Rear Derailer Frustration

[jack1]

hey folks,

About 2 weeks ago my rear derailer started doing the odd stuff. I have to double shift to for it to go into a LOW (easier) gear. Sometimes it will jump one high gear and go straight to high another. It will often shift to a HIGHER gear by itself (every time I hit a hill, it seems). All the stuff that drives one crazy.

I've watch the video 6 times. Travel screws are set. B screw doesn't seem to be too far off to make a difference. I put on a new cable. Lubed the chain and the derailer. No difference.

I notice when I sit on the bike and look down, the top jockey wheel is not lined up with the gear it's in- usually sitting lower- so I adjusted the barrel, but then it has the same issues on a different gear.

It seems to get more off center as it goes to higher (smaller gears).

Here is what I am considering:

the hanger is bent.
cable housing needs to be replaced
derailer is wearing out (over 4K on it)
derailer needs a serious cleaning (I've lubed it a ton but have never pulled it off to do so).

Thought? Advise?

Thanks in advance.

[DaveM]

(05-24-2010, 05:28 PM)jack1 Wrote:  It seems to get more off center as it goes to higher

That definitely could be caused by a bent hanger or derailleur. It sounds like it got worse fairly suddenly which means it's probably not a wear or dirt issue. Housing could be an issue if there is a bad break somewhere. But that should be fairly obvious.

[jack1]

Bent hanger was confirmed by LBS.

Thanks for the input.

[mike46]

I had the same problem when I put on a new chain - so I put on a new derailer as well it works better but still fiddling trying to get that "Sweet" change spot !

[xerxes]

(06-13-2010, 01:00 AM)mike46 Wrote:  I had the same problem when I put on a new chain - so I put on a new derailer as well it works better but still fiddling trying to get that "Sweet" change spot !

I recently fitted a new chain only to find that it skipped on one of the cassette sprockets. I had left old chain on too long and it was quite badly worn. When I inspected the cassette I noticed that one sprocket, obviously the one most used, had also badly worn to accommodate the old stretched chain, to such an extent that the new chain no longer engages it with it properly and skips. So I've had to replace the cassette as well. I also bought a chain wear indicator tool, so I'll be keeping a closer eye on chain wear from now on.

In any case, it might be worth having a good look at the cassette for any badly worn sprockets. Especially the smaller ones with fewer teeth as the load is more concentrated on these and they wear quickest.