bike chain failure

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Jul 7, 2014
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Location
Winnipeg MB CA
My younger son rides a single-speed winter bike with studded tires. He phoned yesterday and said the chain had broken. He walked the bike over, and I was surprised to see the nature of the failure. Any chains I've broken have failed with a pin pulling out. This was different though - the actual link had broken, and there was another one that was cracked. He's a tall and strong young man, and I guess is applying a lot of force to the drivetrain. Or perhaps this was a bad batch from SRAM. I suspect the former.

I rode up to my LBS to buy a replacement SRAM single-speed chain, but they were out of stock. They sold me a KMC Chinese-made chain instead. The price was really good. We'll see how it holds up.

Here are some photos of the old chain:

IMG_8476.JPG


IMG_8480.JPG
 
Wow. You're right the usual failure is a link pulling away from the pin. SSing puts lots of force on the chain and sprockets even more so if you have any hills. How old was the chain and did you gauge it for wear?
 
Well, the side plates are rusted, which isn't helping. This being an oil forum, probably worth pointing out that lack of lubrication may have been a factor!

I have seen chains break there before, and they've always had rust on them.

KMC makes quality chains. I've been to their main factory in CN and it's a well-run operation. The make most of Shimano's chains.
 
Originally Posted by AZjeff
Wow. You're right the usual failure is a link pulling away from the pin. SSing puts lots of force on the chain and sprockets even more so if you have any hills. How old was the chain and did you gauge it for wear?
I installed the old chain partway through last winter, so it's less than a year old. Per my Park Tool gauge, the chain is stretched < 0.75%.


Originally Posted by JOD
Well, the side plates are rusted, which isn't helping. This being an oil forum, probably worth pointing out that lack of lubrication may have been a factor!

I have seen chains break there before, and they've always had rust on them.

KMC makes quality chains. I've been to their main factory in CN and it's a well-run operation. The make most of Shimano's chains.
Glad to hear that the KMC chains are good! We'll see how the new one does. Agreed on the rust. Last winter was very hard on the bikes - there were a lot of freeze/thaw cycles late in the season, and the city put down a lot of salt. I would go through a puddle and kick up pure brine. It's hard to keep ahead of the rust.
 
I used Wipperman chains in the past and they used to include an info sheet that noted the breaking strength at 3500 Newton's. I would imagine other good chains are similar. Also note that yours is a single speed chain, the one I mention is a 9 speed, which is somewhat narrower. It's possible a single speed chain being wider is stronger.
I had no issues with Wipperman chains, but I'm also using KMC chains now as I can get them readily. So far so good.
 
Originally Posted by Wheel
I used Wipperman chains in the past and they used to include an info sheet that noted the breaking strength at 3500 Newton's. I would imagine other good chains are similar. Also note that yours is a single speed chain, the one I mention is a 9 speed, which is somewhat narrower. It's possible a single speed chain being wider is stronger.
I had no issues with Wipperman chains, but I'm also using KMC chains now as I can get them readily. So far so good.
3500 N = 357 kg (force) = 785 lbs (force)
Wow, impressive! And agreed, the beefier SS chain would likely be that much stronger. Maybe 1000 lbs?
 
What is the chain-line like on that bike?
A single-speed chain isn't designed to flex sideways as much as a chain for geared bikes and the cracked plate and failed plate look like they cracked where the plate would be subjected to repeated flex if the chain-line was off (chainring and sprocket weren't in-line with each other).
 
Originally Posted by Number_35
3500 N = 357 kg (force) = 785 lbs (force)
Wow, impressive! And agreed, the beefier SS chain would likely be that much stronger. Maybe 1000 lbs?
More for single-speed chains. I suspect the breakage must've been caused by something other than straight pull from pedaling, unless the chainring was very small. Some kind of side force or kinking could do that.
 
Originally Posted by Surestick
What is the chain-line like on that bike?
A single-speed chain isn't designed to flex sideways as much as a chain for geared bikes and the cracked plate and failed plate look like they cracked where the plate would be subjected to repeated flex if the chain-line was off (chainring and sprocket weren't in-line with each other).
Originally Posted by CR94
I suspect the breakage must've been caused by something other than straight pull from pedaling, unless the chainring was very small. Some kind of side force or kinking could do that.

Excellent thoughts on the chain-line! I'll check the alignment next time the bike is here. I guess if it's out of line, I can correct it with spacers.
 
A little off topic but is Dumonde still considered a good bicycle chain lube? Haven't ridden since 2011, but I still have blue and yellow bottles of it, and I loved the blue stuff (I think the yellow was thin, the blue was thicker).
 
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