I have a 105 nine speed with a triple in the front. I have a problem with the front derailleur that I can't quite adjust right. If I'm going up hill on a somewhat steep grade on the middle chain ring and the next-to-innermost cassette cog, the chain will often jump down to the smallest chain ring even though I didn't shift it. A related problem is that sometimes when I'm shifting from the big chainring top the middle (on an inner cog in the back), the chain will skip the middle chainring and drop to the small one.
Any ideas what I adjustments I need to rectify this problem?