# whats the chance of a chain snapping?



## BigTex_BMC (Dec 30, 2011)

I started doing different intervals, among them are sprinting intervals. This got me wondering how reliable road bike chains are. I used to ride bmx up until a couple of years ago and anyone who has ridden bmx has gone over the handle bars a couple of times do to the chain snapping. 

I have yet to see this happen to anyone on a road bike, so my thinking is that it doesn't happen very often.


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## tihsepa (Nov 27, 2008)

It happens.

Usually on a well worn chain or something that has been abused. Keep everything in good order and you will be fine.


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## wim (Feb 28, 2005)

While it does happen, it's really rare for a properly installed and maintained quality chain. The number one cause by far for a chain to "snap" is improper installation, and especially so if it was done with a replacement pin rather than a master link. With 10-speed chains, the replacement pin method margin of error is very small, almost zero.

I used to do intervals and still ride a bit of track (500-meter TT with a standing start, you can imagine the forces on a chain) and have never had a chain problem that wasn't due to my installation error.


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## Pirx (Aug 9, 2009)

It's extremely unlikely with a well-maintained chain. A good chain will withstand forces in excess of 2000lbs without complaint.


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## Seagoon (Nov 22, 2009)

I reckon the tendons in my legs will snap before my chain will !


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## MR_GRUMPY (Aug 21, 2002)

Happened to me once, but it was so long ago, it was a seven speed chain.
.
.
.


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## rkdvsm (Jul 15, 2006)

Sorry for the dumb question, but what exactly is chain snapping? I would guess that it's when your chain just breaks apart at a link.

If that is true then why would someone fall over their handlebars? I would figure that you would just find yourself spinning really fast.


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## brucew (Jun 3, 2006)

I've done it twice. Once it was side plates splitting, the other time the master link gave out.

Both times on my commuter, in March, after a full winter's worth of wear when I was trying to get past salt season before installing a new one.

Of course I prefer to think of it as having to do with the megawatts produced by my massive quads.


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## Oxtox (Aug 16, 2006)

in 45 years of riding, I've broken one chain.


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## tlg (May 11, 2011)

I think Mark Cavendish would be a dead man if chains broke even remotely often.

Mark Cavendish - TKO - YouTube


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## pmf (Feb 23, 2004)

It' happened to me a few times. I carry a small chain tool and an extra master link in my seat bag.


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## JCavilia (Sep 12, 2005)

rkdvsm said:


> Sorry for the dumb question, but what exactly is chain snapping? I would guess that it's when your chain just breaks apart at a link.
> 
> If that is true then why would someone fall over their handlebars? I would figure that you would just find yourself spinning really fast.


You understand correctly how it happens, but not when. It can result in a spectacular crash because it's more likely to happen when the rider is putting maximum force on the chain. That's not when you're seated and spinning, but when you stand up for a sprint or hard climb effort. If the chain breaks, the rider's leg, bearing all his weight, suddenly falls, usually disconnects from the pedal, and everything goes to h*ll as his foot hits the ground. I've seen it happen in races. It is very rare with a properly assembled and maintained chain, as others have noted.


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## tlg (May 11, 2011)

JCavilia said:


> You understand correctly how it happens, but not when. It can result in a spectacular crash because it's more likely to happen when the rider is putting maximum force on the chain. That's not when you're seated and spinning, but when you stand up for a sprint or hard climb effort.


Yup
This position + high speed + max power + broken chain = ugly results


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## Kontact (Apr 1, 2011)

wim said:


> While it does happen, it's really rare for a properly installed and maintained quality chain. The number one cause by far for a chain to "snap" is improper installation, and especially so if it was done with a replacement pin rather than a master link. With 10-speed chains, the replacement pin method margin of error is very small, almost zero.
> 
> I used to do intervals and still ride a bit of track (500-meter TT with a standing start, you can imagine the forces on a chain) and have never had a chain problem that wasn't due to my installation error.


I have installed hundreds of chains with pins. I have never seen a Shimano or Campy pin failure when a new pin is installed in the right direction and with the right tools.


Shimano had a run of chains (Ultegra) several years ago that had some problem and many of them broke. But overall, chains do not break unless hugely abused, twisted or corroded. This is the reason I'm always such a pain when people start talking about recycling SRAM's single use Powerlinks.

A chain will fail if it is put together wrong or damaged, but so will a fork or handlebar - with similarly painful results. But even with all the incompetent home and shop mechanics in the world, chains still have very low failure rates, but it is one of those things that it is worth doing right and not guessing on.


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## AndrwSwitch (May 28, 2009)

I've broken a couple. Reasons were installer error, shifting under load, and shifting under load.

I don't worry about it happening unless I do something along those lines.


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## laffeaux (Dec 12, 2001)

I've broken one chain in 20 years of riding, and it was due to poorly executed (under pressure) shift in the middle of an out-of-the-saddle climb on my mountain bike. Over the years I've seen several others break chains on rides - primarily on mountain bikes, but occasionally on the road - almost always it's been related to shifting under extreme pedal pressure, trying to downshift several cogs at once, and the chain gets out of alignment and comes apart. If you easy off of the pedal pressure slightly during a big downshift it's really unlikely that a chain will break.


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## jmorgan (Apr 13, 2012)

Had a pin come out after about 40 mi, didn't have anything to fix it. I will never use one again, Master links are much easier to deal with.


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## qatarbhoy (Aug 17, 2009)

Kontact said:


> overall, chains do not break unless hugely abused, twisted or corroded. This is the reason I'm always such a pain when people start talking about recycling SRAM's single use Powerlinks.


So , you never re-use them? I rotate chains about every 600-800km on my bikes and re-use the Powerlinks.

I've broken a Dura-Ace chain while MTBing (and repaired it by taking links out and shoving a pin back in, as I didn't have any spare pins: not recommended), but never a road bike chain.


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## Kontact (Apr 1, 2011)

qatarbhoy said:


> So , you never re-use them? I rotate chains about every 600-800km on my bikes and re-use the Powerlinks.
> 
> I've broken a Dura-Ace chain while MTBing (and repaired it by taking links out and shoving a pin back in, as I didn't have any spare pins: not recommended), but never a road bike chain.


I think it is stupid to do anything a manufacturer has specifically told you not to do. Especially when a single point failure of that part will cause a crash - like chains and forks. There is almost always a very good reason for the maker to go to the trouble of making such a statement, and since all link manufacturers don't make an issue of it, I'm inclined to believe that SRAM knows what they're talking about with their product.

I'd recommend "investing" in a Connex link and using it on two or three chains.


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## locustfist (Feb 21, 2009)

In 20 years I've only broken one chain. A 9 speed chain on a 6" travel MTB powering through baby heads.


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## dgeesaman (Jun 9, 2010)

tlg said:


> I think Mark Cavendish would be a dead man if chains broke even remotely often.
> 
> Mark Cavendish - TKO - YouTube


I think Mark Cavendish gets a new chain much sooner than the rest of us. Especially when you consider their entire team effort hinges on one sprinter's sprint.

To the real subject: chains can break. Corrosion, wear, and cumulative miles are major contributors to failure. Engineers refer to this as fatigue failures.

It seems to me that road cyclists fall into two categories: they either replace and service their chain too frequently or they have no concept it will wear or break. I don't particularly agree with either group, but the chance of breakage certainly agrees with those who replace/maintain their chains. 

(IMHO, keeping a mid-priced bike in good shape by replacing wearing items a bit too often is way more practical and reasonable than buying a more expensive bike and neglecting it)

David


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## Ventruck (Mar 9, 2009)

Shifting under sudden sprinting "load" = pretty guaranteed chain snap. My twig self managed to do so/


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## qatarbhoy (Aug 17, 2009)

Kontact said:


> I think it is stupid to do anything a manufacturer has specifically told you not to do. ... since all link manufacturers don't make an issue of it, I'm inclined to believe that SRAM knows what they're talking about with their product.
> 
> I'd recommend "investing" in a Connex link and using it on two or three chains.


Yes, I may do that.


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## tlg (May 11, 2011)

dgeesaman said:


> I think Mark Cavendish gets a new chain much sooner than the rest of us. Especially when you consider their entire team effort hinges on one sprinter's sprint.


So? Even a new chain can break. If you read the posts above, most of the reports of failed chains are due to shifting errors and improperly installed pins.



> To the real subject: chains can break. Corrosion, wear, and cumulative miles are major contributors to failure. Engineers refer to this as fatigue failures.


I think everyone one knows, any highly worn mechanical system is subject to failure. Which I don't believe the OP was asking about but rather snapping due to massive torque on the cranks.


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## wim (Feb 28, 2005)

Kontact said:


> I have installed hundreds of chains with pins. I have never seen a Shimano or Campy pin failure when a new pin is installed in the right direction and with the right tools.


I don't quite get your point. No one here claimed that pins can fail even if installed properly. It's great that you installed hundreds of pins without a single screw-up. I can't make that claim, hence my experience-based warning about improperly installed pins.

I like your "invest" in quotes, by the way. Wonder why the plain but much more truthful "buy" is no longer good enough for some people?


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## Kontact (Apr 1, 2011)

wim said:


> I don't quite get your point. No one here claimed that pins can fail even if installed properly. It's great that you installed hundreds of pins without a single screw-up. I can't make that claim, hence my experience-based warning about improperly installed pins.
> 
> I like your "invest" in quotes, by the way. Wonder why the plain but much more truthful "buy" is no longer good enough for some people?


I wasn't arguing with you, but trying to mitigate the point you're making about pins being much more likely failure point than links - I just don't think the majority of chain failures would be traced back to replacement pins, because it isn't that easy to screw them up. It is just that some people can screw up anything, including a link.

I think it is also important to realize that the many broken MTB chains mentioned in this thread are likely due to forces and use that a road bike will never see. Granny gears and wide ratio cassettes with very slow cadences combine a lot of torque with very high side loads and uneven application of force over uneven ground. Road use is just a lot smoother than that - including sprinting.



Yeah, the "invest" was a joke. $15 for a Connex link will seem like a lot to some people, no matter how much more useful it is than a Powerlink. And nothing we buy bicycle wise is an investment - my bike shorts certainly aren't gaining value every time I plaster them on my naked butt.


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## wim (Feb 28, 2005)

Kontact said:


> It is just that some people can screw up anything, including a link.


Certainly true. Perhaps age has something to do with pin-replacement failures. I can't see well anymore, and the 10/11-speed pins have got to be in there just so. Back in the day, there was some leeway because the pins protruded quite a bit. I think I'll get some stronger glasses and better lighting for my workbench.

Googled around for "invest" a bit and came to the conclusion that advertising copy writers are responsible for it's popularity. It makes sense. If you tell people to "invest" in a $6,000 bicycle instead of "purchasing" it, they might just believe that it will gain value as it ages. Right.


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## gordy748 (Feb 11, 2007)

I broke one once on my fixie, it was a few months after I got it but I think it was because the dodgy shop I used didn't use a master link. I wasn't going fast but still went down, I was trying to turn a 49 x 15 gear pulling away from the lights (lived somewhere flat).

After it was replaced somewhere better, it never broke again.


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## cxwrench (Nov 9, 2004)

jmorgan said:


> Had a pin come out after about 40 mi, didn't have anything to fix it. I will never use one again, Master links are much easier to deal with.


not installed correctly...


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## BigTex_BMC (Dec 30, 2011)

Thanks for the input guys, my mind is now at ease.


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