Can storing bicycles upside-down damage hydraulic brakes? I usually store our bikes for the winter hanging upside down by the wheels from the rafters. I would assume that I can't do this with a hydraulic disc brake bike: am I correct?
From Shimano Service Instructions:


  When turning the bicycle upside down or on its side the brake system may have some air
  bubbles inside the reservoir tank which are still there when the reservoir tank cover is
  replaced, or which accumulate in various parts of the brake system when it is used for long
  periods. The M755 disc brake system is not designed to be turned upside down. If the bicycle
  is turned upside down or on its side, the air bubbles inside the reservoir tank may move in the
  direction of the calipers. If the bicycle is ridden in this condition, there is the danger that the
  brakes may not operate and a serious accident could occur.
  
  If the bicycle has been turned upside down or on its side, be sure to operate the brake lever a
  few times to check that the brakes operate normally before riding the bicycle. If the brakes do
  not operate normally, adjust them by the following procedure.
  
  &lt; If brake operation is sluggish when the lever is depressed >
  Gently depress the brake lever several times and wait for the bubbles to return to the
  reservoir tank. It is recommended that you then remove the reservoir tank cover and fill
  the reservoir tank with brake fluid until no bubbles remain.
  If the brakes still operate sluggishly, bleed the air from the brake system.
  (Refer to "Adding the brake fluid and bleeding air".)