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Thread: Bike always upshifting

  1. #1
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    Default Bike always upshifting

    Has this ever happened to you? (cue informercial music).

    Lately, as I'm pedaling up the trail overpasses at National on the MVT, my bike will decide to shift to a higher gear, causing me much consternation and not just a little injury in the seat area (the chain seems to jump out of line as well, causing a few rounds of free spinning pedals).

    I notice my shifters (old Panasonic DX-2000) move a bit while I'm pedaling, but the actual shifting only takes place when I'm putting a lot of force into the pedaling (up hills, etc).

    Any ideas on what's going on here and how I might be able to fix it?

  2. #2
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    Mark Blacknell would probably recommend a slight adjustment of the barrel adjuster on the rear derailleur. Or maybe time for new cables?

  3. #3
    DismalScientist is offline I really need to log off the internet and go for a ride.
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    Tighten the bolt on the shifter. I assume this is a friction shifter and is not indexed. Even if it is indexed, tighten the bolt. Sometime the bolts have a little swing out piece of wire that allows you to do this without a screwdriver.

  4. #4
    baiskeli's Avatar
    baiskeli is offline I really need to log off the internet and go for a ride.
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    Do you hear the chain rubbing?

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    Mine do that whenever the shifter cable or chain need replacing. Check both, replace what's needed.

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    If the derailleur doesn't actually move, it's probably a worn chain or cassette.

  7. #7
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    Default Cable sticking

    If your shifter's cable is routed underneath the bottom bracket, it might be getting hung up on some gunk down there. Check to see if the cable is moving freely. If not, clean the area and lube the chain so that it slides freely.

  8. #8
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    Thanks for all the replies!

    I fiddled with the bolt and looked at the cables. Apparently, all I needed to do was look, because the problem has stopped... for now. Not sure what I did, but it seems fixed.

    I'm guessing the cables need a replacement anyway. Chain seems fine, no rubbing; derailleurs working fine as well.

    If it starts again (or the chain explodes or something) I'll apply the suggestions here en force.

    Thanks!

  9. #9
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    Mine started doing the exact same thing in October. It would skip or magically shift itself under heavy load such as that of going up a hill. I quite literally feel your pain. It was the cable exhibiting symptoms of being 10 years old, rusty, and stretching. It can't hold back that kind of force when it stretches instead of holding.

  10. #10
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    Update!

    This morning (2/3) it started again, but this time with the other gear set (front). I have a feeling the temperatures have an effect on the cables (contracting in cold weather?). We'll see how the ride home goes.

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