Bicycle Mechanics - Chain question compatibility question- warning, may be a dumb question.

Hi,

I just bought a shimano 105 CN-5701 chain for use with my 5603(triple) crank. I just discovered, however, that the back of the chain box says "For Double Chainring only". Can you tell me why this would be? How does a chain know how many chainrings you have? Do I REALLY need to send it back and find a new one? What would the new part number be?

Thanks so much for any help :)

Even Shimano's tech guys don't have the answer to that. When I was looking to buy a replacement chain for my Ultegta triple 10-speed bike I also considered a 5700 or 6700 chain until I saw the "double chainring only" lable so I bought a CN-6600. Then I called Shimano to find out why and the basic reply I got was "I dunno".

Since then I've seen other postings that say the 5700/6700 chains work ok on triples

thanks for the info...though i'd be more comforted if i found one of those posts you mention. i'll keep searching.

Would it be length? I would think the closeness of the cassette would be the controlling dimension but maybe a triple needs a slightly longer chain than a double to account for the extra range of movement for the crank?

i don't think so...caus the biggest chainring and sprocket is what dictates the chain length...AND, the chain comes longer than you need anyway so you can trim it.

i don't think so...caus the biggest chainring and sprocket is what dictates the chain length...AND, the chain comes longer than you need anyway so you can trim it.
not exactly. The biggest chainring and sprocket *and* the deraillers. And deraillers on triples have more capacity (called long-cage or something). I guess the derailler cage may make a bit of difference here.

And out of curiousity - I searched some more and found what looks like the answer. That post said:
The CN-7900 and CN-6700 will not work on a triple because the chain does not allow enough lateral movement.
This makes sense, as Shimano has been trying to improve their chains recently. They also enhanced it with asymmetric form this time.
So I assume the 5700 series chain will follow the above and also have a supposedly restricted lateral movement.

not exactly. The biggest chainring and sprocket *and* the deraillers. And deraillers on triples have more capacity (called long-cage or something). I guess the derailler cage may make a bit of difference here.

And out of curiousity - I searched some more and found what looks like the answer. That post said:
The CN-7900 and CN-6700 will not work on a triple because the chain does not allow enough lateral movement.
This makes sense, as Shimano has been trying to improve their chains recently. They also enhanced it with asymmetric form this time.
So I assume the 5700 series chain will follow the above and also have a supposedly restricted lateral movement.
That doesn't hold water. The "lateral movement" required to shift over a 10-speed cassette is more than any crank, double or triple, requires.