I've not tried those 770 shifters with a 105 derailleur, but the claim by Shimano is that the two will be incompatible. Does your FD-R770 need to be replaced?...or is this a type of upgrade? I ask because the 770 is a high quality derailleur.
Actually you are right again! The 770 does at least cost more than the 105 a few places I checked. The reason I asked is because the bike I just purchased was advertised to come with the 105 5700. It works fine so I will leave well enough alone.
That FD is a flat-bar road FD. It allows you to use flat-bar/MTB front shifter with larger road chainrings. Don't replace it with a regular road FD, like the 105, or its cable-pull ratio won't match to your shifter.
Originally Posted by slopvehicle
Not wearing a helmet makes me more aware of my surroundings. I find myself anticipating the hardness of concrete 50 or 100 feet in front of me, it's almost a zen-like connection between my face and the pavement.
FWIW, in your comparison, you shouldn't really judge the quality difference by the item price. I suspect that Shimano sells countless more 5700 FDs than R770 FDs, and either a higher price or lower profit will come with the smaller production. Regardless, the R770 I had was functionally and cosmetically equal to my Ultegra.