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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 03-30-11, 07:06 PM   #1
intelli78
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Chain hopping back and forth on rear cogs *video*

Hello, all,

New to bike maintenance but want to learn. Recently bought a 2008 Schwinn Fastback Comp cheap. Has a Dura Ace rear derailer and cassette, but I'm having some problems with autoshifting -- not only up, but down, too. In fact, it even hops back and forth with the wheels in the air. When riding, it feels like chain slippage. Occurs exclusively on one or two of the middle cogs, though the teeth are in great condition.

Would love some help figuring this out. Video here: http://www.youtube.com/watch?v=n-7M33xtw-w

Thanks!
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Old 03-30-11, 07:28 PM   #2
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Start from ground zero with that

1) Check hanger bolts - secure
2) Check wheel properly secured - on ground undo and redo QR
3) Check hanger is aligned
4) Begin your normal H/L limit adjustments
5) B-screw
6) Tension

Other things to consider - is it 10 speed?

1) Is the cassette loose?
2) Lockring tight?

Derailleur worn out?
Cable + Housng?

....
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Old 03-30-11, 07:58 PM   #3
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Follow the operators advice, and check his entire list. But before you do the entire drill, use the cable (trim) adjuster to get the derailleur centered on a sprocket as best you can.

Search "how to adjust a derailleur" to find some tutorials. there are video or text and pictures. Review a few until you're comfortable with the basics then give it your best shot.
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Old 03-30-11, 08:20 PM   #4
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looks like derailleur is not moving but chain is. check cassette for bent tooth.
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Old 03-31-11, 01:26 AM   #5
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Check out this Park Tool - rear derailleur adjustment site.

Easiest to try is the cable-tension adjustment before getting deeper. To determine if you need to loosen or tighten your cable, adjust your lever into the highest-gear cog (smallest teeth count). Spin it a couple times to make sure the chain is all the way down. Then spin the crank and click the lever up ONE click.

Does the chain move up one gear? If it clatters but doesn't shift up, tighten the cable a quarter-turn.
If it moves up one gear then rubs on the 3rd gear, cable is too tight and loosen it a quarter-turn.

Repeat as necessary.
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Old 03-31-11, 09:30 AM   #6
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Looks like what my Shimano does right before the cable breaks and is frayed only hanging on by a few strands.
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Old 04-01-11, 04:59 PM   #7
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Thanks to everyone for the replies. I adjusted the derailer to no avail - then replaced the cable and all was good.
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Old 04-01-11, 05:50 PM   #8
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What kind of chain do you have?

The Fastback Comp is a 9 speed bike and you have 10 gears out back. Are you running a 9-speed or 10-speed chain?
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