Chain Keeps Breaking

[silva]

The link plate towards the crank broke in the middle of its pen hole, I'd say that's the first one that broke, causing the other plate to be torn outwards to then break too, on the position slightly away from pen center due to leverage between rivet strength and outwards force.
If that is a pattern in the breaks, maybe a chainring tooth that got bent out of line, causing excessive fatigue? Or, the connecting link? The pen of the right side, where the break based on aboves thought started, looks like a larger circle than the other pins.

 

[IanSmithCSE]

Good morning,

....I've never seen a single chain break like that, let alone multiple ones at low mileage. It's not normal......

The picture on the post #6 is a stock picture rather than the op's actual chain, so it is of no use, unless of course the op was the one who uploaded the image to the photo sites.

https://www.shutterstock.com/image-photo/broken-bicycle-chain-repair-on-cycling-1845988660
https://www.dreamstime.com/broken-bicycle-chain-repair-cycling-image201519722

Bye

Ian

 

[silva]

..which would explain why the mentioned shimano model showed recessed pin ends instead of rivetted.

 

[ColinJ]

..which would explain why the mentioned shimano model showed recessed pin ends instead of rivetted.

Ah, I thought that those didn't look right!

 

[Bubas]

In the 60 years I've been riding bikes that have chains, I've had plenty that have 'stretched' but I've never broken one.

I've never been heavier than 90 kg though and am currently about 76kg - maybe that's a factor?

Profesional mechanics say that its not. But I dont know if i can agree. It was my first thought.

Bad batch of chains ?

For 6 years?

 

[Bubas]

The link plate towards the crank broke in the middle of its pen hole, I'd say that's the first one that broke, causing the other plate to be torn outwards to then break too, on the position slightly away from pen center due to leverage between rivet strength and outwards force.
If that is a pattern in the breaks, maybe a chainring tooth that got bent out of line, causing excessive fatigue? Or, the connecting link? The pen of the right side, where the break based on aboves thought started, looks like a larger circle than the other pins.

that observation seems useful. I will check on that. Thanks. The post can be locked.

 

[cougie uk]

For 6 years?

You might have stocked up on chains ?

 

[wafter]

This seems very odd as it should take an enormous amount of force to cause those side plates to fail in tension. A dodgy batch of chains could be one answer, or as has already been suggested some drivetrain defect that's loading it up in a way it wasn't designed to accommodate and causing it to fail through fatigue. Some pictures of one the failed chains might help.

For the record I'm a less powerful rider (typical Strava-derived ride averages are maybe 120-130W) and so far have a waxed 11sp KMC chain on my gravel bike that's knocking on the door of 4k mostly dry miles with no signs of imminent failure and practically zero wear..

 

[Dogtrousers]

I'm no expert on this, and have never broken a chain so I have no experience, but I have read on here that user error could be to blame by changing gear harshly and subjecting the chain to repeated lateral loads.

I'm not having a pop at the OP, and I'm an admitted ignoramus, but could this be the case here?

 

[Deleted member 26715]

For the record I'm a less powerful rider (typical Strava-derived ride averages are maybe 120-130W) and so far have a waxed 11sp KMC chain on my gravel bike that's knocking on the door of 4k mostly dry miles with no signs of imminent failure and practically zero wear..

Neither of the chains I've snapped bore 'with no signs of imminent failure and practically zero wear.' until they snapped otherwise I would have changed them?

 

[ColinJ]

I'm no expert on this, and have never broken a chain so I have no experience, but I have read on here that user error could be to blame by changing gear harshly and subjecting the chain to repeated lateral loads.

I have witnessed "user error" killing a chain...

I once took a younger bodybuilder colleague out for an evening ride over the local hills. He was strong enough to break his chain (mashing a 52/13 gear round on a climb! ), but trying to keep up with me half-killed him. (And I am not fast!)

I tried explaining to the body-building gear-masher that it would be better to spin a lower gear because if he carried on like that he would destroy the bike or his knees. He said that it felt weird to him to spin because he was used to 'pumping iron'. And 5 seconds later, his chain exploded under the strain!

 

[Dogtrousers]

Come to think of it, I did once break a chain. A 5 speed. It was in the early 1980s and I'd closed the chain using a nail punch and a hammer.

Teenage me ... a hammer ... mechanical job. I wonder why it broke?

It was a wonderful day. I went to a nearby farmhouse and the farmer offered me a lift to the nearest town. I ended up riding through the Pembrokeshire countryside sitting on a trailer behind a tractor, drinking an enormous mug of tea. At the nearby town I went to a garage and borrowed .... a hammer and punch.

When I got home I bought a chain tool.

 

[fossyant]

I've snapped one or two chains in all my years riding, but they have usually cracked on the link, then you get a tell tale tinkle noise, so I've stopped to check before it's gone, or it's been found during chain oiling. Check, ah broken. Remove link, carry on, bin chain when home. Cross chaining doesn't do chains good, neither does lots of poor shifting.

Always bin a chain after a break, you don't know what damage it's done to other links.

 

[Jody]

I'm no expert on this, and have never broken a chain so I have no experience, but I have read on here that user error could be to blame by changing gear harshly and subjecting the chain to repeated lateral loads.

I'm not having a pop at the OP, and I'm an admitted ignoramus, but could this be the case here?

That's my thought. No blame but crashing up the cassette by multiple cogs whilst under load would be my guess.

Doesn't take much with thin chains used for 11/12 speed

 

[iluvmybike]

Most of the 'unexpected' chain breaks I have seen were down to poor gear changing whilst stomping on the pedals going up hill!