IMHO, our brake systems need to be vented or atmospheric changes may
cause brake problems.  I've seen what happens (occasional, and at the
time unexplained, dragging brakes that finally caused a pant fire after
an extensive taxi) when an aerobatic airplane was discovered to be
fitted with an un-vented plug on the reservoir (maybe to avoid fluid
seepage while inverted).  The some-time dragging brake problem never
recurred after changing to the standard vented plug at the reservoir.

John Chambers, Boise, Id
Leg2, 91% to go