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.

cpach

I wouldn't worry about the rest of the bike overmuch. It really looks like a problem with the actual metalurgy of the chain.

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.

Buzzkill53120

Not an metallurgist, but I did some QA work for a chain company, this could have been a problem with heat treat.

Iride01 

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.

martinori

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.

martinori

That's good to know. It's a relief. My bike should be just fine. I will inform KMC for sure.

martinori

That's helpful. Good to know my cassette is fine! Thanks!

dedhed

I wonder what Papa Ado has to say about this.

martinori

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!

Venturiano

Keep us updated if KMC responds!

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.

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

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...

Camilo

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.

jccaclimber

Just echoing the above, irrelevant lip service from KMC.

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.

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.

martinori

Got it. Just send an email to Papa Ado. Thanks

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....

79pmooney

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.)

ThermionicScott 

Interesting that they call out d-limonene, since a bunch of "citrus" degreasers use that, too.

Crankycrank

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.

79pmooney

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.

koala logs

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.