Quote:
Originally Posted by Stu
A related question then. Bleeding brakes consists of getting air out of the calipers from the bleed nipple right? what if there is air in the lines? It would rise up to the master cylinder does it just escape naturally when you use the brake lever? 
(same as zip tying the brake lever on overnight) |
No it wouldn't because it's a sealed and pressurised system, the master cylinder is effectively a one way valve, fluid can go down through cylinder from the reservoir into the brake lines, but nothing can come back up, so the air bubble would definately stay where it was. Bubbles in a brake line can only go down, hence bleeding from the caliper.
I'm not sure even above the cylinder that air will rise and escape due to the viscosity of the fluid. Even with something as fluid as water you get small bubbles trapped in small spaces due to the viscosity and surface tension of the fluid being stonger than the bubbles bouyancy.