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  1. #1
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    Unwanted gear shifting?

    I'm a teen and know basically nothing about bike mechanics and repair, so I wanted to throw this question out.
    My problem is... Just recently, the pedals on my new (used) bike have started shifting forward (as if I were changing a gear) when I don't touch the gear control at all. I don't actually end up in a new gear, but it's pretty annoying. Right now it's only when I'm in my top (or hardest gear), but I don't know- it might spread. I was using my dad's bike before this and the problem was even worse.
    Is there some simple solution to this?
    Or do I just ruin every bike I seem to ride?

    p.s. when responding, remember i might not know the exact name of any parts you might refer to...

  2. #2
    Senior Member barba's Avatar
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    The cable tension to the rear derailleur have likely stretched a bit and the chain is skipping a bit because the RD is out of alignment. This web page will have directions on how to adjust the derailleur: http://www.parktool.com/repair/readhowto.asp?id=64

    Also check out this one: http://sheldonbrown.com/autoshift.html

    The other possibility is that the frame is flexing a little under heavy loads (this used to happen on old steel bikes that had a little flex in them and have the cable routed under the bottom bracket).

  3. #3
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    So is this something I can figure out myself?

  4. #4
    Senior Member barba's Avatar
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    Yes. Follow the directions carefully and you can do it. It will likely be a very cheap adjustment at a shop, however. If you do take it in, ask them to show you how to do the adjustment.

  5. #5
    nyc
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    another funky thing that i discovered is that the teeth on the highest gear in the rear sprocket began to hook as it wore down. I had this problem constantly when I snapped my chain and needed a new one. The chain and the teeth wore at the same rate so the new chain was simply not used to the hooking.

  6. #6
    Senior Member godspiral's Avatar
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    Quote Originally Posted by shipinabottle
    My problem is... Just recently, the pedals on my new (used) bike have started shifting forward (as if I were changing a gear) when I don't touch the gear control at all. I don't actually end up in a new gear,
    sounds like your chain is slipping over the cogs.-- if the gears are not changing. Back cogs and chain could be too worn out, and need replacement.

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