chain broken, could it be the result of cleaning method?

[confusedcyclist]

Last night my chain broke on the way home, resulting in a lengthy walk home, thankfully punctuated with a few downhill coasts to break the mundane progress

I didn't take a picture of my chain after the event as it was dark, and I was in a hurry to get home, it went in the nearest bin rather than soiling my bag, but the break looked like this.

Only last week I cleaned the chain in an ultrasonic bath of degreaser, then it was thoroughly lubricated again with wet oil and used a chain checker on it only a week ago and established it wasn't yet .5% worn. Given it was so clean and well maintained, I'm just wondering what are the mechanics that leads to this failure if a chain isn't overly worn, and how can it be avoided in the future? Is it just metal fatigue? I've no idea exactly how many miles the chain has ridden, but given the lack of noticeable wear, I'm baffled.

 

[Darius_Jedburgh]

It's a KMC chain. There have been reports of KMC chains breaking for no apparent reason. I've no idea how accurate those reports are but some of the sources are usually reliable.

 

[fossyant]

It happens. Could have been caused by a bad shift at some point.

Always carry a chain splitter and quick link. I damaged a link on a bad shift with worn chain rings on my MTB in summer (I'd ridden the bike loads this year) - fixed very fast with the splitter on my multi tool, and spare quick link fitted. Binned the chain after, and I would advise you do the same.

I'm not keen on 'SL' chains with the cut outs.

 

[Eric Olthwaite]

It can be caused by the wrong choice of lubricant...

 

[confusedcyclist]

It's a KMC chain. There have been reports of KMC chains breaking for no apparent reason. I've no idea how accurate those reports are but some of the sources are usually reliable.

Since it's now in the bin in the middle of Bradford City Centre, I can't prove it, but I'm certain it was a Shimano chain, the image is just to demonstrate the type of failure. My own experience with various KMC chains has been positive, I've used them consistently for tens of thousands of miles of riding, never experienced this with KMC. It did happen once to me in 2015, but that fell down a storm drain so didn't get to inspect the failure!

It can be caused by the wrong choice of lubricant...

I think it's fair to say wet oil is standard fare for UK riding.

...Always carry a chain splitter and quick link.
I'm not keen on 'SL' chains with the cut outs.

Thanks, I had one on my cheapo multi tool, but it completely failed to push out the broken link pin and even bent under the stain, next time I'll carry my shop quality park tool breaker.

 

[fossyant]

Crank Bros multi tool for the win.

 

[Ajax Bay]

Given your chain was a Shimano chain, and that you'd very recently taken it off to clean it, and given the way it failed (as illustrated in the image (ack not of your binned chain), I postulate that, in all likelihood, it failed at the link you rejoined - assume with a pushed in pin rather than a quicklink. If you joined it with a quicklink, then I suggest the most likely failure link was the one that the chain had been joined at when newly fitted.
It must have been frustrating to carry a chain tool, albeit one of those minute ones on a multi-tool, and then not be able to rely on it. I carry one of the lightweight Topeak tools which has seen me OK (fixing only other people's failed chains, I hasten to add).

 

[Profpointy]

Surely taking it on and off to clean is the most likely cause of weakening it, assuming it's
not just bad luck

 

[confusedcyclist]

Hmm, no actually I add quick links to all my chains, regardless of brand for ease of servicing.

 

[Ajax Bay]

It can be caused by the wrong choice of lubricant...

 

[Juan Kog]

To repeat earlier very sound advice , chain splitter plus (the correct) link . Also I carry a compact head torch ,petzl ultra compact is my choice. I also prefer to carry a separate chain tool . I do have a multi tool with a chain tool , I did try the multi tool chain splitter in the warm workshop , with bike on work stand . It was OK.
But would I want to use it on a freezing winters night in very poor light , No. When I’m out on fixed with 1/8 chain I also carry short length of chain 2 links as well as a joining link.

 

[Cycleops]

As above, won't bring your shoe leather back but your walk could have been avoided if you'd carried one of these:

Plus some wet wipes of course. 👍

 

[snorri]

. I do have a multi tool with a chain tool , ............. But would I want to use it on a freezing winters night in very poor light , No.

Your post shows a refreshing honesty often missing from roadside repair tips offered on a cycling forum.

 

[I like Skol]

But would I want to use it on a freezing winters night in very poor light ,

No use carrying tools that are not upto the job when it hits the fan!

Can't stress this enough, wether it is for a simple puncture repair or more involved roadside procedures, but you must practice at home and be familiar with the operation when using the tools that you will have available at the roadside. Discover any failings during practice rather than when stranded.

Back to the OP, if you suffered the failure type as shown in your picture I would be reasonably confident that this is due to the chain previously being split/rejoined there. Modern narrow chains have peened pins that are very effective at resisting seperation. IME the side plate is more likely to crack than an untouched factory installed pin to fail. You say it was a shimano chain. Was this originally fitted to the bike using the shimano single use joining pin and then split elsewhere by yourself to fit the missing link type connector?

FWIW, fixing the failure shown above even on a cold dark night should pose little problem and the longest amount of time would be taken getting the tool out and checking for any obvious causes. The repair itself should just take a minute or two, with a reasonable tool and a spare split link to hand.

 

[confusedcyclist]

You say it was a shimano chain. Was this originally fitted to the bike using the shimano single use joining pin and then split elsewhere by yourself to fit the missing link type connector?

Yes!

The repair itself should just take a minute or two, with a reasonable tool and a spare split link to hand.

Indeed, I've used similar tools many a time, just not the multi tool I had on me last night. Bad luck, poor tools, and lesson learned!