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  1. #1
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    Loose chain = stretched?

    Hey all. Recently, my chain has gotten very loose. When pedaling at a good clip it is pinging off my bar with my pedal rhythm.

    Is it possible that I have "stretched" (I know this isn't technically correct) my chain?

    There are a few nice hills near me that I have frequented. One is the first hill I've had to hop off on. Near the top I am basically keeping myself from rolling backwards gaining a 1/2 rotation with a concentrated "umph".

    Or is the thought that my back wheel has merely slid forward, causing the slack?

  2. #2
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    is it a new chain? chains do stretch.

  3. #3
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    here's a good site about chains and maintenance.

    http://www.sheldonbrown.com/chains.html

  4. #4
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    I've been riding it for a bit over a year commuting.

    So one hill (not as vicious as the one near me now) on my old route was a constant every day thing. The new hill (bought a new house) is an occasional thing.

  5. #5
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    It might be time for a new chain. Do you know how to take the slack out?

  6. #6
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    Measure the stretch and you will know the correct answer for what to do

    Taken from Sheldon Brown's site:
    Measuring Chain Wear

    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 exactly in the middle 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.

    This gives a direct measurement of the wear to the chain, and an indirect measurement of the wear to the sprockets:

    * 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.

  7. #7
    edo
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    Chains dont stretch...they do wear however...the little pins (rivets) wear, & that effectively makes the rollers able to move further apart. The side plates dont stretch though.

    Its probably that your wheel has moved forward in the dropout/slider due to your awesome power up your big hill.

  8. #8
    awesome
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    chain might be worn and/or you need to realign the wheel if you have track ends, or check the ebb

  9. #9
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    Quote Originally Posted by edo
    Chains dont stretch...they do wear however...the little pins (rivets) wear, & that effectively makes the rollers able to move further apart. The side plates dont stretch though.
    although i do agree partially (the rollers do wear for sure and i check my chain with a chain guage that takes this into account)... if chain's don't stretch at all why does a bike god like sheldon advise using the ruler trick to measure chain wear? that shouldn't work at all if the side plates don't stretch.

  10. #10
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    Quote Originally Posted by max-a-mill
    although i do agree partially (the rollers do wear for sure and i check my chain with a chain guage that takes this into account)... if chain's don't stretch at all why does a bike god like sheldon advise using the ruler trick to measure chain wear? that shouldn't work at all if the side plates don't stretch.
    Read Sheldon's page again and look at the picture of the chain rivet that is worn down where the next chain link was connected. That wear pattern allows the center of the hole in the next link to rotate around a position that is past the center of the pin. Now the ends of those two links are further apart, which explains why a ruler can be used to measure chain "stretch".

    edit: I doubt the side plates could really ever stretch. Normal steel has a yield strength of somewhere above 50,000 pounds/sq in, which means that stress less than that may cause temporary and slight elongation but no permanent change to the steel. I don't know what the cross-sectional area of a side plate is, but even if we say it is only 1/16 of a square inche, that would require over 3000 lbs of force to permanently stretch the steel
    Last edited by boomn; 09-17-2009 at 09:46 AM.

  11. #11
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    Quote Originally Posted by max-a-mill
    if chain's don't stretch at all why does a bike god like sheldon advise using the ruler trick to measure chain wear? that shouldn't work at all if the side plates don't stretch.
    Look at your chain and note that the side plates are not directly connected to each other -- they are connected by the pins and the rollers. Summing up the wear on the many rollers in a chain allows it to lengthen significantly without actually stretching the side plates. If you were to take a logging chain and where the links touch you were to file off some metal, the chain would lengthen without actually stretching the side of the chain -- make sense? Well, at least it makes sense to me...
    "The plural of anecdote is not data." -- Attributed to various people in a variety of forms, but always worth remembering...

  12. #12
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    Quote Originally Posted by PeT
    Look at your chain and note that the side plates are not directly connected to each other -- they are connected by the pins and the rollers. Summing up the wear on the many rollers in a chain allows it to lengthen significantly without actually stretching the side plates. If you were to take a logging chain and where the links touch you were to file off some metal, the chain would lengthen without actually stretching the side of the chain -- make sense? Well, at least it makes sense to me...
    yeah actually, that does make perfect sense!

  13. #13
    one chain, two sprockets
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    Nah, you are all wrong - only Sheldon is correct. If you measure greater than 12 inches center-to-center, your chain has stretched.

    When measuring the distance between externally visible rivets, it does not matter how much internal wear the rivet has, since this has no effect on the external center-to-center distance on the rivets.

    Make sense?

    Tom P.

  14. #14
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    Quote Originally Posted by one piece crank
    Nah, you are all wrong - only Sheldon is correct. If you measure greater than 12 inches center-to-center, your chain has stretched.

    When measuring the distance between externally visible rivets, it does not matter how much internal wear the rivet has, since this has no effect on the external center-to-center distance on the rivets.

    Make sense?

    Tom P.
    did you really read Sheldon's page?

    The rivet wear sure does affect the distance to the next rivet. Maybe I can do a cool paint drawing later!

  15. #15
    Sup
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    the distance in my cad drawing shows "one piece crank" is correct
    there is no change in distance is between the rivits
    the links are all the same length
    it is the slop in the holes the rivits run through that let the chain get longer

    Slow Joe
    Last edited by Burnt-Orange; 12-11-2012 at 12:49 PM.

  16. #16
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    I don't think the question really got answered. Yes, you should check the chain, and replace it if it is more than 1/8 inch longer than 12 inches between pins. Yes, since it sounds like you have horizontal dropouts, your wheel has probably moved forward, and you should loosen the axle fixing bolts, slide the axle back again until the (new) chain is snug, and retighten. You should be able to push the chain down about 1/2 centimeter, or else it is probably too tight. The real test is that the chain should move smoothly with respect to the cog and chainring, with no binding. Both types of loosening happen to me all the time.

  17. #17
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    can anybody write that down in cm. how many cm should new chain measurement be and how many worn one?
    need more bikes...

  18. #18
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    Quote Originally Posted by enio
    can anybody write that down in cm. how many cm should new chain measurement be and how many worn one?
    here you go

  19. #19
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    This is always a silly argument. The chain doesn't stretch, it just gets longer with wear.
    Just one more rep and I get the toaster!

  20. #20
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    "Chains dont stretch...they do wear however"

    OK, you're right. They don't stretch. I shouldn't have said it stretches. I meant that it gets longer with wear. Either way... it is getting longer ain't it?

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