On brakes?
To prevent pad knockback. This is when the hub flexes sufficiently to move a rotor and actually move the brake pads back into the caliper when you're off the brakes. My Stoptechs did this. Apparently it's a pretty common occurrance in road racing, but it's a little disconcerting to me. An old road racing trick (i've heard) is to just barely stab the brake before a corner (and your braking zone) to get the pad to contact the rotor again. Then when you go into the corner you dont have 3 inches of pedal slop before contact.