Adjusting the rear derailleur

[northstar]

does the chain try to ride between gears and have trouble deciding which one it wants to be in? This can be corrected with the barrel adjuster - turn the adjuster out (making it longer) to increase cable tension until the chain is centered on a cog.

This is what is happening. I watched it today as I was riding. It was trying to hop to a lower gear.

[li10up]

I know this post is a little late but watch this video...it is really helpful. I was always scared to do any adjustments on my bike for fear of messing it up even more. After watching this video several times I'm no longer worried...at least not as much. I was able to resolve my shifting problem on my own! And that feels so good not having to rely on the LBS all the time.

http://youtube.com/watch?v=D0Xt_QCHD1U

[indysteel]

li10up, thanks for posting that. That's very helpful.

[Kalidurga]

Another thanks to you, li10up, for that link! I always forget to check YouTube as a source for that sort of thing, and it looks like there's a pretty big assortment of bike maintenance videos posted there. Awesome!

[boy in a kilt]

Your problem is your rear derailleur isn't quite indexed properly.

This is caused by one of three things.

1) You took your wheel out when it was properly adjusted and didn't quite get it back in straight. It happens but unless you have Campy, it's have to be pretty severely out of whack for this to happen.

2) Your stops aren't set right. These are set by the little screws on your derailleur. If they were set right to begin with, it's probably not that.

3) Your derailleur cable stretched or slipped a bit. This is the easiest thing to fix and the first thing I suggest you try. Turn the barrel adjuster that your cable runs through counter clockwise a little bit. If you watch the derailleur while you do this, it should move toward the wheel a little. Play around with it until your derailleur starts to behave.

Also, this site is magnificent:

http://www.parktool.com/repair/byregion.asp

It shows pictures and the tools you'll need.
If you can get your hands on one, Terry has a great manual on how to fix your bike.