Hmm... upgrade would help?

[indysteel]

My "industry sources" say the opposite. Even fairly cheap rear derailleurs shifts well because the shifter acts on the unloaded side of the chain. A drivetrain would operate better with a lesser quality RD and a higher quality FD (and crankset). Bikes aren't sold that way due to marketing considerations - the RD catches people's eye and it's model number becomes associated with the whole drivetrain. So put a 105 RD on a bike with otherwise cheaper components and it sells better at a given price point.

Nevertheless, some words of advice for carriesn. Put your bike in it's lowest gear (inside rear cog, smallest chainring) and observe the gap between the chain and the inside of the front derailleur plate. It should be only 0.5 mm on a 10-speed system, up to 1 mm on a 9-speed system. If it's greater than that, take it back to your LBS for a better adjustment. Also, observe the angle of the outer plate on the derailleur. It should be parallel to the chainrings (comparing to the largest chainring is easiest). In terms of usage, keep track on what rear cog the chain was on when a FD shift results in a dropped chain. If it's only certain cogs, you could learn to avoid a FD shift in those cogs (not ideal and not foolproof, but may save some headaches). It could be that upgrading to Ultegra would make you very happy.

Interesting...thank you for sharing that. I'm long thought that the RD was the better thing to upgrade in terms of performance. I'm curious as to why and when the RD became the "defining" feauture of the drivetrain.

[Ana]

This may be an unnecessary question but when you shift from granny to second, what gear are on in on the back? I ride a small bike so the cage length is short and so my shifting greatly depends upon what gear combination I'm in.

[aicabsolut]

Try readjusting the limits. But first, make sure the derailleur was properly installed in terms of height and angle (assuming it's clamp and not braze-on, which has very limited angle adjustment). Look at ParkTools' website for help. Compacts can be finicky, and so very precise installation of the front derailleur is required to get both 1) smooth shifting, and 2) minimal to no front derailleur rub when in extreme gears (helped by the trim in the shifter). If moving the clamp, be sure not to over-torque on the seat post!

Then, adjust the limits. Adjust high limit first (with next to no tension on the cable) then low limit.

Once the limits are set, check the indexing (cable tension).

If you still have problems, you may need to be extra careful about what rear gear you're in when shifting down in front. I find that if I'm nearer the middle of the cassette to about 4 from the top, the shifts are the best with my compact (and 105 or Ultegra FDs). Too high on the cassette, and it gets worse. So be sure to shift rings first, then rear cogs.

If all else fails, get a chain guard. (google them or look at something like tech pages on cyclingnews about what the pros use on their Roubaix bikes). It's a little guard that clamps on under the derailleur that keeps the chain from bouncing inward too far. Instead, it hits the guard and that guides it onto the little ring instead of letting it fall too far to the inside.