What is the purpose of the bleed screw in a hydraulic brake circuit?

Question

DentroTest · Accepted Answer

The essential job of the bleed screw (bleeder) is to allow the air bubbles trapped inside the hydraulic lines to escape. Brake fluids are incompressible, whereas air is highly compressible; if there is air in the circuit, the force applied to the pedal is lost compressing that gas, causing a spongy feel and a critical loss of braking force. The other options are incorrect: the maximum pressure of the system is regulated by specific safety valves (limiting or compensating valves), and filling or topping up the fluid is always done through the upper reserve reservoir, never through the bleed screws.

What is the purpose of the bleed screw in a hydraulic brake circuit?

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