Car Engine Flywheel: Functions and How It Works

  • Function
  • Types
  • Components
  • Maintenance
  • FAQs

The flywheel is a silent hero in your car’s engine, ensuring everything stays in balance. It is one of the crucial components working behind the scenes to guarantee smooth operation and overall engine performance. Let’s discuss more about the functions of a car engine flywheel, its importance in a car engine and the mechanics behind its operation.

What is a Car Engine Flywheel

A flywheel is a mechanical device that stores rotational energy in a vehicle’s engine. It is typically a large, heavy wheel mounted on the engine’s crankshaft. The flywheel is usually located at the rear of the engine and close to the transmission. The flywheel is integral to the engine’s functionality and contributes significantly to its efficiency.

Functions of a Car Engine Flywheel

A car engine flywheel
The flywheel plays a critical role in starting the engine.

Before we dive into how flywheels work in cars, let’s understand their functions. Flywheels are found in almost all types of vehicles such as race cars, trains and buses. Previously, they were big wheels with spokes and a heavy metal edge. Nowadays, they’re smaller and made from materials like composite or carbon fibre. Let’s explore the functions of a car engine flywheel.

Engine Start

You can find different types of engine layouts available in vehicles. In a car, the flywheel plays a critical role in starting the engine. In manual transmission cars, the starter motor engages with the toothed ring on the flywheel’s outer edge. The motor turns the crankshaft and initiates the compression cycle needed to start the engine. Once the engine starts, the starter motor disengages, allowing the flywheel to spin freely.

Engine Speed Smoothing

After the engine starts, the crankshaft converts the piston’s up-and-down movement into rotary motion. This conversion can result in a somewhat jerky motion. The mass of the flywheel provides inertness, smoothing out the rotation speed of the crankshaft and ensuring a consistent and smooth engine operation.

Engine Balancing

The offset positioning of pistons from the centre of the crankshaft can lead to engine vibration and wobbling. The flywheel’s substantial weight counteracts this side-to-side motion, contributing to the stabilisation and balance of the engine on its mounts. This, in turn, helps reduce overall vibrations throughout the vehicle. 

Drivetrain Stress Reduction

By stabilising the engine’s movement and ensuring a smooth rotation speed, the car engine flywheel plays a role in limiting wear and tear on other drivetrain components. This is particularly crucial in maintaining the longevity of universal joints in the driveshaft, which constantly change angles during rotation. However, if the U-joint on a driveshaft stops working, it’s a sign of a bad driveshaft.

Weight Manipulation for Performance

Custom engine builders often adjust the weight of the flywheel to tailor an engine’s performance for specific purposes. Heavier flywheels are advantageous in situations where the engine may bog down under heavy loads, such as when consistently pulling trailers. On the other hand, lighter flywheels benefit high-speed engines, like those in race cars, by improving acceleration.

Types of Flywheel Car Engine

 rimmed flywheel is made of strong steel and has a rim
Car engine flywheels come in various types

Flywheels come in various types, each tailored for specific applications.

Solid Disc Flywheel

A solid disc flywheel is a robust component commonly used in single flywheel threshers. Comprising a hub and disc, its design calculations incorporate various parameters, including dimensions, to ensure optimal functionality.

Rimmed Flywheel

A rimmed flywheel is made of strong steel and has a rim that explodes at lower speeds than a solid disc flywheel. Its tapered disc design makes it lighter while storing a lot of energy.

High-Velocity Flywheel

High-velocity flywheels operate within a remarkable speed range of 30,000 to 80,000 rpm, with the flexibility to be adjusted up to 100,000 rpm. These flywheels utilise magnetic levitation bearings, requiring minimal maintenance. Despite being lighter than their low-velocity counterparts, they tend to be more expensive.

Low-Velocity Flywheel

Low-velocity flywheels spin at 10,000 rpm and are heavier than high-velocity ones. They need regular maintenance, don’t have magnetic levitation bearings, and might need special concrete for installation. Despite this, they are a more budget-friendly option.

Components in Flywheel

Flywheels are typically constructed from robust materials
A dual-mass flywheel design helps in enhancing the vehicle’s performance

A car engine has several parts and a flywheel is one of them. A flywheel in a car engine is a relatively simple mechanical component, but it involves several important parts that contribute to its functionality. Here are the key components of a flywheel:


Flywheels are typically constructed from robust materials such as cast iron or steel due to their high density and durability. Performance or lightweight vehicles may use materials such as aluminium or composite alloys. Here is more about commonly used automotive materials and their history.

Dual-Mass Flywheels

In some modern vehicles, a dual-mass flywheel design is employed to further enhance performance. This design features two masses connected by a damping mechanism, which reduces vibrations and enhances the overall driving experience.

Ring Gear

The ring gear is mounted on the outer perimeter of the flywheel. It plays a crucial role in the starting process. It engages with the starter motor’s pinion gear, facilitating the rotation of the flywheel and subsequently the engine. However, due to a failed starter motor, your car can take longer to start.

Friction Surface (for manual transmissions)

It is a specific area on the flywheel where the clutch engages. In manual transmissions, the pressure plate and clutch disc make contact with this surface. Since slipping the gears can damage the clutch and cause other issues, make sure you always check if there are any other signs of a bad car clutch.

Besides, you can consider exploring these  SUVs with manual transmissions for your upcoming purchase.

Flex Plate (for automatic transmissions)

It is similar to a flywheel but used in automatic transmissions. The flex plate helps in connecting the torque of the transmission.

How Does a Car Flywheel Work

Let’s find out how the car engine flywheel works when you start the engine.

Power Strokes

During the power strokes of the engine, energy generated by the combustion process is transferred to the flywheel through the crankshaft. This energy is stored in the rotational motion of the flywheel. 

Kinetic Energy Preservation

A flywheel operates similarly to a mechanical battery, preserving energy in the form of kinetic energy or movement. The amount of energy a flywheel can store is directly proportional to the square of its rotational speed. This means that the faster the flywheel spins, the more energy it can store.

Power Release

During non-power strokes, when the engine is not actively generating power, the flywheel releases the stored energy. This prevents the engine from slowing down excessively between power strokes, maintaining a smooth and controlled operation.

Starter Motor Engagement

During engine start-up, the starter motor engages with the ring gear on the flywheel. This engagement enables the starter motor to turn the flywheel, initiating the engine’s operation. 

Maintenance and Troubleshooting

The main job of flywheel is to store energy
Keep a car flywheel lubricated and check for any signs of wear

Maintenance and troubleshooting of the flywheel are vital to ensure the proper functioning and longevity of the engine. Here are key steps for keeping the flywheel in good condition:

Regular Inspection and Lubrication

  • Wear, Cracks and Imbalance: Periodically inspect the flywheel for any signs of wear, cracks or imbalance. Look for visible damage or irregularities on the surface.
  • Ring Gear Teeth: Ensure that the teeth on the ring gear, especially in manual transmissions, are in good condition. Damaged teeth can affect the engagement with the starter motor and your car won’t go into the correct gear.
  • Lubrication: Properly lubricate the flywheel’s mounting components to reduce friction and prevent premature wear. Lubrication is essential for the smooth operation of the flywheel.

Replacement and Balancing

  • Significant Wear or Damage: If you witness the signs of a bad flywheel, consider replacing it. Signs of wear may include grooves, warping, or visible damage.
  • Proper Balancing: During replacement, ensure that the new flywheel is properly balanced. Balancing is critical for reducing vibrations and maintaining the overall performance of the engine.
  • Professional Balancing Services: Seek the expertise of professional balancing services to achieve the desired balance. These services use specialised equipment to ensure precise balancing, contributing to smoother engine operation.


What is the purpose of a car flywheel?

The main job of flywheel is to store energy and keep the engine running smoothly. It takes the energy created when the engine is running and helps balance things out, so your engine performs well.

Why is it called a flywheel of a car?

The term flywheel comes from combining ‘fly’ and ‘wheel,’ essentially meaning a wheel that rotates fast. In the context of a motor, the flywheel is the primary wheel that rotates and transfers energy to other belts. It used to be the central motor that powered various components in a mechanical system.

Where is the flywheel located in a car?

The flywheel is typically located at the rear end of the engine, bolted to the crankshaft. In a manual transmission setup, it is positioned between the engine and the clutch assembly. In an automatic transmission, a similar but slightly different component called a flexplate is used in place of the flywheel.

This is all about the flywheel, its types and functions. It stores energy, helps with smooth power delivery and keeps the engine running well. To make sure your car stays in top shape, it’s important to check the flywheel regularly, give it proper care and follow the car maker’s advice. 

Hence, when searching for used cars for sale in the UAE, ensure that the vehicle boasts a well-maintained flywheel and other essential components to steer clear of any potential issues.

Stay connected to dubizzle car blogs for further insights into car parts and their functionalities.


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