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  1. #1
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    Chain stretch question -

    Snapped a chain yesterday taking off from a light. Not fun, but no hurt other than a walk back to my shop to have a new chain installed. One of the pins separated from an outer plate and when my mechanic looked at it, he was sort of surprised. It was a Shimano CN-6701. He measured the chain stretch with a tool and sort of chuckled that it was certainly worn out.

    The chain had been on for a little over 2800 miles of daily, but mellow, use. Here is my question, using a measuring stick (1 foot), at what stretch would you consider a chain to be marginal enough to replace?

  2. #2
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    Give a man a fish, teach a man to fish, yada yada yada

    "bicycle chain stretch" - Yahoo! Search Results

    The standard way to measure chain wear is with a ruler or steel tape measure. This can be done without removing the chain from the bicycle. The normal technique is to measure a one-foot length, placing an inch mark of the ruler at the side of one rivet, then looking at the corresponding rivet 12 complete links away. On a new, unworn chain, this rivet will also line up exactly with an inch mark. With a worn chain, the rivet will be past the inch mark. [For accurate measurement, the chain should be held under some tension -- either on the bicycle, or hanging vertically. -- John Allen]
    This gives a direct measurement of the wear to the chain, and an indirect measurement of the wear to the sprockets. In English measurement:
    •If the rivet is less than 1/16" past the mark, all is well.
    •If the rivet is 1/16" past the mark, you should replace the chain, but the sprockets are probably undamaged.
    •If the rivet is 1/8" past the mark, you have left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you replace a chain at the 1/8" point, without replacing the sprockets, it may run OK and not skip, but the worn sprockets will cause the new chain to wear much faster than it should, until it catches up with the wear state of the sprockets.
    •If the rivet is past the 1/8" mark, a new chain will almost certainly skip on the worn sprockets, especially the smaller ones.

  3. #3
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    Chains don't stretch! They do elongate, however. The above guide is ideal for measuring elongation. Almost ALL chain checker tools will show a brand new chain showing significant wear.
    My carbon footprint has cleats

  4. #4
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    That chain should not have worn out after such little miles. You're are probably not cleaning and relubing your chain enough, and/or using a wax based lube.

  5. #5
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    Quote Originally Posted by froze View Post
    That chain should not have worn out after such little miles. You're are probably not cleaning and relubing your chain enough, and/or using a wax based lube.
    Kind of thinking the same thing about the life of the chain. I figured I should get 5000 or so, but I am not sure with these 10 speed chains. They are "thinner" and so I might be thinking old school.

    I was using a "dry lube" that left a wax like film behind. I think that may have been the problem. Not sure why the chain actually snapped. A pin pulled from one of the plates. It is not so much a chain elongation issue. The mechanic checked out the cogs and he did not see any sort of wear to speak of.

    Also, what are some of the lubes that you guys use? My mechanic suggested I try Rock "n" Roll. It is basically a dry lube. We have a lot of sand on our roads as I am close to the beach.

  6. #6
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    Quote Originally Posted by froze View Post
    That chain should not have worn out after such little miles. You're are probably not cleaning and relubing your chain enough, and/or using a wax based lube.
    2800 miles for a 10 speed chain is pretty decent IME

  7. #7
    RoadBikeReview Member
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    Quote Originally Posted by klmmicro View Post
    Kind of thinking the same thing about the life of the chain. I figured I should get 5000 or so, but I am not sure with these 10 speed chains. They are "thinner" and so I might be thinking old school.

    I was using a "dry lube" that left a wax like film behind. I think that may have been the problem. Not sure why the chain actually snapped. A pin pulled from one of the plates. It is not so much a chain elongation issue. The mechanic checked out the cogs and he did not see any sort of wear to speak of.

    Also, what are some of the lubes that you guys use? My mechanic suggested I try Rock "n" Roll. It is basically a dry lube. We have a lot of sand on our roads as I am close to the beach.
    I've never used Rock N Roll though heard it was good stuff, I'm just not sure it's any better then other dry lube out there. I had two favorite dry lubes, one is Finish Line Teflon Dry, and the other...a bit odd but it works great called Tiodize Speed Skate Lube which can be found at Skate shops. I had a bike shop in Bakersfield CA that sold skates and boards and they used this stuff on all their chains and I thought it worked a tiny bit better then the Finish Line Teflon Dry in the sense it kept the chain a tad cleaner. All dry lubes go on wet and then you have to let them set for 8 hours to dry, I always waited 24 hours.

    Wax is not a good lube, before I got a newer bike with a narrow chain, my wider chains would last 15 to 16 thousand miles on a dry teflon lube, on wax they lasted about 6k miles, I get about 8 to 10,000 miles on my newer narrow chains using Speed Skate Lube.

    Why your's broke, it could have been a weak link, or could have been improper gear selection. Never put a chain in the smallest gear ring (front gears) and have the chain on the 3 smallest rear gears, and vice a versa, never put the chain on the largest ring gear and have the chain on the largest 3 rear gears. This is called cross chaining and it puts too much side to side stress on the chain which these newer narrower chains are too fragile to handle and will cause the chain to wear out faster too.

  8. #8
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    Rock and roll gold is the best stuff I've ever used, but it is not exactly dry, nevertheless, amazing stuff. Highly recommend if you follow the directions and wipe your chain after each ride.

  9. #9
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    It sounds like Chain L is similar to Rock And Roll. I use Chain-L on my touring bike because it will take wet weather better then a dry lube, and you have to wipe it down after every ride as well. Chain-L claims you don't have to clean and relube it for 700 miles...but I'm always skeptical of claims like that, but I have found that I can go 500 miles and no problems, but at that point is when I get a bit weary of the claims and clean the chain and relube.

    With dry lubes like the ones I listed earlier I can go about 200 miles without cleaning and relubing.

    I may be a bit over on the cleaning part but grit will destroy a chain fast, when I lived in the desert with blowing sand presenting problems, I would clean and relube after every 100 miles and sometimes after every ride if the wind kicked up, but I don't that problem any more in Indiana.

  10. #10
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    Spend the 5 bucks and get the Park Tool "Go/No Go" chain checker. It'll take any doubt out of the equation.

    My cheap shimano chain lasted 2000 kms and it was done (.75% wear), where as my ultegra chain is still going strong after over 3000kms not not even at .5% yet.

    Park Tool Co. » CC-3.2 : Chain Wear Indicator : Chain

  11. #11
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    A ruler is the best method for determining chain elongation. Chain measuring tools like Parks, Pro-Gold, etc. read more elongation than there actually is because they add roller wear in twice, and roller wear is irrelevant in the first place. I've actually spoken with manufacturers of these measuring devices and they concur!

    Shops love these chain measuring devices because the get to sell and install three times as many chains as they would if they simply used a ruler. .

  12. #12
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    Quote Originally Posted by looigi View Post
    A ruler is the best method for determining chain elongation. Chain measuring tools like Parks, Pro-Gold, etc. read more elongation than there actually is because they add roller wear in twice, and roller wear is irrelevant in the first place. I've actually spoken with manufacturers of these measuring devices and they concur!

    Shops love these chain measuring devices because the get to sell and install three times as many chains as they would if they simply used a ruler. .
    +1.

    A good metal ruler is the way to go. Those chain checkers are pretty much worthless, in my experience.

  13. #13
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    I snapped a Shimano chain a few years ago. I think it was installer error.

    If I actually wanted to snap a chain, though, I could probably do it by shifting under heavy load, especially the front. I've done a couple of mountain bike chains that way. Apparently it took me twice to learn.

  14. #14
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    Quote Originally Posted by froze View Post
    It sounds like Chain L is similar to Rock And Roll. I use Chain-L on my touring bike because it will take wet weather better then a dry lube, and you have to wipe it down after every ride as well. Chain-L claims you don't have to clean and relube it for 700 miles...but I'm always skeptical of claims like that, but I have found that I can go 500 miles and no problems, but at that point is when I get a bit weary of the claims and clean the chain and relube.....
    I have no idea what Rock n Roll is like. To me, ChainL smells a lot like gear oil and is thick like chainsaw bar oil. Definitely nothing like the other bike-specific lubes I've used over the years which are more like thin motor oil.

    I am using ChainL this season for the first time, and I have found that it does last 700 miles or close to it (+ or -) I don't keep super accurate track, but I know I have documented 600 miles on my commuter plus several 15+ mile additional rides. The chain has just recently become a little noisy.

    ANyway... as far as how clean it stays. I found that it requires a good exterior cleaning three times, after that it pretty much stays as clean as any other lube I've ever used:

    Good wipe down with mineral spirits-dampened rag after initial lube
    Same after first ride or two
    Same after another 2 -3 rides.

    This actually isn't much different than the way I treat regular oil lube, one or two wipe-down's after application. After that, the exterior stays pretty gunk free, like I said, about like any other lube I've used. I'm not a super clean chain freak though.

    Another disclaimer: I tend to avoid riding in the rain, hardly ever do it. I do ride about 10%of my commute on gravel.
    Last edited by Camilo; 10-20-2011 at 04:31 PM.

  15. #15
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    a correction...

    Quote Originally Posted by Camilo View Post
    •If the rivet is 1/8" past the mark, you have left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you replace a chain at the 1/8" point, without replacing the sprockets, it may run OK and not skip, but the worn sprockets will cause the new chain to wear much faster than it should, until it catches up with the wear state of the sprockets.
    On common misconception is the idea that worn cogs accelerate chain wear. That is totally false. The chain merely rides higher up on the worn teeth. That has no effect on the chain's wear. The opposite is not true. A worn chain concentrates more of the load on the last few teeth engaged and will accelerate cog wear. In the extreme, a chain worn to 1.5-2.0% elongation can break teeth or skip when the point of contact finally goes over the top of a tooth. That type of chain skip is entirely different than a new chain used on worn cogs, which will also skip. New-chain skip will often go away if you can tolerate the problem until the chain has a few hundred miles of use. You can also use a new chain with a new cassette for a few hindred miles and then put an old cassette back on the bike and have none of the previous chain skipping problem.

    Also, the smaller cogs might be more likely to skip, but it depends on the terrain that you're riding. Riding about 12 miles of mountain and hill climbing on typical 50 mile rides, my 19 and 21T cogs were the most worn and first to skip.

  16. #16
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    Forensics

    Quote Originally Posted by klmmicro View Post
    Not sure why the chain actually snapped. A pin pulled from one of the plates.
    It may be too late now as the chain is probably out of your hands and in a dumpster someplace, but any time a pin pulls out of a side plate, you should check to see if it was the "installation pin" that was used to put the chain together. If that is the one that pulled out, then it was an installation error. If it was just some random pin then you either had somehow damaged the chain or your chain was defective.

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