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What is a Car Clutch? How Does it Work?

Team AckodriveMar 29, 2024

Whether you're a new driver trying to understand the clutch in your manual transmission or a more experienced driver looking to improve your skills, clutches play an integral yet often misunderstood role in how cars operate. This guide will explain everything you need to know about car clutches in simple terms - from their basic function to signs that need repair. You can confidently drive any stick shift with a better understanding of this important but tricky car component.

What is a Car Clutch?

The clutch plays an essential role in the manual transmission of cars and other vehicles. Its key purpose is to smoothly connect and disconnect the engine's power from the transmission and wheels. This allows gear changes to occur without grinding or clashing between mismatched speeds.

Without a clutch, drivers would have to perfectly match the engine revs to the transmission speed when shifting gears - an almost impossible task while driving. So, the clutch provides latitude and cushioning between the engine and drivetrain.

When the clutch pedal is not pressed, its plates join together and spin at the same speed, allowing engine power to flow through to the wheels. But when you put your foot on the clutch, it breaks that connection, enabling smooth gear changes.

Once the new gear is selected, slowly lifting off the pedal engages the clutch plates again and synchronises engine power with wheel speed. This process repeats every time gears need to be shifted.

How a Clutch Works?

A clutch is made up of two main parts - the clutch disc and the pressure plate. The clutch disc, sometimes called the driven plate, is connected to the transmission input shaft. The pressure plate is bolted to the engine's flywheel. In between them is a clutch cover, which exerts pressure to keep them together.When the pedal is not pressed, springs in the pressure plate clamp the two plates together, allowing power from the engine to flow through to the transmission. When the clutch pedal is pressed, it activates a release bearing that pushes the pressure plate back, separating the clutch disc from the flywheel. This breaks the connection between engine and transmission, allowing the driver to change gears.

How Many Clutch Parts Are There?

Five main components make up a car's clutch system:

Cover Plate: This clutch housing mounts the whole assembly to the flywheel.
Driven Plate: The clutch disc that is sandwiched between the pressure plate and flywheel. It has friction material bonded to both sides.
Pressure Plate: Bolted to the flywheel, it clamps and unclamps the clutch disc through a diaphragm spring.
Diaphragm Springs: Apply pressure evenly across the surface of the pressure plate.
Release Bearing: Pushes against diaphragm springs to release the clamping force when the clutch pedal is depressed.

How to Use a Car Clutch?

Using the clutch smoothly is key for safe driving. Here are some tips:

The first golden rule is to press the clutch pedal when changing gears. This breaks the connection between the engine and transmission, allowing you to move the shifter freely between gears without grinding.

Make sure not to ride or rest your foot on the clutch during regular driving. Keeping it partially pressed in can cause extra wear. Allow it to release once you've selected a gear fully.

When taking off from a stop, slowly lift your foot off the pedal to feel where the clutch begins to grab - this is called the bite point. Smoothly easing through this spot prevents the car from suddenly lurching forward.

Remember to press the clutch when coming to a full stop, too, whether at a light or a stop sign. Leaving it engaged may cause your car to stall out at low speeds.

Using these clutch pedal driving techniques correctly will soon become second nature. With practice, you'll be able to smoothly accelerate, shift gears, and flow with traffic without ever needing to think about the mechanical ballet your feet are performing.

What is the function of a Clutch in a Car?

The main functions of a car clutch are:

1. Transmits Engine Power

When engaged, the clutch connects the engine to the transmission, allowing power from the engine to be transmitted to the wheels to propel the vehicle forward. The clutch plates join and rotate at matched speeds to transfer rotational force down the drivetrain.

2. Enables Gear Changes

The clutch allows the vehicle's engine to be disengaged from the transmission when the pedal is depressed. This breaks the connection between the engine and gears, enabling smooth gear changes without grinding or clashing noises.

3. Allows Smooth Stops/Starts

Depressing the clutch pedal separates the engine from the drivetrain, allowing the vehicle to come to smooth and controlled stops even with the gear still engaged. This prevents the engine from stalling at low speeds yet keeps the transmission ready to accelerate again after the clutch pedal is released.

4. Cushions Driveline from Torque Spikes

The clutch also cushioned the drivetrain by dampening out sudden power surges from the engine. It allows torque to be transmitted smoothly to the wheels as the engine RPM builds, preventing harsh engagements.

5. Enables Progressive Acceleration

As the clutch begins to grab, a small amount of slippage occurs between the plates. This brief transition progressively increases the transmission to engine speed, aligning wheel rotation for jerk-free acceleration before full lockup.

Lifespan of a Car Clutch

The typical lifespan of a clutch depends on driving style and conditions. On average:

60,000 - 100,000 miles for normal street usage
30,000 - 50,000 miles for performance/race usage
150,000+ miles for highway/city driving

Aggressive driving, hauling heavy loads, stop-and-go traffic, etc., can shorten clutch life considerably. Signs like clutch slippage indicate the clutch needs replacement. With proper driving habits, you can maximise clutch lifespan.

Common Clutch Problems

Some common clutch-related issues are:

a. Clutch Slippage

Over time, the clutch disc lining can become worn down from excessive use. This causes the clutch to lose grip and slip when accelerating or when hauling/towing heavy loads. The slippery plates fail to fully transfer the engine's power, leaving you lacking acceleration. This progressive clutch slippage will eventually render smooth driving impossible until the lining is replaced.

b. Clutch Drag

Oil contamination of the clutch components can cause things to become "sticky." This added friction makes pressing the clutch pedal and changing gears harder. Components like the pressure plate may also become warped over time and not release fully. This constant slight contact keeps the transmission partially engaged, resulting in difficult shifter movement or gear grind.

c. Clutch Chatter/Vibration

The springs around the pressure plate keep the clutch locked together. If any become uneven, damaged or weakened, they apply pressure inconsistently. This allows vibrations and excessive chatter upon clutch re-engagement. The pedal may shudder underfoot, leading up to smoother engagement points. Finding that sweet spot bite point for a buttery smooth takeoff becomes possible.

d. Clutch Squeal

When you depress the clutch, that horrible metal-on-metal squealing or screeching sound indicates lubrication issues. The release bearing is not getting enough grease, causing it to squeak audibly during operation. Addressing this cheap fix early on prevents unnecessary wear. But left alone, you'll have to replace the whole bearing assembly.

e. Leakage

Oily patches underneath the car or clutch fluid levels dropping inside could point to seal damage around clutch hydraulics and cylinders. This allows fluid to leak out, leading to insufficient line pressure for full pedal operation. Identifying external or internal leaks early and replacing worn seals prevents bigger problems and more costly repairs.

Tips to Increase the Life of Car Clutch

You can prolong your clutch lifespan by following these tips:

Don't ride the clutch pedal and completely depress it when changing gears. This prevents extra wear.
Come to a complete stop before shifting into first gear from neutral. Avoid shifting on the fly.
Maintain proper clutch pedal free play for a smooth engagement. Refer to the owner's manual.
Change gear oil per manufacturer service schedule, as contaminants can affect clutch operation.
Drive smoothly and avoid sudden acceleration, as even slightly worn clutches may slip under heavy loads.
Following the proper clutch usage guidelines and driving style will increase longevity substantially.

Conclusion

The clutch plays a crucial role in transferring power to the drivetrain in manual cars, allowing smooth takeoffs and gear shifts. Understanding parts like the pressure plate, clutch disc and release bearing that enable this operation goes a long way in using it properly. Learning the right clutch control, biting point, and driving habits also prevents premature wear - helping you enjoy that manual driving experience to the fullest.