Originally Posted by BrokenVert
Coulthard always said it was a brake Bias lever down there when Schumi plays with it. I trust him with all things F1.
Both Coulthard and Brundle refer to it as Brake Bias. Whether Brundle just got it from Coulthard or knew from his own time as a driver back then is unknown. But it's safe to say it is bias with relative certainty.
I believe Schumacher himself has confirmed its a bias adjustment, and that he tends to adjust it more often than most drivers. Which may be why you see Rosberg working it more often as well, picking up something from Schumacher. Though, Rosberg's qualy 3 lap at Bahrain was ruined because he attempted to alter the bias right before the hairpin where everyone was locking their wheels at, he missed the apex and lost time. Which let Vettel get pole.