Setup of Ultegra Front Derailleur with Compact Crankset
I purchased a road bike in 2008 with full Shimano Ultegra drivetrain and shifters. Before riding the bike, I swapped out the standard crankset to install the compact Ultegra version. After installation, I figured that I should probably 1) shorten the length of the chain, and 2) lower the front derailleur to get it closer to the compact rings. However, I have ridden the bike for nearly 2,000 miles and the shifting has been fine (except maybe the trim feature, read on...).
Last weekend, I decided to lower the front derailleur to the position shown on the (still) attached factory guide. I tried to avoid rotating the derailleur, only changing the vertical position. Naturally, I had to release and reset the shifter cable in this process. Now I have a couple of issues.
Issue #1 — I am getting chain rub against the front derailleur at extreme ends of the shifting range (both the smallest cog and the largest cog), but not in-between. This didn't happen before the derailleur was lowered. Is there a "special" way of setting up this combination, i.e., standard derailleur with compact crank? Should it be higher than normal?
Issue #2 — I am no expert on this front shifter. When I first got the bike, I found that there is "trim" position on the front derailleur where, once you shift to the big ring you can press the second lever (as if you were going to shift to the smaller ring) to move the derailleur inward slightly. I assume that this would be a better position when using the smaller cogs. It bothered me a bit though, because to actually shift to the small ring would require two shifts: one press would simply trim the front derailleur and a second press would trigger the shift to the smaller ring.
After I lowered the derailleur and reset the shifter cable, I found that the trim feature actually worked much better! If I pushed the lever partially, it would trim the derailleur and if I pushed the lever fully, it would shift to the smaller ring. I imagine that is way it is supposed to operate when properly adjusted. In an attempt to eliminate the chain rub, I tried several adjustments and found that the trim feature could be completely lost with some adjustments. So my question is, how does one go about setting up this shifter to maintain/optimize both the shifting and the trim features?