On mountain bikes with standard bar setups, the hydro tube generally always runs continuously uphill to the master piston and fluid reservoir. Bubbles can always migrate up and escape into the expansion reservoir. What if you had a loop of tubing extending up above the bar noticeably, and the reservoir was down lower, or the brake lever were even mounted vertically (lever down) as with a road bike or some recumbents? You'd be screwed, huh? I have seen hydro systems on recumbent trikes where they were mounted vertically, lever up so the res was the highest point. That makes sense, but I guess you couldn't flip this system over.
On a closed system (like the Magura HS33 hydro rim brake) all of this would be moot, I guess.
Mtbr's 2016 Winter Biking GearReviews and Roundups
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