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  1. #1
    Senior Member bennie222's Avatar
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    trouble with sr custom triple crank - chain fallling between rings

    I'm working on a '83 Miyata 610 I picked up and am having trouble with the crankset. I could see that there was a lot of chain damage to the crankset where the chain had dropped between the rings but I though I could figure it out, usually someone just installed a ring backwards. This triple has all three rings held together with the same chainring bolt, it doesn't have the separate attachment for the granny gear.

    Oddly enough, the thing was assembled correctly, but the chain can still fall between the two outermost rings. I tried all sorts of combinations, but ultimately, the middle ring is set so the teeth are 'closer' to the outer ring, and i can't close the gap any more. The chainrings aren't bent.

    I did get it to work by turning the outer chainring around. This moved the teeth closer to the middle ring. I know it's wrong though, because the outer ring has a recession where the chainring bolts should sit and now it's backwards and the bolts don't sit recessed.

    The chain could be the wrong chain, but it really does look like a wider 6 speed chain so I doubt it's the problem.

    Let me know if you all have any ideas or have seen this before. Thanks.
    Last edited by bennie222; 02-21-11 at 09:35 AM.

  2. #2
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    Odds are that the crank dates back to the days of 6 speed when chains were wider. If it's old enough to predate Hyperglide, then the chains wouldn't have the pins peened flush so they'd even wider.

    In any case the separation of the chainrings is related to the width of the chains, and you'd have similar problems using 10s chains on many 8s and 9s cranks. The solution is simple - replace the chain with a wider one. Look for a 5 or 6 speed model. Of course if you have a 7s or more freewheel or cassette you'll need a chain that isn't too wide. Hopefully you can split the difference.

    The alternative is to try to carefully thin the part on the crank spider between the chainrings, but that's a difficult fob with a hand file. If you decide to try that, buy a "one-side-safe" file, so you can preserve the shoulder, and you'll need a caliper to check your work as you go along and make sure all 5 points match.
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  3. #3
    Senior Member bennie222's Avatar
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    Can you suggest a few chains that I can look at that are 'wider'. Thanks.

  4. #4
    coprolite fietsbob's Avatar
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    You may have distorted the chainring with the first jamming of the chain between them.

    Dismantle, and insure that they are flat, checking them against a flat surface.

    You can either buy new ones or try to flatten them out..

    Seek, generically, 5.6.7 'speed' or 3/32" wide chains,

    Or if you re assemble it as a single speed configuration. 1/8"
    Last edited by fietsbob; 02-21-11 at 09:40 AM.

  5. #5
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    Quote Originally Posted by bennie222 View Post
    Can you suggest a few chains that I can look at that are 'wider'. Thanks.
    You didn't say how many speeds on the cassette but judging from the 1983 date I guess it's a 6 speed. So any 5 or 6 speed chain would work. The beauty is that they're cheaper than newer chains and simpler to work with because you cut and splice them by pushing a pin back and forth.

    Here's one possibility but there are plenty of other choices. Note that the pins stick out which will push the chain over so it drops onto the middle ring more readily.

    BTW- as the other poster pointed, you might have warped a chainring, but there's no need to take anything apart to check. Simply turn the crank and watch for horizontal movement in the FD cage.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

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