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Old 06-15-06, 04:19 PM   #1
shipinabottle
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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...
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Old 06-15-06, 04:24 PM   #2
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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).
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Old 06-15-06, 07:47 PM   #3
shipinabottle
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So is this something I can figure out myself?
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Old 06-15-06, 07:56 PM   #4
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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.
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Old 06-16-06, 06:04 AM   #5
72grandprix
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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.
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Old 06-16-06, 06:29 AM   #6
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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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