ghost shifting

[wackyjacky1]

Does the skipping (since the bike isn't trying to jump into other cogs, what you described is called "skipping") happen more on certain cogs? If so, which ones? Does it make a difference if you have shifted down into the problem cog or up?

Now that I've looked at that Sheldon Brown info, I can say that I have experienced both skipping and autoshifting. What happened this afternoon was skipping.

It only seems to happen when I'm in the smallest chainring, am in the 3rd or 4th cog, and am grinding up a hill. The skip or autoshift will occur well after my last gear change.

I don't know why the LBS messed with your front derailleur. That seems to have just gotten your shifting even more screwed up.

He fixed it today. Front derailleur is fine now.

Then, once you're in the small ring, see if the chain is rubbing the cage.

Had a lot of chain rub after he messed with the front derailleur, but it was fine after he readjusted it today.

is it slow (a hesitation) to shift in either direction (inward or outward)?

Shifting is nice and crisp. The problem only occurs under load, as when I'm going up a hill. It doesn't happen during or right after a shift. It happens well after the last shift, making it totally unexpected when it does occur!

Your advice is sure appreciated!

[DebW]

Quite often you'll get more skipping with a new chain and old cassette. We'll typically replace the chain, then ride the bike to check for skipping under load, and replace the cassette if necessary.

[aicabsolut]

Quite often you'll get more skipping with a new chain and old cassette. We'll typically replace the chain, then ride the bike to check for skipping under load, and replace the cassette if necessary.

Yeah, if it's shifting fine and then you run into problems under load, it's likely your cassette. You might also want to take some WD40 and really lube up where the cables run underneath your bottom bracket as well as inside your shifters. That ought to get rid of any unnecessary friction on the cables that could cause the autoshift to occur when the frame flexes. You might also want to get the shop to check your rear derailleur and derailleur hangar. Make sure the hangar isn't bent. Finally, if you *still* have problems, make sure there isn't a lot of lateral play in the derailleur indicating that it's getting worn out and needs overhauled or replaced.