Originally Posted by
cubewheels
You can "ghost pedal" at half the pedal stroke, beginning at the top stroke of your favorite pedaling leg. This will make a complete shift (to the next cog) with an unloaded drivetrain in just a fraction of a second.
They teach this stuff in GCN in youtube. Still works a charm with my humble bottom end Tourney mech!
You do that for a rear cog shift. However, making a front chainring change requires a surge and soft pedal. IE an unexpected pitch in the road that requires a rapid big to little change or a little to big change (while still on the climb) to crest and motor away while everyone else is still climbing behind you.
The key to the surge is not to just accomplish the shift, it's to minimize the loss of momentum that can create a gap between you and someone else (or create a gap). Obviously, my take on this comes from being a bike racer but as mentioned, front shifts on an incline require a pedal surge if you want them to go smoothly. This is especially true with a compact/sub compact cranks because the 16T difference between chainrings means a rear shift will probably have to happen as well.
A basic rule of thumb is "if it's making noise/not shifting for longer than a second, you're doing something wrong".