us who like that sort of thing. I might even attempt to measure a tooth height or two.

 

[saneagle]

Thank you, very interesting - also, very impressively worn. I worried that keeping photos of my chainwheels would be nerdiness gone too far, but it appears you've got that well covered - I realise I needn't have worried, seems I'm in the wrong place for worrying about bike related geekery in all it's forms.

When the new one arrives, I might upload detailed photos of old and new 52T chainwheel teeth, for those of us who like that sort of thing. I might even attempt to measure a tooth height or two.

I kept that photo for reference so that I could show guys like you when to worry about wear. Too often, people see the first sign that their part is no longer new, then panic about replacement.

Chain wear tools were a fantastic invention by bicycle shops. Not only do they profit from selling them, but they also get profit from the never ending demand for new chains and sprockets. Life was much simpler when I was at school and those tools didn't exist. We did many thousands of miles on our bikes and nobody ever had to buy a new chain or sprocket.

 

[guerney]

I kept that photo for reference so that I could show guys like you when to worry about wear. Too often, people see the first sign that their part is no longer new, then panic about replacement.

I'm really glad you uploaded your photo showing normal chainwheel wear. My chainline is ever so slightly off, and every so often my chain leaps off the chainwheel - rare, not worrying, I simply put the chain back on and carry on. It's difficult to tell because of the grime, but it appears these two teeth (at the very least - I'll remove and clean up this chainwheel for a proper inspection when the new chainwheel turns up) are slightly notched at the tops... which led me to suspect the chainline being slightly off has caused the chain to bite into them.

I'll upload highly thrilling detailed photos of my old chainwheel teeth in about 2 weeks, as usual the new 52T is being sent from China despite claiming to be "UK STOCK!" Oh well, at least there's no VAT added at checkout - ebay's price shown was the price paid, unlike AliExpress.

It's a rare issue, and if the new 52T doesn't solve it, I've simply bought a spare, and it's good to have spares.

(crop of photo in post #8)

 

[saneagle]

I'm really glad you uploaded your photo showing normal chainwheel wear. My chainline is ever so slightly off, and every so often my chain leaps off the chainwheel - rare, not worrying, I simply put the chain back on and carry on. It's difficult to tell because of the grime, but it appears these two teeth (at the very least - I'll remove and clean up this chainwheel for a proper inspection when the new chainwheel turns up) are slightly notched at the tops... which led me to suspect the chainline being slightly off has caused the chain to bite into them.

I'll upload highly thrilling detailed photos of my old chainwheel teeth in about 2 weeks, as usual the new 52T is being sent from China despite claiming to be "UK STOCK!" Oh well, at least there's no VAT added at checkout - ebay's price shown was the price paid, unlike AliExpress.

It's a rare issue, and if the new 52T doesn't solve it, I've simply bought a spare, and it's good to have spares.

(crop of photo in post #8)
View attachment 56431

The tops of the teeth don't do anything. That's probably how they've been since new. The wear happens at the bottom unless the chain slips over the teeth, and a slipping chain couldn't make the teeth go like that.

When I was QA manager, I invented the science of quality management. The first law of QA that underpins the science is: "The more you check, the more you find". The corollary to that are: If you don't check for faults, you won't find any. You need to check the right amount, so I developed a technique I called "dynamic quality control", where you adjust the amount of checking in accordance with the history of faults and the risk of faults in the future.

Anyway, back to your bike, you're checking it too much. It'll tell you when something needs sorting. When the chain starts grinding it needs oil. When your chainring needs replacing, it'll slip under very heavy loads, which gives you plenty of warning to replace it before it slips all the time.

 

[guerney]

The new 52T arrived unexpectedly quickly, but 1T is slightly damaged. My previous 52T looked perfect on arrival. Whaddya reckon? Will this tooth cause issues? Should I be enraged and demand a refund?

 

[saneagle]

The new 52T arrived unexpectedly quickly, but 1T is slightly damaged. My previous 52T looked perfect on arrival. Whaddya reckon? Will this tooth cause issues? Should I be enraged and demand a refund?


View attachment 56443

No it won't.

 

[egroover]

The new 52T arrived unexpectedly quickly, but 1T is slightly damaged. My previous 52T looked perfect on arrival. Whaddya reckon? Will this tooth cause issues? Should I be enraged and demand a refund?


View attachment 56443

I reckon they'll all look like that after a 100 miles

 

[guerney]

I reckon they'll all look like that after a 100 miles

What? I'm going to get 100 miles less from this brand new chainwheel?!?!? I'm foaming at the mouth with rage! Seller's ignoring me, obviously thinks it's a non-issue.

Have you resolved the chain flapping issue yet? I would have removed a link or two.

 

[egroover]

What? I'm going to get 100 miles less from this brand new chainwheel?!?!? I'm foaming at the mouth with rage! Seller's ignoring me, obviously thinks it's a non-issue.

Have you resolved the chain flapping issue yet? I would have removed a link or two.

Hoping to get back on it tomorrow removing a link. I've got a brand new Bafang kit 44t chainwheel still in the box to test if needed. Might even switch back to that as don't need the lower geared 42t so much now I've given up the off road use of the bike in the last year (big off resulting in 3 broken ribs, busted shoulder etc)

 

[I893469365902345609348566]

Was it a badger?

 

[guerney]

Might even switch back to that as don't need the lower geared 42t so much now I've given up the off road use of the bike in the last year (big off resulting in 3 broken ribs, busted shoulder etc)

Very nasty. Why did you do all that? Hope you've fully recovered.