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Mountain bike chain has multiple links broken

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Mountain bike chain has multiple links broken

Old 05-02-22, 06:15 PM
  #26  
martinori
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Originally Posted by Darth Lefty
Thatís definitely a weird one. My suspicion if something like this turned up at work would be a problem with the batch of steel. Itís hardly your fault. Throw it away and buy a new one and forget about it. Unless you think the effort you were going to put in to get a $20 replacement chain is worth $20.
Yeah, going to get a new chain anyway. I'm also going to ask my local bike shop where I bought the bike for advice as well.

I'm just worried if something else could go wrong that caused this. This is actually very dangerous if happening while riding, guess I'm lucky it happened when I tighten the pedals. I worry if something is wrong with the bike, this could happen again.

Something like bike setting, shifting, cassettes or chainring. Could some other parts of the bike potentially cause something like this?

I read in some other online posts that mentioned bent cassette teeth. I never crash my bike on the cassettes side, but still would like to know if anyone has any experience in this area.
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Old 05-03-22, 12:42 AM
  #27  
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Originally Posted by martinori
Yeah, going to get a new chain anyway. I'm also going to ask my local bike shop where I bought the bike for advice as well.

I'm just worried if something else could go wrong that caused this. This is actually very dangerous if happening while riding, guess I'm lucky it happened when I tighten the pedals. I worry if something is wrong with the bike, this could happen again.

Something like bike setting, shifting, cassettes or chainring. Could some other parts of the bike potentially cause something like this?

I read in some other online posts that mentioned bent cassette teeth. I never crash my bike on the cassettes side, but still would like to know if anyone has any experience in this area.
I wouldn't worry about the rest of the bike overmuch. It really looks like a problem with the actual metalurgy of the chain.
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Old 05-03-22, 09:18 AM
  #28  
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A bent up cassette tooth might eventually through some bad luck result in a mangled side plate, or one popped off of the rivet. Neither of those are what you have here. Your issue is likely isolated to the chain, and from what you have said so far was likely introduced during manufacturing.

Last edited by jccaclimber; 05-04-22 at 08:35 AM.
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Old 05-03-22, 05:47 PM
  #29  
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Not an metallurgist, but I did some QA work for a chain company, this could have been a problem with heat treat.
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Old 05-04-22, 07:56 AM
  #30  
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You should contact KMC and see what they say about it. Send the pic to them in an email to info@kmcchain.us and ask them about it. They need to see it as it does look to me that it might be the result of a bad batch of chains.

Here is their contact page if you are in the USA.

https://kmcchain-us.3dcartstores.com...tion=contactus

If you are in another Country or region you should probably should find the KMC site for your region and use that contact information.

Unless you pedal at 20-40 rpm putting out massive amounts of power standing on the cranks, I can't see how that happened.
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Old 05-04-22, 12:56 PM
  #31  
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Originally Posted by Iride01
You should contact KMC and see what they say about it. Send the pic to them in an email to and ask them about it. They need to see it as it does look to me that it might be the result of a bad batch of chains.

Here is their contact page if you are in the USA.

If you are in another Country or region you should probably should find the KMC site for your region and use that contact information.

Unless you pedal at 20-40 rpm putting out massive amounts of power standing on the cranks, I can't see how that happened.
Thanks for the info! I'm in Canada, I will try to find KMC's contacts. Or send it to US KMC and see what happens.
And yeah, I'm quite new to mountain biking. Don't ride that hard at all.
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Old 05-04-22, 01:02 PM
  #32  
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Originally Posted by Buzzkill53120
Not an metallurgist, but I did some QA work for a chain company, this could have been a problem with heat treat.
That's good to know. It's a relief. My bike should be just fine. I will inform KMC for sure.
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Old 05-04-22, 01:03 PM
  #33  
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Originally Posted by jccaclimber
A bent up cassette tooth might eventually through some bad luck result in a mangled side plate, or one popped off of the rivet. Neither of those are what you have here. Your issue is likely isolated to the chain, and from what you have said so far was likely introduced during manufacturing.
That's helpful. Good to know my cassette is fine! Thanks!
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Old 05-04-22, 06:33 PM
  #34  
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I wonder what Papa Ado has to say about this.
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Old 05-05-22, 04:42 PM
  #35  
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Update: Went to the bike shop today. They also agree that this is a chain defect. They offer to file a warranty as well. I decided to buy a new Shimano chain and keep the breaking chain. (this is my first real mountain bike and first mtb chain)
So I can prove to people I have 10000W legs.
I will also contact KMC to let them know if there is a potential defective batch of chains.

Thank you for the help everyone!
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Old 05-08-22, 09:25 AM
  #36  
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Keep us updated if KMC responds!
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Old 06-06-22, 05:29 PM
  #37  
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Updates from KMC. They first ask me what I use to fill the park tool cleaner. I told them I used Park Tool CG-2.4 Chain Gang Chain Cleaning System with 8 oz. bottle of Bio ChainBrite
A few days later, they replied this:
After reviewing the Park Tool Bio Chainbrite Cleaner used with Chain Gang Chain Cleaning System, we find that it is a natural plant based degreaser. This causes the chain to lose the injected lubrication.
Below is the screenshot for the Bio Chainbrite Cleaner for your reference.
We do not recommend using degreasers to clean our chains as it strips the injected lubricate out of the chain.
We do recommend using soap (non-degreaser type) and water.
Let us know if you have any other additional questions.
Well, I'm not sure about this. I have replied again. Stating I used muc-off dry lube each time after cleaning. And if that will cause harm...
Anyway, just for reference, I really don't think product from parktool would do harm to the chain. But anyway.
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Old 06-06-22, 06:15 PM
  #38  
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Originally Posted by martinori
Updates from KMC. They first ask me what I use to fill the park tool cleaner. I told them I used Park Tool CG-2.4 Chain Gang Chain Cleaning System with 8 oz. bottle of Bio ChainBrite
A few days later, they replied this:


Well, I'm not sure about this. I have replied again. Stating I used muc-off dry lube each time after cleaning. And if that will cause harm...
Anyway, just for reference, I really don't think product from parktool would do harm to the chain. But anyway.
This sounds like a sort of BS reply. They don't address anything about the obvious failures of your chain and fluff you off by not recommending that you degrease the chain without actually saying that the product you used could damage the chain the way it was in your excellent photo. Shame on them for blaming the victim. At a minimum they should have at least sent you a new chain and gained some good will. And guess what? You have already bought a Shimano chain and if it serves you well, may not buy another KMC chain. At the manufacturer's level, a new chain might have cost them less than $5, pretty cheap good will
Your chain cleaning and lubrication regime have nothing to do with the failure mode of your chain and KMC said nothing to claim that it did
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Old 06-06-22, 07:37 PM
  #39  
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Originally Posted by alcjphil
This sounds like a sort of BS reply. They don't address anything about the obvious failures of your chain and fluff you off by not recommending that you degrease the chain without actually saying that the product you used could damage the chain the way it was in your excellent photo. Shame on them for blaming the victim. At a minimum they should have at least sent you a new chain and gained some good will. And guess what? You have already bought a Shimano chain and if it serves you well, may not buy another KMC chain. At the manufacturer's level, a new chain might have cost them less than $5, pretty cheap good will
Your chain cleaning and lubrication regime have nothing to do with the failure mode of your chain and KMC said nothing to claim that it did
Yeah, I'm also a bit disappointed. I don't think a park tool product could damage a chain...They have decent reputations.
I guess I will keep using KMC chains on commuter / cheap bikes. But will use Shimano for my sports bike...
Comparing the KMC X11 and Shimano XT HG701, it does seem X11 is a lot more fragile from the looks of it...Maybe it's a trust issue...
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Old 06-06-22, 10:30 PM
  #40  
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KMC gave a total BS reply to the OP's inquiry. There is no way that the OP's method of cleaning his chain had anything to do with the multiple plate fractures. KMC did not address the issue at all. I'm hoping they reply with a meaninful analysis of this failure. I hope that Papa Ado sees this and contributes to this.

FWIW, I will personally avoid KMC chains at least until someone replies with a satisfactory response, not nonsense.
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Old 06-07-22, 01:09 AM
  #41  
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Just echoing the above, irrelevant lip service from KMC.
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Old 06-07-22, 05:17 AM
  #42  
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Originally Posted by cxwrench
I've never in my life seen a chain fail like that. My guess is counterfeit chain.
I have been duped into buying a cheap 9-speed KMC chain that turned out to be counterfeit. But I never had problems like the OP did. I even took it up a brutal climb similar to Muro di Sormano on a road with cobblestone quality surface and did not have any problems at all. The worst problem I got is rust when I got caught in rain.
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Old 06-07-22, 08:21 AM
  #43  
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Originally Posted by martinori
Yeah, I'm also a bit disappointed. I don't think a park tool product could damage a chain...They have decent reputations.
I guess I will keep using KMC chains on commuter / cheap bikes. But will use Shimano for my sports bike...
Comparing the KMC X11 and Shimano XT HG701, it does seem X11 is a lot more fragile from the looks of it...Maybe it's a trust issue...
Agree KMC's response was BS. Most people degrease their chains at some point and not a rash of failures. You have enough posts to contact Papa Ado directly (KMC rep in Taiwan and BF member) Bike Forums - Send New Private Message or Bike Forums - Send Message I'm guessing he will give you a better answer.

Last edited by Crankycrank; 06-07-22 at 08:25 AM.
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Old 06-07-22, 11:03 AM
  #44  
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Originally Posted by Crankycrank
Agree KMC's response was BS. Most people degrease their chains at some point and not a rash of failures. You have enough posts to contact Papa Ado directly (KMC rep in Taiwan and BF member) Bike Forums - Send New Private Message or Bike Forums - Send Message I'm guessing he will give you a better answer.
Got it. Just send an email to Papa Ado. Thanks
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Old 06-07-22, 11:07 AM
  #45  
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Originally Posted by koala logs
I have been duped into buying a cheap 9-speed KMC chain that turned out to be counterfeit. But I never had problems like the OP did. I even took it up a brutal climb similar to Muro di Sormano on a road with cobblestone quality surface and did not have any problems at all. The worst problem I got is rust when I got caught in rain.
Yeah, the chain that broke in the picture is a 11-speed KMC X11. It comes in stock with the bike.
I actually also bought a few 7/8 speed KMC chains from amazon or aliexpress. They don't have any issue at all.
This is the first time I use a chain from KMC that is above 10 speed.
Maybe KMC is better with 6-9 speed chain....
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Old 06-07-22, 11:17 AM
  #46  
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Originally Posted by sweeks
I'm interested in how this works. A quick Google search seems to indicate that Simple Green is not particularly corrosive to metals. Even if it *were* corrosive, the links on that chain don't look corroded at all.
Simple Green doesn't corrode the steel. With long immersion it changes the grain structure (as I recall reading; I took a metallurgy class 50 years ago but we covered neither bicycle chains nor Simple Green). So cracks can happen in metal that looks perfect. I've been reading about posters having cracks like these in Simple Greened chains for years. (A quick cleaning and good rinse won't hurt anything but days in the full concentration and watch out.)
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Old 06-07-22, 11:19 AM
  #47  
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Originally Posted by jccaclimber
We can debate the concentration and soak time, but the standard Simple Green can cause hydrogen embrittlement in steels, leading to this sort of failure:
https://www.doi.gov/sites/doi.gov/fi...SA_2000-01.pdf
Interesting that they call out d-limonene, since a bunch of "citrus" degreasers use that, too.
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Old 06-07-22, 01:25 PM
  #48  
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Originally Posted by ThermionicScott
Interesting that they call out d-limonene, since a bunch of "citrus" degreasers use that, too.
I'm wondering if some of the citrus cleaners may actually have the same issue but don't normally get used on aircraft so don't get the urgent attention that SG does. Just guessing though.
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Old 06-07-22, 01:53 PM
  #49  
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Off topic - hydrogen embrittlement is very real. The bike of my avatar was built with a Columbus SL fork that was nickle plated but not heat treated afterwards. At 8000 miles with a 160 pound rider and no crashes, the blades developed cracks around the bottom of the fork crown, 2/3ds circumference on one side, 1/3 on the other. Learned later that nickle plating high strength steel drives hydrogen atoms (molecules?) into the alloy and that a light heat treat was required to drive them out. And those atoms/molecules act like gravel in mortar; not what you want in your house when a small earthquake happens.

The cracks we are seeing here aren't that different from what I had. Now, granted, I didn't spend a lot of time investigating them. Way too close to home for me! (I lived through (barely) a Lambert fork breaking. I'd just ridden that fork down 2000' of descents.
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Old 06-07-22, 07:34 PM
  #50  
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Originally Posted by martinori
Yeah, the chain that broke in the picture is a 11-speed KMC X11. It comes in stock with the bike.
I actually also bought a few 7/8 speed KMC chains from amazon or aliexpress. They don't have any issue at all.
This is the first time I use a chain from KMC that is above 10 speed.
Maybe KMC is better with 6-9 speed chain....
Yours looks like a mfg defect. I suspect the pins are too tight and cracked the plates. 10+ speed chains tends to be more fragile. They use thin plates. I often hear chain breaks from riders who are on 10 speed or more cassettes but almost never from 9 speed and below.

Admittedly, I have never used "proper" degreaser on my chains. I tend to use diesel to degrease my chains. But only once during the entire life of the chain to remove the factory grease. After that, I never degrease the chain again.
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