Old 10-07-13, 11:48 AM
Dan Burkhart 
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Originally Posted by dabac View Post
The key difference between bike hydraulics and car hydraulics is "open" vs "closed" system. A car system is open, meaning the reservoir isn't under pressure and that the main cylinder will be refilled from the reservoir when the lever is released.
A bike system is closed, meaning there really isn't a reservoir to draw from. The system is blocked off at both ends, all the time.
If you think of bleeding a bike brake as first adding a reservoir, then the rest is pretty much like bleeding a car brake.
Some recommend that you should create some suction as well, to make it easier for any air bubbles to escape. The argument being that with the small volumes used in a bike, flow enough won't get rid of the bubbles as it does in a car.
Bleed kits do make the job easier and less messy, but if you look at the instructions you'll soon notice that the main part of the bleed kits are the syringes. And syringes you can get elsewhere, for less money. I've gotten mine from pharmacies and lab equipment suppliers.
With a bit of luck, you can jam them into the bleed ports well enough to get the job done w/o any further equipment.
There are open systems in the bicycle world too. Shimano would be the most obvious and common example.
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