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?



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