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  1. #1
    Junior Member
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    Chain falls between chainrings

    I am fixing up a Trek 260 Mountain Track. Its about 15 years old, and has a triple chainring that is spot welded or something similar (as opposed to chainring bolts). Bottom line is that you can't take it apart. Rear is 6 speed. It was shifting poorly, I finally realized what the problem is: Spacing between chainrings seems more than normal. The chain actually drops between the teeth and gets stuck there before it gets a chance to properly engage on them. My theory is that the original chain(not on the bike now) might have been wider. I tried a new SRAM 6-7-8 chain, that was no help. Adjustments, lubrication, no change. Sometimes shifting occurs OK, but usually not.
    Hope someone can help. The bike is for sale, and needs to function properly.

    Thank you everyone,

    Mike

  2. #2
    Elitist Troglodyte DMF's Avatar
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    Are you using indexed shifters? Does usually fall into one gap, or both equally?
    Stupidity got us into this mess - why can't it get us out?

    - Will Rogers

  3. #3
    Junior Member
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    Yes, the shifters are the twist grip kind, indexed.
    There is more trouble going back and forth from the big ring to the middle ring. Little ring/Middle ring less problematic.

  4. #4
    Senior Member Bill Kapaun's Avatar
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    About the only thing I would suggest is buy the cheapest Wal Mart chain they have and hope it's "crummy" enough.

  5. #5
    Elitist Troglodyte DMF's Avatar
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    Could be a mis-adjusted FD.

    Could be a worn crankset - the pins that pick up the chain on a shift have to be relatively sharp or the chain slips off. Got another crank you can try?
    Stupidity got us into this mess - why can't it get us out?

    - Will Rogers

  6. #6
    Junior Member
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    I adjusted the FD every which way before it dawned on me that the chain was simply falling between the rings. I don't have any spare parts other than chains. The bike is up for sale, I have a solid buyer, but not if it doesn't shift correctly. I'm going to contact Trek, maybe they can help.

  7. #7
    Elitist Troglodyte DMF's Avatar
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    On a 15 year old bike? Wishful thinking.

    A chainring is a wear part like a tire and is supposed to be changed when worn out. There are inexpensive ones, btw.
    Stupidity got us into this mess - why can't it get us out?

    - Will Rogers

  8. #8
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    Yup, go to LBS or local bike co op and get a used right crank with rings. Shoud be able to find one for $5-$10

  9. #9
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    Thanks to everyone for your ideas. The solution was a surprise: the chainrings are cheap stamped steel. Over time, what with shifting, stuck chains, and general abuse, the big ring was simply bent outward along its circumference. Several well placed blows with a dead blow hammer did the trick.

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