Thursday, February 18, 2010

78 Shimano Ultegra Chain Failure

New "Equipment Misbehavior". A reader from the Netherlands (who wishes not to be named) alerted me to his concern that lately, a large batch of Shimano Ultegra chains (CN 6700) have been breaking with use. These chains are narrow and lightweight, meant for performance riders. I'm not aware of what its roller diameter, plate width etc are. Can anyone help us here?

Anyway, so he was personally riding a steep cobbled climb last Thursday when his chain, 700 kms old, broke on one side of a link. Interestingly, he was able to get home and install a spare new 6700 chain as replacement. Well, guess what. A little after 7 hours and 220kms of riding over Saturday and Sunday, that chain also happened to fail. That's not a good thing to happen to someone who's stranded in the middle of nowhere.

He decided to call Shimano Europe and found their response to his problem as quite rude. In his own words :

"Shimano is still denying the problems, but many people have problems with the 6700 chains. I spoke to someone from Shimano Europe on the phone this morning, which wasn't pleasing since he was quite rude. For me it is not about the money, but all about the risk. The question is if someone is going to crash because of these breaking chains, when and how many crashes are there are going to be? Often there is quite a lot of difference in customer support between Europe and North America. For example Zipp seems to have a great service in the States, but in the Benelux it simply sucks. But the attitude of Shimano seems to be bad everywhere. "

He examined the first chain he broke and found 15 different cracks all over the place. The second chain he broke had 11. He's having the chains sent to another company, who will then X-ray examine them for deficiencies. As and when I get any more news on that, I will post it here.

Notice the interesting manner of crack formation at the two ends of the chain

Now roller chains are reliable over a wide range of temperature conditions. So if the Netherlands has had a really bad weather this year in terms of winter and salt on the roads, should it matter if the chain is well maintained? The individual who contacted me reported that he regularly washes his chain in plain hot water to get rid of salt.

As to the question of whether he applies any other chemicals to the chain for cleaning, I do not know. Shimano does protect their bottom to some extent by calling out the following in their technical instructions.

For chains to avoid breaking in fatigue, the operator has to restrict stresses to those below the corrected endurance limit for the material. The total load in a chain is a sum of the tangential driving force, centrifugal tension in chain and the tension in the chain due to sagging.

But even still, a chain should NEVER break. The only evidence of deterioration in a chain should be elongation due to steady wear. But that usually happens only after 1000-2000 hours of usage in well lubricated chains. They should be pretty reliable otherwise. For a new Shimano chain to break in 7 hours may point to something unassured in its design/manufacturing.

Have any of you experienced similar problems with these chains as well as Shimano's deteriorating customer service?


Campagnolo 11 Speed Chain Failure

* * *


  1. Andy Gullick5:40 PM

    Awesome blog!! This is a keeper!

  2. To say a chain should never break is a bit much. If we know the conditions it is used under, then ideally, yes a chain will wear (elongate) but not break. Poor cleaning methods (or lack thereof) and most especially poor shifting habits both risk damaging bicycle chains leading to eventual breakage. This is user error, and it's up to the user to adjust their habits and/or replacement intervals to avoid such an issue.

    Only if entire batches of chains are breaking for a variety of users can we really say there is a QC/design issue.

  3. "Poor cleaning methods (or lack thereof) and most especially poor shifting habits both risk damaging bicycle chains leading to eventual breakage."


    This is really moot. Define poor cleaning method and poor shifting habits. Not lubricating a chain is only going to lead to wear and stretching. Occasional cleaning should not cause fatigue failure in a chain, it's not made of biscuit. The narrow chain will only break if its improperly put together, as I had an experience very similar to that (see Compagnolo chain failure post linked at the end). I know lots of people who have properly installed chains, don't give a damn about them and it has gone on to live a year of life or more. Ofcouse, it'll wear but it won't break.

    As a side note, what would slightly interesting to know is the quality of the water used to clean the chain. I didn't really hear the water is the Netherlands is excessively salty but what do I know?

  4. You don't believe that mashing the chain up and down multiple gears under load can twist and break links?

    I'm not claiming to know that the user in question with the 6700 chains is doing this, but it is the cause of almost all broken chains.

  5. Jeff :

    Again, it can fail IF the connecting pin or link is improperly installed. If it is correctly installed, it should not fail. I have experience analyzing chains...chains are designed so that the maximum tensile stresses do not exceed the corrected fatigue strength of the material, like I wrote in the post. If its not designed this way, it is poor design. Chain design is dictated by a set of ANSI or ISO standards...
    The chain can also fail due to wear but in this case, 2 days of riding will not cause wear. I can't speak for the user but I don't think anyone would be excessively stupid to run an improperly adjusted chain and "mash" it all over the place.

  6. Anonymous7:50 PM

    answer to why chain broke seems simple. these things have to be heat treated, mostly case hardening. classic case of poor heat treatment. i would ask the manufacturer to check their process control, check depth of case hardening in links.

  7. Just learned that the user would use water with car-wash or soap to clean. , if that's of any help to discussion. Is chain degreaser specially made to be mild pH? Would anyone know?

    @Anon : The radiographic examination would tell us if that were true.

  8. Andy Gullick8:34 PM

    Keep in mind Europe was especially cold this winter, as news stories had it. I wonder if that has to do anything with the breakage. Awesome discussion btw! This is why I want to read this blog.

  9. I've seen the exact same break pattern on a SRAM chain. I occurred after I soaked the chain for a prolonged period in Simple Green.

    I would ride two chains, one would soak, then I'd swap (about weekly). Both chains has this kind of cracking.

    I would look at the cleaner, first, before stating that the chains are poorly designed.

  10. I'll wait for the the owner to take part in discussion instead of trying to speak for him. I still don't see how cleaning solution can be linked to a new chain breaking in two days. Whats the need to clean with soap a new chain? :)

  11. Ron: Lot's of people strip the grease off the Shimano Chain before using them in order to apply their preferred lube.
    This has been well documented for years in Velonews about how excessive use of chemicals like Simple Green can cause issues like this person has experienced, and James noted.

    If that is not the root cause, I would then do as Anon 7:50 suggests and inspect the material through a simple hardness test followed by a tension test using one outer plate as if it were a "dog bone".
    I would then compare the average failure of these two chains to maybe six other chains from Shimano, SRAM, & KMC.
    If the results come show the material hardness and/or tensile strength of the two bad Shimano Chains as significantly lower, I would then go perform a materials test of them also.

    More to the point - An X-Ray really won't show any more useful info that what has already been visually observed and is simply a waste of time.
    If the cstomer really wants to prove Shimano has a flaw in their manufacturing process, then what I have discribed is the easiest, and fastest way to produce truely valid data.
    - Ryan

  12. I've been a professional mechanic at a couple different bike shops for 5 years now. I recently installed a Dura Ace 7900 chain on a new bike with new chainrings and a new cassette and went for a ride. The shifting seemed a bit funny, but I attributed it to having a new bike, cable and housing wear, salt all over the roads, etc. On my second ride, I was just riding along (and yes, I know how much pain that term brings to those that fix run down, ill-treated bikes for a living, but I was literally pedaling 50 watts with a cadence of around 60 on the side of a road waiting for my companions to pass through a stoplight) when my chain broke exactly like this chain shown here. I actually ditched the chain in a gas station trashcan in a moment of frustration while I was pushed a few miles to the nearest bike shop, so I don't have it for warranty/inspection, but my anecdotal evidence is such that the new Shimano chain design isn't quite perfect yet.

  13. Jacob : Interesting. The chain had cracks in the same fashion as shown in the pics? And is the Dura Ace chain the same in design as Ultegra?

    Ryan : Well, perhaps things can go with Simple Green (I like the fact that it's biodegradable though). However, I'm pretty sure user told me he uses just a plain soap solution with hot water. I'm also thinking this may be a heat treatment related flaw. The user has already sent in the chains so too late I guess for implementing what you suggest. It will be interesting to see what comes out of the X-rays.

  14. To me chains are not the right place to try to save weight. As chains get thinner and lighter, more problems will occur. I think more research should be done with belt or cable type drives in place of chains. Just my opinion.

  15. Chris : Agreed. The mentality in the cycling industry is save weight, save weight..! Taking 50 grams off a chain is going to do zilch for you. As it is, chains are light and centrifugal effects are smaller compared to those in heavy machinery. Those paper thin link plates are worrying. When I said chains should never fail, I was actually talking about normal, utilitarian stuff that joe public uses, not high performance schwag. Hey good to have you back commenting!

  16. I'm not a technical professional, so I can't comment on materials engineering and the forces, etc. However, it seems ridiculous to me that Shimano still has not conclusively solved the problem with Simple Green and other of these kinds of solvents. Because people have been cleaning chains with these solvents for many years (many of them shimano chains); it's not a case of a few people choosing to use these products.

    Shimano should have changed the treatment of their chains; worked with pedros or whoever to re-formulate their solvent; released a notice telling customers and shops to quit using the stuff and give them an alternative (ie. petrochemical solvents). In my view, as one of the biggest component manufacturers they have a responsibility to do this, even though anecdotally other chain makes have also been affected.

  17. Anonymous12:28 PM


    More proof of the near state of perfection..hun?


  18. Jacob: I have never met a bike mechanic anywhere in the US, Canada, Europe, or Asia who would ever throw away a relatively new $70 chain just because it broke.
    Typically most would either try to see what happened, and maybe they could fix it, or use it on another bike, or call the company for a warranty.
    You sir by throwing away one of the most expensive chains on the market, seems to be paid far too much; which makes me quite skeptical on your assertion of being a Pro Mechanic.

    Chris:There is a reason over a hundred years of research and manufacturing keeps validating the use of a chain as the optimal method in transferring energy from the Chainwheel to the Rear Cog.
    Go look it up.

    Ron: Basic Physics can refute your opinion on chain weight as valid. Weather you want to agree that the amount of accumulated energy needed to move a chain at 90 rpm for 4~6 hours is significant is up to you.
    Just don't try to say the deign parameters of a 10 spd chain is the same as some basic chain on a commuter bike which hasen't chainged much, with regards to weight, in probably 20 years.

    Victor: Simple Green works just fine if you use it as advised, but if you use the stuff as James did which Simple Green had not suggested AND Shimano and had not recommended the result will be as James experienced.
    So, how can a product be engineered optimally and also account for every jackass idea some customer has to maintain it?

  19. Anon : The utilitarian bicycle chain, as we have seen all these years, is trustworthy and does the job. To work in offset conditions in all kinds of muck and weather is a testament to its durability. Funny you mention it..the bush roller chain was first introduced specifically as a solution for bicycles in the 1800's by Hans Renold. Combined with the derailleur, we have had it for over 100 years so if was imperfect, it'd not have lasted that long. Need we say more? Problem with today's designs are that it is increasingly catering to a market which is completely irrational about possession of light weight parts, hence the designs themselves are sketchy to begin with. I'm not saying that is the case with this chain, just in general. This discussion however doesn't mean we have a necessity for hubless, and spokeless wheels, if you're the same chap from the previous discussion on Yale's design.

  20. Ryan : This is getting slightly hilarious, no? Okay, I would love for you to show me calculations on the % difference of energy savings running a chain of 250 grams and one of 220 grams at the same speed, i.e 90-100 RPM in a BICYCLE. I personally believe its a miniscule amount. And if you think like an engineer, you wouldn't stress on it that much, if not neglect it outright. If you think like a physicist, you would sit and lose sleep over such small numbers. Each person comes with a different mentality. :)

  21. Ryan: I would argue that 'optimal engineering' would account for reasonable ways to maintain the item. Soaking a dirty chain in solvent doesnt seem so outrageous to me that the manufacturer can't anticipate it -we're not talk about soaking a chain in moonshine, sasquatch urine or some other exotic thing.

    I would certainly be happy to pay more or bear with an extra bit of weight for a chain engineered to resist these solvents.

  22. Jenny4:26 PM

    What is the rationale behind Shimano chains not working with a biodegradable solvents? Does it eat away the metal? I dont understand it.

  23. Trackasaurus4:47 PM

    Have to agree with Ron. Not much of
    the bike in the last 2 decades has made a 'significant' difference in
    cycling enjoyment. New advancements these days come from marketeers, not engineers. They consequently break. Sad.

  24. The User6:32 PM

    I am the used that broke these 2 chains. To make a few things clear:
    I always remove the grease on a new chain with some teflon spray and cloth.
    The chain is not clean, since the weather is horrible there is no way to keep a chain clean and well lubricated for a 6 hour training ride. Result is it becomes dirty... But a chain doesn't break because it is dirty. I could have applied degreaser before making the pictures, but what's the point?

    I never broke a chain before (used Sram, KMC, Connex and Campa). I cleaned and lubricated these chains just as all the chains I had before and we have had bad weather before in the Netherlands ;-)

    But the main issue is I am not the only one breaking these chains. Some team mates also broke their chains. A test rider of a Dutch magazine destroyed 2 6700 chains in 1000 km on a CX bike. And many others also have the same issues. Shimano tries to tell everyone they are the first with this problem. That is not the attitude I expect from such a large company. They should take their responsibility and take those chains back and replace them with proper ones. I was 'lucky' only half of the links broke. But it is a matter of time till a serious accident will happen. And I am afraid it won't be one accident, when Shimano doesn't call those chains back.


    pH of Simple Green is 9.5. That is alkaline. It is not super alkaline (i.e. 14), but it is not 7 either.

    Soaking a chain for a week in a pH 9 solution will probably etch it. If it comes out that non-smooth dull grey colour & texture, it means you are etching it. If it has already started to crack, I assume this would make it worse.

    Want to make chains work with all sorts of solvents, detergents and surfactants? It needs to be chemically resistant. That means stainless steel. I don't know enough to know if that is practical.

  26. Anonymous10:16 PM


    I am the same anon from the Yale post & never suggested hubless/spokeless was a solution to anything..I think it was a waste of aluminum.

    I just found it ironic that we were discussing the shortcomings of CHAINS/derailleurs...& your next entry was about chain failures.

    As I said before the Porsche 911 is a very functional automobile (albeit long of tooth @ 45+ years), however its longevity doesn't speak to it being the best solution, just one that engendered a following.

    My contention is chains are a very compromised design which have always been troublesome...the recent weight-weenie fetish has only exacerbated them. Are you suggesting that because chains were invented 200 years that somehow demonstrates some superior that standard candles were invented 1000's of years ago...are they a superior light source?

    I think it is premature to blame these failures on weight reduction before there is an investigation.

  27. Been MTB'ing for 15 years now and I have never broken a chain. Replaced probably a dozen of them but I don't think they are a compromised design, works pretty well.

  28. It is no cleaning issue. Shimano has/had some problems with their chains. They all fail in that manner. I don't know if they sort it out by now. Buy Campy chains ;-)

  29. My experience years ago when Regina was leaving the chain business, someone offered me a stack of chains in those small cardboard boxes. I used one that cracked and failed even though it was the old style with a small pin over-stand on both sides, old roller width and side plate thickness... old heavy derailleur chains of the kind they made
    for many years reliably.

    I inspected more of these chains before using them and found they all had crack initiation, probably from improper heat treatment or an
    improper alloy. In any event, that was my experience with chain
    failure and I haven't had any since with Shimano chains, but then I don't use flush side narrow chains for my 7-speed gear clusters.

    Jobst Brandt

  30. He-Who-Shall-Not-Be-Named-Because-He-Posted-Anonymously stated that
    Simple Green could weaken bike chains and cause them to crack at the outer plate hole for the pins. IIRC the mechanism was hydrogen embrittlement. I have no way of knowing if this was factually correct or was hot air (hot electrons?).

    Simple Green seems to claim their "Extreme Simple Green" product
    protects against hydrogen embrittlement:

    "Extreme Simple Green¹s safety upon aircraft materials and precision cleaning surfaces comes from a combination of proven anti-corrosion agents. A time tested coupling agent allows these to work together to battle corrosion and hydrogen embrittlement. These same qualities make Extreme Simple Green safe to put through pressure washing equipment, rack wash systems, dip tanks and parts washers, without any equipment

  31. Ken Matheson4:02 AM

    more gears = thinner side plates = more breakages. How many broken 6, 7 and 8 speed chains broke? For me it started with 9's.

  32. The User5:21 AM

    @Ken, I have ridden 10 speed chains for years and never broke a single one, including on my CX bike.
    10 speed chains are reliable except these Shimano chains.

  33. The User: Honestly, I think you hav been providing Shimano very good feedback and the likely issue is the the heat treatment process involved with the component that is affected.
    That said, I wonder if their reluctance is the lack of a clear mfg dating system on the chain so they are not able ot attain the batch affected and so further data needs to be collected before they can create a clear recall?

  34. Hey great post.

    I don't like Shimano chains as they have a history of failing at the worst time.

    Finishline USA has three different methods on Youtube for cleaning chains. Some are more enviromentally friendly then others.

  35. I've broken a Shimano 10 speed chain (don't remember which model). It had more than a couple of days of use on it, but I remember I was still disappointed in its short life (somewhere south of 1000 miles, IIRC).

  36. I stopped using Shimano chains about twenty years ago when it became apparent that breakage of the Uniglide chains I used at the time was a recurrent problem.

    I have worked at five different bike shops over the span of many
    years, and none of them ever sold Shimano chains except by special
    request. Sedis/Sachs/SRAM chains were always the default (and very
    reliable). Their reliability does not seem to have been significantly
    affected by added shift-enhancing features or reduction in size over
    that time.

  37. Really enjoyed this discussion folks. Keep it up!

  38. I've just broken a Shimano Ultegra 6700 chain after 2500km. I've kept it well lubricated, never cross-chain excessively (and never with force). It has broken in the exact same manner as in the image shown. I've never broken a chain before and usually swap them out after 10,000km.

  39. Hey Roger,

    Sorry to hear that. Do you have any pictures? Would be interesting to see.


  41. Roger,

    Seems like there's been a string of failures in the same way. Its probably a heat treatment issue like was said before. We have formed a good database of images and discussion. I couldn't be happier for safety's sake. Thanks!

  42. The Ultegra 6700 chain on my girlfriend's bike has just suffered a really similar failure, with the outer plates cracking and splitting apart in exactly the same way. It's relatively new, has about 400 miles on it at most, and has never been degreased, let alone immersed in the stuff for 9 days.

  43. I had a shimano (xtr level) chain go pop on me 10 days ago causing a catastrophic crash which landed me in hospital with a badly broken collarbone and a bunch of black bruises.

    The chain had about 500 km's on it but as it was my commute bike my wife who is still very rough on her gear changing (no anticipation whatsoever, just cruncho cruncho crunch), had been using the bike for shorter rides we had been taking together which made me realise I was perhaps the one to blame.

    Anyway after an on bike clean with kero to get grease off and re-grease followed by a brief inspection, (joining link fine, no kinks in chain laterally) i'd gone 30 km's on it and it broke on third stroke of the pedals while clipped in and standing up taking off from a set of lights.

    Before I realised what had happened I was picking my sorry carcass up from amidst swerving traffic and felt my collarbone moving around quite a bit. Ouch! I thought I'd been clipped by a car bringing my back wheel off the tar and putting me over the bars but as I picked up my bike I saw the chain sitting about a meter back and so I left it there to rot!!!!!

    1. I rode about 2500 hard mtb kays on the previous Sram chain and had no issues. (That chain went west when I put my rear derailer through some spokes after braking a rear hanger) 2. I had only just got back into commuting and upping my time on the bike again and was no way near as strong as I had been when training on the Sram chain. 3. I don't feel I was putting too much into the chain but I was definitely giving the pedals some stick (flat road on mtb slicks); but nothing near what I'd put the Sram through though, not even close (think grueling hill intervals at full throttle).

    Metal in my shoulder and a wife who is going to quickly learn all about anticipating gear changes before she dumps a thumb full again.

    P.S: I believe this could have been avoided with a thorough check before placing my faith in it wholeheartedly. And don't worry, I've not taken to the wife to pass the buck :-) But; I will definitely go back to Sram chains and leave the Shimano at the crash site where I believe it belongs.

    Thanks for reading my story, Cheers Michael.

  44. Bob Ding9:04 AM

    I have just replaced my Ultegra 6700 chain after it broke 3 times. On close inspection about 10 more cracks were visible. My Ultegra chainset is supposed to only use Ultegra chains but there is no way I'm buying another Ultegra chain until this problem is sorted.

  45. Anonymous1:13 PM

    For days I have been reading and looking for Shimano Ultegra Chain Failure and wow I have no idea that in the web were so many blogs related to generic viagra, but anyways, thanks for sharing your inputs, they are really helpful.
    Have a nice day

  46. I have a Ultregra chain that broke after less than 1000 miles. When I took the chain off I was surprised to see cracks like in the photo above on many links. There barely any stretch to the chain. I take pretty care of my bike but don't use simple green or anything other than simple solvents like kerosene, and rarely at that. I work with metal so I also know about metal cracking. It seems to me that the links are not hardened properly and that the pins are so tight and probably a different alloy that when there is a great temperature change (like when taking your bike out of a hot car and riding with a sudden down pour, that the hardened links shrink around the pins and crack. The cracks did not suggest cracking under chain tension; extreme tension (like riding up a hill) is probably merely the last straw.
    I'm going to do some test and see. I'd urge all Shimano chain users to check carefully for cracks.

  47. Well, I tested that chain- heated it, cooled it, stressed a good section until it pulled apart on a 12 ton press-but I could not replicate all of those cracks radiating form the pins on the side of the chain with slot cut into it. I bet they were there when I bought it - stress cracks from the pin installing procedure or heat treating. If I had $70 to throw away I'd but a new one and put it under a lens. Counter intuitive that the chain is asymmetrical like that- the stresses can't act equally on each side. Maybe I'll send it to Shimano.

  48. Anonymous10:07 AM

    My Ultegra chain also broke. I replaced the link and noticed skipping again immediately. I looked down and noticed another broken link. After walking home, I took the chain off and counted 36 broken links. That is not a typo. 36. All of the failures were similar to the ones posted above. The chain had less than 2 months of use.

  49. Anonymous2:34 AM

    Same issue, rode approx 1000 miles, noticed skipping after a hard hill set and chain broke. Bike shop fixed with new link, next ride skipping again, one link cracked.

    bike shop replaced and sent to shimano. Same as pictures in main story.

  50. Anonymous7:34 PM

    I had 2 brand new Ultegra 6700 chains break the first after approx 300 miles the second after 500 or so. The second was installed by a shop. Seems to me to be a problem. I noticed the same thing with the chain skipping at a certain spot and then a ride later breaking. I am now goint to be checking all chains more closely. With only this many miles on them it was not a cleaning issue.

  51. My CN-6700 let go at about 1500 km. I am a low-
    power rider. The chain was well maintained, cleaned with standard petroleum solvents and lubricated often. The rear derailleur had just been adjusted and was slightly out of index at the time. The failed link was 30 links from the connection. The failure was of the slotted-side plate similar to the photos at the top of this page. Front - back orientation was correct per Shimano instructions.

    I cleaned the chain and inspected it with magnification without dye penetrant. No other cracked plates were evident. Several scratches were present on the front (non-slotted) plates but none had propagated cracks.

    The chain was purchased from a large retailer in the USA in February 2010.

  52. Anonymous6:12 PM

    After reading this blog item, I've been watching my Ultegra 6700 chain very closely. I hit 4000 miles and it showed no "stretch" on any of my chain wear gauges. Incredibly, on the day before I was planning on changing it, I started feeling a "click" in the drive train. I examined the chain and saw that one side plate had broken.

    What I find interesting is that the chain was so tough in terms of normal wear (no stretch after 4000 miles) but eventually failed in the manner that many others had with very little use.

  53. Not happy with shimano chains. A few years back I had problems with one chain in particular that kept dropping pins, e.g. the plates would separate from the pins. I had consecutive issues with later chains aswell, prompting me to upgrade the whole drivetrain to 9 speed, to see if it made a difference.

    It did, no more split pins, however the chains wore quickly - I'd be lucky to get more than 1500km from a chain.

    There is a brand called 'KMC' - they make chains that are far superior to shimano's offerings, for example I replaced the shimano HG with the KMC X9.93 - so far I've done over 2,000km on the chain and it is showing no signs of wear, with less than .25% stretch.

    I recently purchased a road bike which came with a shimano 105 chain that has already exceeded .5% stretch with only 300km of use, all of which was light use whilst getting used to the bike.

    KMC also make a similar offering, the X10SL, which is highly regarded and (as little I know) does not have any such reports of failure. Even so, given the X9.93's brilliant performance I would sooner recommend the X10.93 offering instead.

  54. Anonymous6:25 PM

    I had a shimano Ultegra 6700 chain break on me today in a very similar way as seen in the picture. It's done about 300 - 400km. The broken link got caught in the rear mech and destroyed it, throwing it into the rear wheel and doing damage there too. Luckily I wasn't going too fast at the time but still got dumped on the floor. My poor opinion of Shimano 10 speed chains has been reinforced by this latest incident. I've run Sram chains on other bikes without incident and I don't think I'll be buying a shimano chain anytime soon.

  55. I just had my ultegra 6700 chain snap and it has multiple cracks just as the picture shows. i figured it was my fault, but after searching this is pretty common problem.

  56. Just had my Ultegra 6700 chain break. About 100-200 hours of usage though. Broke in exactly the same way pictured above. I was able to ride home, but scrapped the chain.

    I've never broken a chain before, so I was pretty surprised. I'll be going back to KMC numbers from now on (a lot nicer to install too...)

  57. Anonymous12:20 PM

    I bought a KMC DX10-SC chain to replace the OEM Ultegra chain that wore out ("stretched"). This chain failed in the exact same manner as the Ultegra chains previously posted, but this was after almost 1500 miles. I didn't notice any cracks in other plates, but I'll have to take a closer look after reading this blog.

  58. Anonymous1:50 AM

    The inside plate of a Shimano 6700 series chain fractured, separated from the link pin, hooked the derailleur cage, and pulled the derailleur backward destroying the derailleur, and ripping the derailleur hanger and dropout from the frame. A second failure, of a separate 6700 chain, occurred on another bike within a week this past December 2010. Shimano now appears to be marketing a revised chain designated CN-6701.

  59. I am currently using a Shimano Ultegra 6700 chain.
    It has been degreased and cleaned regularly. Plus Lube applied. I have just cleaned it after 700 miles again. There are two cracks on two separate chain links. The exact same as shown in the pictures above. It will be going into the bin !!

  60. Anonymous6:39 PM

    I'm following up my post from 12:20PM. My KMC DX10-SC chain that snapped did NOT have any other suspect links, or at least I could find no cracks. I did contact KMC and after asking for chain photos and how I maintained the chain, they asked for the old chain back and replaced it with an X10.93 chain. Hopefully they're doing some failure analysis.

  61. Just had my 10speed Ultegra 6750 chain break this morning (7 May 2010), looks exactly like the first picture above. Broke while climbing a very short but very steep hill, about 60% grade to get up onto a bridge. The broken outer chain plate grabbed the derailer and pulled it into the back wheel damaging two spokes and snapping off the hanger of my 2011 Look 566.

    Chain is about 10 weeks old with about 500Km of use

  62. Hello, I was able to ride home, but scrapped the chain.

  63. Cheapyx11:05 AM

    I found this discussion as I had exactly the same problem with my HG 6700 chains. First one broke after 400 miles relatively easy riding with many sideplates broken in a similar pattern as shown on the photos. I am neither strong nor heavy and I didnt degrease the chain at all. Just lubricated and cleaned it. My second chain lasted maybe 500 miles. Most of them on a roll. I am convinced there is something wrong with the chain design. Won't buy that one again for sure.

  64. I have seen this exact failure twice this summer.

  65. Anonymous5:55 AM

    Just my 2 cents: Idealy chains should never break, but some people are luckier than others. My luck is breaking chains, and that is how I replace them. Within my riding history (competitive and touring), going back to 1994, Shimano chains have been the worst, so this post is no suprise. The classical mode of failure is a 90 degree slice of the outer link (links) (bisector along the load axis). With this particular image above, it seems that somebody miscalculated the press fit tolerance or criping force of the die (also possibly metalugrical variations, meaning that the pins are harder than originally thought) causing the plates to crack.

  66. Amazing!I also wish him good luck to defend his gold medal. I like to share it with all my friends and hope they will also encourage him.
    organic seo service|

  67. Anonymous11:13 AM

    I had a 6701 chain break on me in a slightly different manner - two links, about 8 inches apart, separated from the pins a bit - enough to snag the rear derailleur and pull it into my rear wheel, trashing it and the hanger and chipping the frame and wheel. The chain had less than 500 miles on it. I highly doubt it was an install problem, as a very good bike shop did it (though they are going to examine it for me when I can get to the shop). The fact that it was in two different parts of the chain seems weird - the rear derailleur had started skipping shortly before it happened, which makes me think it was the chain that broke first and caused the other damage. The chain was shifting fine when there was no load on it when I looked at the side of the road, then when going very slowly up a steep hill in the middle of the rear cluster it just snapped.

  68. I recently came across your article and have been reading along.
    I want to express my admiration of your writing skill and ability to make readers read from the beginning to the end

  69. I really enjoy simply reading all of your weblogs. Simply wanted to inform
    you that you have people like me who appreciate your work. Definitely a great
    post. Hats off to you! The information that you have provided is very helpful.

  70. Brilliant post and useful information…I think this is what I read somewhere…but I don’t know with your experience

  71. Hello, I am very happy to read your blog. This is another fantastic blog post what I have read.

    find doctor list

  72. I have bookmark your blog site and will be without doubt coming back.I appreciate all your work and also providing a lot vital tricks for your readers.

  73. Anonymous10:09 AM

    Be advised that this chain has an inner and outer side. The outer link plates with the slot in them are supposed to face toward the inside of the bike. I don't think that is the cause of these cracks though, but putting the chain on wrong could put the the slotted link plates under more stress than they should be.

  74. The outer link plates with the slot in them are supposed to face toward the inside of the bike.

  75. The only evidence of deterioration in a chain should be elongation due to steady wear.

  76. That's not a good thing to happen to someone who's stranded in the middle of nowhere.

  77. Anonymous11:06 AM

    I fitted a Shimano Altegra chain exactly as recommended, the chain snapped while going up a steep hill after only 150km.I will never buy Shimano chains again

  78. same thing on my Felt AR4 which came with the 6700 - in less than 1500 miles saw the cracked link while cleaning the chain. LBS replaced it with a 6600. just replaced the PC1030 that came on my 2010 F3 with the 6600 - much quieter now. 6600 does not have the cutout - i figure it wil be stronger.


Thank you. I read every single comment.