[Cdl888]

Has anyone had any experience of KMC chains failing prematurely? I have a 9 speed Sora equipped bike permanently on my Wahoo Kickr. The groupset is in good condition with no parts especially worn. The drivetrain is kept spotless and dry lubed regularly.

My old KMC X9 chain basically exploded about a month ago with countless broken links. I put it down to wear and tear, purchasing another KMC X9 however that chain did a similar exploding trick tonight and upon inspection there are at least 13 cracked links. It’s done less than 100km indoors.

 I’ve used KMC chains for years with no problems but this really puts me off. Thankfully I was on the turbo so no harm done, but outside in traffic the result could have been very different!

I’m sure the retailer will warranty replace it but before I accept a replacement KMC I thought I’d canvass opinion here on possible causes?

Topic

[HLaB]

I’ve never had a 9sp KMC
I’ve never had a 9sp KMC chain but I did have an 11sp one fail (warped link) on its 2nd or 3rd dry ride. I’ve had quite a few KMC chains before that which lasted a high mileage until they’ve slipped or not sat correctly on the chainrings (not actually snapped), so I gave them another go and I’ve had no problem since.

[Simon E]

I have been using KMC 9 speed

I have been using KMC 9 speed chains for a long time and never had any issues.

[huntswheelers]

Blimey…that is shocking…

Blimey…that is shocking… we have used KMC for years with no problem but there are some KMC fakes about and 9 speed versions were in short supply during Covid so I managed to stock Sram 9 speed chains at that time. I still have stock of those as the majority of my customers are 10 speed plus end users. I hope you get resolved soon, you could always try Taya as they always work well

[wtjs]

My Vitus Sora 9-speed ‘gravel

My Vitus Sora 9-speed ‘gravel’ will soon have done 3 years and 15-18,000 miles- on a total of 4 chains: the original and 3 cheap KMC chains. I have a system where I remove them when they reach the first wear point using a Rohloff chain wear tool, and then bring them back in rotation until the second wear point. They have all been faultless, and I have never in 55 years of cycling broken a chain. I will then be moving to 46/30 and 11-34 from the present 48/32 and 11-32- this bike has done a lot of heavy trailer towing, and many muddy tracks such as the entire Pennine Bridleway

[stonojnr]

Yes I’ve had a KMC chain,
Yes I’ve had a KMC chain, 9speed also, snap multiple links on me and hadn’t done anywhere near the mileage I’d expect for KMC chain. Though again bought from reputable online source, though the last one I bought from them came in a plastic bag, not the normal plastic case. my feeling is theres either a bad batch of them out there, or there are a large number of fakes in circulation.

I only replaced another broken KMC chain last week, probably more likely wear on this one, but it let go as I pulled away with an HGV sat an inch off my back wheel, who was also blocking a box junction for good measure, so that was exciting.

[Cdl888]

Chain was bought from a

Chain was bought from a reputable online retailer, one of the biggies so would be disappointed if it was fake.

I don’t think it’s a load issue. I’m no heavyweight at 78kg with a max power at sprint of about 1000w. Also all the rides on it bar one have been fairly tame recovery rides due to the heat and getting in some decent outdoor rides. 

Mech alignment and such like checked with no obvious issue. 

Old chain was definitely due replacement but still surprised to see so many cracked links.

To clarify, exploded is a bit colourful… one link totally snapped and upon inspection there are at least 13 links cracked. 

My gut is that I’ve just been unlucky with the last chain, but want to rule out any other cause. I have since found some forums from a few years back where KMC chains were failing but they claim it was a single bad batch with a particular marking that this one does not have. 

[IanMSpencer]

KMC X9 is a decent chain and
KMC X9 is a decent chain and I fitted a gazillion of them in my time. Off hand I can’t think of a reason why a chain would fail like that without there being some reasonably obvious drive chain problem, such as a distorted rear mech twisting the chain, but I’m sure you’d hear and see such an extreme fault. I would not be surprised with a single failure on a new chain, it does happen across all brands, though fairly rare, but multiple links I’ve never seen.

My instinct is that it is a fake chain, there are certainly fake KMC quicklinks around on Amazon. With all the messing about over the last couple of years, the other alternative is that KMC have outsourced to someone not making parts to spec.

My only doubt is that both your chains failed unusually. To have multiple links fail simultaneously doesn’t make sense to me (not saying it didn’t happen, just can’t understand how a chain would fall into multiple pieces when a link failed), which does make me wonder if there is some issue on the bike. What sort of mileage had the old chain done? An X9 should be good for about 3000km assuming it is being ridden in a normal style. A caveat on trainers is that it is possible to put unusual loads through bikes, e.g. resistance cranked right up and grinding on the pedals (I’ve seen a hub destroyed by a trainer). If you are carrying a bit of weight, fit rugby player for example, out of the pedals and resistance high, might it be that you’ve put too much load through the chain?

[Author]

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