What is a throwout bearing?

A throwout bearing, more commonly known as a clutch release bearing or hydraulic release bearing, is a key component in the clutch system, located between the clutch and the transmission. Its main function is to drive the clutch pressure plate away from the friction discs when the clutch pedal is depressed, thus interrupting the transmission of power between the engine and the transmission.

The throwout bearing is a crucial component in manual transmission vehicles, responsible for separating the power connection between the engine and transmission during gear shifts. The following is a detailed description of how it works:

 1. Definition and Location

The throwout bearing is located within the clutch assembly, immediately between the clutch pressure plate and the release fork. In some modern vehicles, it may be integrated into the hydraulic system as part of the hydraulic slave cylinder.

 2. Principle of operation - mechanical throwout bearing

- Power interruption activation: When the driver depresses the clutch pedal, force is transmitted to the release fork via a series of mechanical links or cables.

- Bearing activation: the movement of the release fork in turn pushes the throw-out bearing, which contacts the centre of the pressure plate either directly or via an intermediate mechanism.

- Separation: with the advance of the throw-out bearing, the pressure plate is pushed away, reducing the pressure on the clutch discs and allowing them to separate from the flywheel, thus interrupting the transmission of the engine speed to the wheels and creating the conditions for shifting gears.

 3. Principle of operation - hydraulic throwout bearing

- Hydraulic pressure transfer: In a hydraulic system, when the clutch pedal is depressed, pressure is generated in the master cylinder, which pushes hydraulic fluid into a hydraulic throwaway bearing (or integrated slave cylinder) located near the gearbox.

- Contactless disengagement: The hydraulic pressure moves the release bearing or piston forward and acts indirectly or directly on the pressure plate to disengage the clutch, again for the purpose of power interruption.

 4. Importance of the throw-out bearing

- Smooth Shift: Ensuring that the clutch can quickly and smoothly disengage and engage during each shift is the key to ensuring vehicle manoeuvrability.

- Protective Mechanism: Prevents shifting under power transmission and reduces mechanical damage.

- Feedback Sense: Provides the driver with a tactile sensation of the clutch pedal to help judge the clutch point.

 5. Maintenance and breakdown

- Wear and Noise: Due to the constant high friction environment, the throwout bearing is prone to wear and when worn it may produce noise when the clutch is depressed.

- Regular Inspection: Although not easy to maintain directly, regular inspection of the clutch system can prevent larger problems caused by a faulty throwout bearing.

 6. Design and materials

- Durable design: In order to cope with high temperatures and pressures, throwout bearings are usually made of high quality bearing materials and designed to ensure long term reliability and performance.

- Lubrication Requirements: Whilst some designs do not require direct lubrication, it is still important to keep the inside of the clutch system clean and properly ventilated.

7. Failure and maintenance:

Release bearings may fail during prolonged use due to wear, poor lubrication or external impact. Failed release bearings can cause problems such as difficult clutch operation, poor gear shifting or untimely interruption of power transmission. Therefore, regular inspection and maintenance of the release bearing is one of the most important measures to ensure the normal operation of the clutch system.

In summary, the throwout bearing is an indispensable component in a manual transmission vehicle, which ensures that the clutch can be effectively disengaged when required through precise mechanical or hydraulic action, thus enabling the driver to shift gears smoothly. Whether it is a mechanical direct contact or a hydraulic indirect action, its core function is to ensure the control and efficiency of power transmission and is an integral part of the vehicle's drivetrain.