Originally Posted by
Amt0571
If that was true, nobody would be bleeding brakes because no air would get inside. If air is getting inside, that air has some degree of humidity, and that water has to go somewhere.
If you shorten the tubing you will get air in, or if you damage your seals. Mineral oil (unlike Dot oils) does not absorb moisture.
I do have two different bleed kits. But that's because I installed two sets of different brakes on two different bikes and the tubing had to be shortened. There is a huge difference between Dot oil brakes and mineral oil brakes.
I've had air bubbles appear from nowhere on Magura HS11 hydraulic rim brakes which are much simpler as they have no reservoir and are basically the equivalent of a couple of syringes connected by a spring. So it's not surprising air ends up getting inside much more complex hydraulic disc brakes.
Then you had a leak. Having a reservoir is not "more complex" than not having a reservoir.
Unlike most Magura brakes, the HS11 uses mineral oil. And mineral oil does not absorb moisture from the air or otherwise.
In any case It's really strange for a bicycle disc brake to accumulate enough water to pose a serious risk even if you don't change the fluid, but I've seen it happen once. My friend who was riding the bike was not happy.
Again: Mineral oil does not absorb moisture. Dot oils do (except the Dot 5 which is silicone). There is no "accumulation of water" with mineral oil brakes.
Replacing the fluid from time to time is cheap and better than crashing your head into a tree, so in my opinion it's worth it.
Completely unnecessary on mineral oil brakes.