Measuring Chain Stretch
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Thread: Measuring Chain Stretch

  1. #1
    Senior Member elime's Avatar
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    Measuring Chain Stretch

    And how much is OK?

    I took my very Cow Mt. dusty chain and hung it so it was straight up and down. I then took a tape measure and aligned the 9" mark with a rivet near the top and duct taped it together. (Pictures rotated horizontal to make them easy to read.) On a 4XX chain the rivets are exactly 1/2" apart.

    Chain1.jpg

    I then looked 18" down the tape measure (at the 27"mark) and found the rivets and the half inch marks no longer aligned. The rivet that belonged at the 27" mark was now at the 27 1/8" spot.

    Chain2.jpg

    Looking 36" down the tape (at the 45" mark) the rivet was 1/4" past where it belonged.

    Chain3.jpg

    So how much stretch is OK?

    A little internet research says .006" per link (and I guess they mean for each rivet) is the max. There are 73 rivets in 36 inches. 73 X .006 = .438" = 7/16" which means I can use this chain until it stretches another 3/16 inches per 36" of chain.

    There are approx. 24,000 miles on the chain now. By my calculations it should last until 42,000 miles -- which is a figure I find very hard to believe.
    Last edited by elime; 05-07-2014 at 10:09 AM.
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    Senior Member admiral's Avatar
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    This will be helpful, thanks.
    Hidden Content A ride in the woods helps me relax and release tension. The fact I'm dragging a body should be entirely irrelevant?

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    Senior Member jbfla's Avatar
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    Quote Originally Posted by elime View Post
    And how much is OK?

    There are approx. 24,000 miles on the chain now. By my calculations it should last until 42,000 miles -- which is a figure I find very hard to believe.
    Excellent info. I remember seeing the way to measure the stretch of the Yamaha chain, but can't remember where.

    A guy on the Triumph forum got a documented 40,000 miles on a Bonneville x-ring chain. I can get about 20,000 miles on an o-ring chain before I feel the need to change it, even if it looks OK.

    What comes to mind is that the wear may not be linear. As the chain wears, it may wear more quickly as the tolerances increase.

    jb
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    Senior Member RockyTFS's Avatar
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    Technically, a chain does not stretch, it wears. The effect of wear on the rollers and rivets is that the chain gets longer. The side plates do not change. The test for excessive wear is to try and lift one link off the rear sprocket at the middle. If you can lift one end of that link to, or beyond, the top of the tooth, the chain is worn beyond a safe amount. This is how chains get thrown, usually at max speed, and it's not a pretty sight. IMO, trying to see just how many miles you can get out of your chain is NOT worth the risk of it coming off at 60 on a highway!

    42,000 miles on a dirt bike chain? Not HARD to believe, IMPOSSIBLE to believe! My guess is that by the above technique your chain is ready for replacement, and so are the sprockets. (Both chain wear and sprocket wear contribute to the above test.)

    And yes, jbfla is right, the wear is often not linear, so perform the test in several places.
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  6. #5
    Senior Member jbfla's Avatar
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    Quote Originally Posted by elime View Post
    And how much is OK?
    Here's how much...according to the manual:



    jb
    2018 Triumph Street Twin..............2016 CB500F
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    Senior Member RockyTFS's Avatar
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    Sorry...half a tooth......, not the whole tooth and nothing but the tooth......
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    Senior Member elime's Avatar
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    Quote Originally Posted by RockyTFS View Post
    Sorry...half a tooth......, not the whole tooth and nothing but the tooth......
    Not to worry -- all is forgiven!

    But next time hit the edit button and go back and change what you said. That way it is like it never happened.
    Long live the internal combustion engine!

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    Senior Member RockyTFS's Avatar
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    Then I wouldn't have been able to make a silly pun....
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  10. #9
    Senior Member elime's Avatar
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    I have been told that a stretched chain causes the rollers to ride higher on the teeth causing them to bend over making the sprocket look like a tsunami warning sign.

    When I installed this chain I also installed new sprockets. The front, rear, and chain have been together for the 24K or so miles.

    On the front sprocket the teeth are worn but standing straight up. (Excuse the flash rust -- I just washed the bike.)

    P5051316a.jpg

    The rear sprocket looks good to me.

    P5051314.JPG

    And the pull test. I still think it is less than 1/2 a tooth.

    P5061323.JPGP5061321.JPG
    Long live the internal combustion engine!

  11. #10
    Senior Member RockyTFS's Avatar
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    Quote Originally Posted by elime View Post
    .....

    When I installed this chain I also installed new sprockets. The front, rear, and chain have been together for the 24K or so miles.
    Is that an O-ring chain? If not, that's really good mileage! You must clean and lube it often. (Just because you have an O-ring chain doesn't mean you shouldn't clean and lube it often.)
    Rocky
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