Storing bike with hydraulic brakes

[dave_sd]

Does anyone have any definitive proof that upside down storage of a bike with hydraulic disc brakes is harmful? I've done it for short times (changing flats on the trail), but never long term. My cousin hangs his bike upside down for storage without any ill effects, but he might not know any better.

[Jordan300]

I think if you have any air in your reservoir (which you shouldn't anyway) it'll cause problems when hung upside down.

[Bill]

(10-27-2010, 01:12 PM)dave_sd Wrote:  Does anyone have any definitive proof that upside down storage of a bike with hydraulic disc brakes is harmful? I've done it for short times (changing flats on the trail), but never long term. My cousin hangs his bike upside down for storage without any ill effects, but he might not know any better.

As strange as this might sound, if there is no leaks there should not be any problem.

[RobAR]

When disc systems first came to market in the 1990s, we had 'open' and 'closed' systems. 'Open' is like the brake fluid reservoir in your truck with air in it. This type is pretty much obsolete for bicycles these days, though a few still exist. Your truck was not designed to be upside down. With an Open system, air from the master cylinder can migrate over time, as bubbles, into the hose or even into the caliper piston. While this will not render the brake useless, it is not a pleasant experience. Feels "mushy". Early Magura's come to mind.
Todays 'closed' systems use bleeding procedures and tools designed to minimize any entrapped air.
With that said, I still do not recommend extended storage of ANY hydro-equipped bike upside down. Vertical storage, with levers (supposing that the master cyl is at the lever) upward should pose no problem.
As for the time spent fixing a flat? No sweat with either.