prj71

I'm not sure why you are focused on speed. But when I'm riding (and this is probably the same for the majority of folks) there comes a point (usually a hill climb) where either the legs want to give out or the lungs want to give it out (or sometimes both) which is the physical indicator that a person should shift to an easier gear. Or if riding on the flats and the pedaling is too easy or the cadence is super high...it's another physical indicator to shift to a harder gear. This isn't that difficult and you don't need an indicator to tell you when do these things. Your body tells you. This is a no brainer common sense thing...well at least for some.

I was reminded last night on our group road ride, where we were rolling along at 25 mph for 8 miles, that having to look at a gear indicator or at your cassette for a split second could result in a crashy experience. Keep an eye on the bike in front of you and shift as needed according to what your body is telling you.