Home Transmission & Drivetrain Flywheel Car: Functions, Types, And All You Should Know

Flywheel Car: Functions, Types, And All You Should Know

by Kelvin Yates

The generation of power in a vehicle is heavily attached to the vehicle’s powertrain, the engine, and transmission. But somewhere at the end of the engine is the car flywheel, often overlooked and underestimated, yet it has one of the most vital roles in powering a car.

A car flywheel is a link between the transmission of a car and the clutch in the vehicle. It determines the smooth change in gears and gives the power to accelerate at a softer pace when a vehicle is slowed and attached to the engine’s crankshaft to offset any imbalance from the engine’s weight. The flywheel is very important; damage to the flywheel results in various faults in the car, from a noisy clutch and sounds to the car not igniting.

A bad flywheel can wreak severe damage on your vehicle which will cost more to repair and trust me, you wouldn’t want to ignore your flywheel till it is badly faulty. This neglect can get you stranded, and your car might end up not starting at all.  You will get to know all you can from this article about the flywheel, how it works, and how to recognize when your flywheel is going bad.

What Is A Flywheel

The flywheel is an integral part of a vehicle, and it looks like a large, heavy round disc. It connects to the car’s crankshaft and moves with the clutch disc to push momentum to the car wheels. The flywheel plays a massive role in power delivery from the engine.

It is simply an energy storing device that conserves rotational energy to engine power for smooth delivery when attached to the rear end of a crankshaft. Flywheels can only be found in manual transmission cars and not automatic vehicles; instead, automatic cars use flexplates to connect the engine and transmission.

In manual cars, a flywheel aids in the proper functionality of the gears while the clutch is applied and reduces vibrations in the vehicle by balancing out the car’s engine. Attached at the back of a vehicle engine between the engine and the transmission, it offers extra friction for the clutch and uses its teeth to engage the starter.

So when you turn the car keys, the flywheel gets rotated by the starter motor, which spins the crankshaft and causes the engine to start. Your car needs to have a proper functioning flywheel for clutch engagement and gear change. Without a flywheel, your car will not move when you clutch at a standstill position due to no momentum that the flywheel offers.

Car Flywheel

Car Flywheel

A flywheel plays a lot of functions in a car, it is necessary to understand the functions of a flywheel; this will help you see the importance it plays in a vehicle. Flywheels are present in cars, trains, and even buses. flywheels serve the following functions in a car:

1. Engine Starting

When the key is inserted and turned, the gear teeth cut into the flywheel’s flat surface, transmitting power to the engine. The motor gears grind up in the machine and spin with the flywheel. It rotates the flywheel, and in turn, the crankshaft turns and starts the process necessary for the engine to start correctly. The motor gear releases once the engine starts, and the flywheel continues.

2. Smoothing Engine Speed

To maintain the smoothness of speed, the flywheel’s mass applies inertia to help the crankshaft turn between the pistons firing; this way, the rotation of speed is maintained, and the engine goes smoothly.

3. Engine Balancing

The engine will vibrate as the pistons fire because of the pistons at the center of the crankshaft. For a more balanced weight, the flywheel attaches to the crankshaft and stabilizes the side to side wobbling of the engine. This attachment helps to reduce the rate of vibration of the car.

4. Drivetrain Stress Reduction

The flywheel reduces the stress exerted on the car’s drivetrain by stabilizing the movement of the engine; This stabilization reduces wear and tear to the rest of the drivetrain. The driveshaft uses universal joints while working, and these joints constantly change angles. The flywheel helps reduce frictional wear on these types of joints.

5. Weight Manipulation

The heaviness of a flywheel determines the specific performance of an engine. Very heavy flywheels permit the machine to work with loads that may have weighed down the engine. Heavy flywheels are in trucks and heavy trailers, and the weight of a flywheel can be manipulated to the use and specifications of a car, just like light flywheels are in race cars.

Two Types Of Car Flywheel

Although there are different sizes, models, and makes of flywheels, there are two significant types of flywheels: the lightened flywheels and the dual mass flywheel.

1. Lightened Flywheels

These are usually in race cars and performance cars; like the name, they have a significantly reduced weight and are very light. Reducing the excess material from a flywheel to fit a specific one gives the flywheel more rotation speed under the engine’s power. It makes it more accessible to change gears to suit the rate necessary. This speed makes the lightened flywheels ideal for race cars.

2. Dual Mass Flywheels

This type, unlike the lightened one, has a weighty mass, hence the double in its name. For heavy-duty vehicles, the weight of the flywheel is to balance off the engine’s load and help keep balance. These flywheels do not have much speed in rotation, and swift gear changes are not entirely possible.

Flywheel Resurfacing Near Me

It is essential that the flywheel is always in top-notch condition, and to ensure this, you can resurface a flywheel whenever a clutch is changed, or when it indicates early signs of damage. Flywheel resurfacing is the process of shaving or grinding off cracks and damages on the flat surface of a flywheel.

Heat and friction generate a lot when the clutch is applied; this affects the flywheel’s mass because it absorbs and expends the heat. As the clutch starts getting faulty or slips, more heat produces, and there is additional heat stress on the flywheel.

This heat causes heat cracks, hard spot formations, and warpage on the flywheel surface. The flywheel has to be resurfaced and the clutch replaced. A recommendation is that the flywheel is scrutinized and resurfaced during a clutch replacement if there is any defect. This inspection includes measuring the flatness and inspecting for cracks, hard spots, and grooving.

Replacement of a clutch without resurfacing a defective flywheel will only spoil the clutch; it is a waste of money and might lead to other damages. If the cracks on the flywheel are too deep for resurfacing, please replace the flywheel.

Ways Resurfacing Can Be Done

Resurfacing can be done in two different techniques.

  • Cutting: The brake lathe can be cut and set up on a lathe, this method takes time, and one must be very careful to ensure the flywheel turns correctly on the lathe. Cutting also has the disadvantage of skipping hard spots and leaving unevenness on the flat surface.
  • Grinding: This technique is usually done on a block grinding machine or a flywheel grinder. With the flywheel grinder, the defects will be shaved off to get a flat even shape wheel.

It is important to remember that any defect can stall the clutch in flywheel resurfacing. Change the flywheel if resurfacing won’t do the trick, and use professionals for the work.

Flywheel Resurfacing Cost

The cost of resurfacing a damaged flywheel is always worth the future stress it could cause. The replacement price varies and is always higher than resurfacing the flywheel. A flywheel can be resurfaced for an average of $50 to $100 and can take a few hours of labor to get it all done.

Dual flywheels cannot be resurfaced and will need to be replaced; replacing a dual flywheel is at an average of $200 to $1000.

Flexplate Vs Flywheel

Flex plate and flywheel are always mistaken to be the same; though they have similarities and may serve the same purposes, they are not the same. There are a bunch of differences between a flexplate and a flywheel. Like;

  • Transmission: Flexplate can be found in automatic transmission vehicles, while the flywheel is in manual transmission vehicles.
  • Appearance: The flexplate is much thinner and lighter than the flywheel; this is because a flexplate should flex across the central axis while rotation speed changes, but the flywheel is thick and heavy and has a large smooth flat surface.
  • Location in the Car: Though both the flexplate and flywheel connect to the transmission, they converge at a different points. The fly plate fixes the crankshaft and the torque converter, while the flywheel is to the crankshaft and the clutch pedal.
  • Type of Bolts: Using flexplate and flywheel bolts interchangeable is impossible. The flexplate bolt is longer and has a flange head, while the bolts for the flywheel are shooter and always star-shaped.

Bad Flywheel Symptoms

Faults in a flywheel can result in several deficiencies in the smooth running of a car. To determine if your car has a bad flywheel, look out for some or all of these symptoms.

  • Gear Slip: Gear slipping occurs when there is no power being transferred to the wheels and is always a result of the worn-out clutch. Wearing out the clutch will affect the flywheel to wear out too, and eventually, the flywheel will crack, making gear change impossible. When you start experiencing gear slipping, check out your flywheel and fix the clutch to avoid more damage.
  • Acrid Burning Smell: You may perceive an acrid burning smell inside the vehicle; that is a sign that your flywheel is terrible. The odor comes from improper clutch handling, wearing out the flywheel. Clutches have facings to reduce noise; they can also overheat due to friction when misused and produce a burning odor.
  • Clattering of the Clutch: When the clutch skips on the flywheel and gives a vibration feel when you release, that’s a sign the flywheel is bad.
  • Vibrating Clutch Pedal: Vibrations from the clutch pedal can also mean that the spring mounts on the flywheel are bad.
  • Dragging of Clutch: When you experience the clutch not engaging, or a complete failure to put the vehicle in first gear, you might be having a clutch drag due to failure of the flywheel.
  • Car Not Starting: Though a car not starting can be due to several other reasons, it can also be because of a faulty flywheel. If the clutch and the flywheel don’t engage properly, the car might not start.

Though most of these symptoms might be because of other reasons, they can also indicate a fault in the flywheel.

Flywheel Replacement Cost

Flywheel replacement is necessary when the flywheel is damaged beyond resurfacing; it is worth spending the amount you will for a long-lasting vehicle. Driving a car with a bad flywheel is a NO-NO; the car is an accident beacon. However, if the car is a very old one, the money spent might not be worth it; consider getting rid of it.

Replacing a flywheel is not the cheapest expense in a car; it is labor-intensive; therefore, labor is the main charge and can go as high as $90 to $150 per hour; Labor costs can be around $500 in all. This cost is due to difficulty detaching the flywheel and replacing it to sync with the other mechanism.

The flywheel itself has varying prices according to the make and model of the car; it can range from $50 to $500. Please do not replace the flywheel yourself if you don’t have prior mechanical experience. Contact a professional to do it, it is a highly complex process, and many things can go wrong.

What Is The Physics Behind A Car Flywheel?

Flywheels have kinetic energy, generating energy from motion by rotation. This energy is obtained from the moment of inertia and the angular velocity. I will explain it better, the moment of inertia is obtained from how much material the flywheel is made of and how fast it rotates.

The formula for the kinetic energy in a flywheel is;


the I is the moment of inertia.

The ω is the angular velocity.

Yes, these are very confusing and not easy to grasp, but it’s better to understand them with this; in a flywheel, the weight of the rotating object depends on where the mass is located and the spinning around point. The farther the center of the mass from the spinning point, the more influence the mass has on the object’s kinetic energy.

Therefore, a flywheel with a larger diameter and lightweight will have a much higher moment of inertia than a small, heavyweight flywheel. This moment of inertia is because the mass is further from the rotation point. The physics behind the flywheel is not necessary to random car users, but it’s cool to understand it works.

Flywheel Facts: What They Are and Why They’re Important

  1. A flywheel is a heavy disc attached to the end of a rotating shaft that helps smooth out the engine’s power pulses and store energy through rotational momentum.
  2. In automotive uses, the flywheel is usually a solid, metal disc that’s about an inch thick, a foot in diameter and around 10 to 40 pounds.
  3. Without a flywheel to smooth things out, the crankshaft would slow down during the compression stroke; then accelerate rapidly during the power stroke, coast through exhaust and intake strokes; then repeat the process. This would result in an uneven flow of power and a decent amount of vibration.
  4. The flywheel helps provide a more consistent speed and keeps the shaft turning even after you let go of the handle.
  5. In automotive uses, the flywheel also has another purpose as the starter motor pushes a gear in mesh with teeth at the outer rim of the flywheel to turn over the engine.
  6. The flywheel in a vehicle with a manual transmission provides a smooth, flat friction surface that helps grab the clutch plate when you release the clutch pedal.
  7. The word “flywheel” is sometimes a misnomer nowadays in the automotive world, and on vehicles with an automatic transmission, that part is often referred to as a flexplate.
  8. A flexplate is usually thinner and often has holes in it, making it significantly lighter than a flywheel.
  9. The flexplate still performs the functions of smoothing out the power flow through rotational momentum and providing an outer ring of teeth for the starter motor to engage.
  10. Nearly all automotive engines of recent years — and for most of the last century — have a four-stroke design, with each “stroke” being 180 degrees or one-half turn of the crankshaft.

Frequently Asked Questions About Car Flywheel

Here are some popular FAQs:

What Is A Flywheel On A Car

A flywheel on a car is a round disc-like heavy metal attached to the transmission of a manual transmission car that conserves energy and disburses conserved energy for momentum or smoothness in combustion and compression of the car pistons.

What Does A Flywheel Do

A flywheel serves as a connection that transfers and interrupts power between the engine and the transmission. It uses the clutch as the mode for connectivity. It also helps keep the engine’s balance and offers mass for rotational inertia. A flywheel is a means to start the car engine(with the energy it conserves).

How Does A Flywheel Work

A flywheel generates and stores energy by spinning at high speed, or “high moment of inertia” the more acceleration the flywheel spins, the higher the energy it holds. Flywheels store power as kinetic energy and this energy is utilized in a car to start the engine or smooth out acceleration when the vehicle is slowing.

Where Is The Flywheel Located

The flywheel is at the tail end of the engine. It is between the crankshaft and the clutch and is directly in the power transmission path. It balances the engine’s weight and transfers or cuts off power to the engine.

Do Automatic Cars Have A Flywheel

Automatic cars do not have a flywheel; a flywheel is in cars with a manual transmission. Instead, automatic cars use flexplates to perform the same duties as the flywheel. The flexplate is thinner and has less weight than the flywheel.

How Many Flywheel In A Car

There is always one flywheel in your car which is attached to the crankshaft at the engine’s end. Exceptions can be in unique customized cars with two or more engines installed, which can switch from one to the other. In this case, they will be a flywheel to every engine available.

How To Start A Car With A Bad Flywheel

Starting a car with a faulty flywheel depends on the level of damage to the flywheel. You can keep turning the key till the flywheel teeth connect and the engine starts, then drive slowly and carefully, avoiding sudden stops and clenching of gears. Driving a car with a faulty flywheel is very bad and can cause an accident or stranding.

How Much Is A Flywheel For A Car

Flywheel prices can range from $50 to over $500. It varies with model and car make. If the flywheel is an OEM replacement, it’ll cost more or aftermarket. No matter the price, it is necessary to replace it when it is faulty.

What Does A Bad Flywheel Look Like

A damaged flywheel will look brownish and have splitters and cracks on the flat surface. It can also have swollen-like spots around the exterior and burnt marks from overheating. They may be smears of metal and pieces of metals missing in extreme cases.

Can A Bad Flywheel Cause Starting Problems

Yes, a lousy flywheel will cause problems ranging from gear slip, clutch pedal vibrating, burning odor, vibrations from engine imbalance, to the car not starting at all. Flywheel is one of the items you want to check regularly because a fault on it means your car may be unable to start till replacement.

Does The Car Flywheel Need To Be Replaced With A Clutch

Most times, the flywheel is always replaced or at least resurfaced while changing the clutch, though it is not always necessary, especially when the flywheel is still in good condition. You can change the clutch alone; However, if the clutch change is for a car with lots of mileage, you should change both.

How Do I Know When My Car Flywheel Has Come Loose

When a flywheel loosens, your car will not ignite when the ignition turns. Whenever a car turns on, you will hear a clicking or grinding noise; the absence of this noise means that your flywheel has come loose. Have a professional inspect and repair your vehicle as soon as possible.

Is A Flywheel Supposed To Spin Freely

The flywheel on a car engine is supposed to be free-spinning. That’s because it’s part of the engine’s timing system, and it needs to rotate freely in order for the engine to start. The flywheel also provides some resistance when you’re trying to start your car, making it easier to crank the engine over.

What Would Cause A Car Flywheel To Spin Freely

Free-spinning happens when there is no contact whatsoever with the starter gear. Free-spinning can occur due to a motor malfunction of the starter gear. When you experience this, it is better to find a good mechanic or technician to handle it.

Can I Replace My Car Flywheel Myself

You can replace the vehicle flywheel yourself if you’re accustomed to the internal workings of the car or have prior professionalism on how to fix a flywheel. Alternatively, contact a good service point to service your car when it develops a flywheel fault.

Conclusion On Car Flywheel

The flywheel plays one of the most crucial roles in a car; therefore, it must be maintained and replaced when faulty. This article has exhausted everything about the flywheel, but we recommend you reach out to a professional care service when your flywheel gives you false symptoms.

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