Over the years of owning the 919, I've had different brake feels during different situations. I don't know what causes them.
When I did a track day at limerock park which is very hard on the brakes, I noticed my lever slowly required more and more pull to achieve the same amount of brake. The total amount of force required was the same, but the "bite" was less, assuming that means how much travel is needed from the initial contact of the pads to the rotors, to full stopping power. It doesn't return to the way it was before after cooling down. It takes maybe days before it's back to the way it was. This happens every time I really go hard on the brakes during a very spirited ride, like on the tail. And then some days, typically on colder and very humid days when the grass starts getting dew, my brake feels like a rock. Again, the same amount of pressure, only much less travel. I'm just curious to know what the science is behind this, as everywhere I look, people are talking about brake fade or hydraulic issues.