What is a dual mass flywheel (DMF)?

Dual mass flywheels are fitted to many diesel and some petrol vehicles. They eliminate excessive transmission noise, protect the gearbox from damage, reduce gear change effort, and increase fuel economy (as the engine works at a lower rpm). The DMF acts as a damper between the crankshaft and the input shaft on the gearbox. They are made of two parts connected to a central friction ring that allows slip between them and work by having a set of springs inserted between two rotating masses; the slip is cushioned by a set of springs that smooth out irregular torque pulses from the engine. The springs are sized to absorb some of the vibration from the engine under load conditions.

These irregular forces can cause excessive transmission noise, difficult gear change operations and increased wear to the drive train components. All DMFs wear out over time and we recommend that if the clutch is being replaced, the DMF should also be replaced.

What is a clutch kit?

A clutch kit is a group of components related to the clutch.

A clutch kit has at least two components; a clutch disc and a pressure plate which is known as a 2 piece clutch kit. A 3 piece clutch kit has 3 components; a clutch disc, a pressure plate and releaser. A 4 piece clutch kit has 4 components; a flywheel, clutch disc, a pressure plate and releaser.

The clutch kit components are;

  1. The flywheel
    The flywheel (either solid or dual mass) is connected directly to the engine crankshaft and, therefore, spins with the engine’s motions.
  2. The pressure plate
    Bolted to the flywheel is the clutch pressure plate. The spring-loaded pressure plate has two jobs: to hold the clutch assembly together and to release tension that allows the assembly to rotate freely.
  3. The clutch disc
    Between the flywheel and the pressure plate is the clutch disc. The clutch disc has friction surfaces similar to a brake pad on both sides that make or break contact with the metal flywheel and pressure plate surfaces, allowing for smooth engagement and disengagement.
  4. The release bearing and/or release system
    These components work together simultaneously and are key to the engaging and disengaging process in conjunction with the slave cylinder.

The clutch release bearing is connected to one end of the hydraulic (or clutch fork mechanism) and moves on the diaphragm spring of the clutch. Depending on the type of release system, the bearing either pulls or pushes on the pressure plate diaphragm spring to engage or disengage the pressure plate's grip on the clutch disc when the clutch pedal is depressed and released. Some vehicles may also use a concentric slave cylinder which combined the operation of the conventional slave cylinder and the release bearing in a single unit.

Why is it a good idea to use a DMF?

Modern engine technology places higher and higher demands on clutch systems and drive train. Engines are optimised for fuel consumption and will have high torques with low speeds. The usable engine speed range is additionally reduced towards the idling speed level to enable fuel-efficient and low-emission driving. This increases the combustion engine's rotational irregularities. For the driveline and driver, this means increased vibrations, increased noise, and reduced comfort. This is where the DMF comes in as a powerful vibration isolator. It helps protect the driveline against harmful vibration and ensures low-noise and comfortable driving.

What are the symptoms of a failing DMF?

Diagnosing a failing dual mass flywheel can be tricky since most of the symptoms can also mean issues with the clutch itself. If you suspect your dual mass flywheel needs replacement we would again recommend you to contact your local mechanic or gearbox specialist (we can recommend some in your area) and arrange them to take a look at it. A definitive assessment will involve visual inspection of all components, but if you have any of these issues, then your DMF could be the issue;

1. Noise. If you hear a lot of rattle or banging sounds from the gearbox bellhousing, most likely the DMF has failed. These noises can be very loud and it should be replaced as a soon as possible.

2. Slipping. When a clutch is slipping due to wear or otherwise not being up to capacity to the demand placed on it, you get a burning smell like that of burnt bread and gear oil mixed together. This usually happens first in the higher gears due to the higher gear ratios and increased wind resistance. If you do NOT smell the facings burning up when this is happening, it is your dual mass flywheel that is slipping and it needs to be replaced.

3. Vibrations. These vibrations can usually be felt on the floor of the car and are due to the failure of the springs and other internal components. This leads directly to the flywheel’s inability to dampen the tremors with use and it must be replaced.

Failing DMF

What are the options when replacing the DMF?

The replacement of a worn DMF with another DMF is an obvious option. However, the cost of this option is sometimes prohibitive. For some vehicles, single mass flywheel (SMF) conversion kits are available which are sold together with the pressure plate, disc and release bearing or concentric slave cylinder (CSC) to replace the DMF system. The main advantage of an SMF kit is the price – they are generally cheaper to purchase.

replacing dmf

What is a single mass (solid) flywheel (SMF)?

A single mass (or solid) flywheel provides a direct contact between the engine and clutch assembly. They tend to be much cheaper than a dual mass flywheel to replace, and because they are made of one piece they can also be resurfaced if within factory specifications. Some vehicles come from the factory with solid flywheels (generally smaller petrol and diesel cars with low horse power).

While the SMF system is a popular choice for some vehicles, it’s important to note that despite the durability and price advantages, the SMF kits do not possess the same dampening characteristics as a DMF and may not sound or feel like the DMF system that is being replaced with increased engine noise, harsher gear changes etc.. Some clutch pressure plates contain springs to help dampen vibrations, but in general, an SMF cannot dampen engine vibration as well as a DMF.

How do I know if my car has a solid or dual mass flywheel?

If you are unsure as to whether or not your car has a solid flywheel from the factory, Contact Us with your car's registration number.

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Does a solid flywheel need to be replaced when changing the clutch?

In most cases, unless some damage has been done to the solid flywheel, it should not need replacing or resurfacing. We do not supply solid flywheels for cars which were originally fitted with solid flywheels from the factory, we only stock solid conversion kits which converts the dual mass flywheel to a solid flywheel.

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What is your warranty policy?

All parts carry at least a 12 month warranty.

12 months warranty

What is your returns policy?

To make a return, please contact us on 046 901 0136 to obtain a Returns Authorisation Number and we will guide you through the process.

Please note: A re-stocking charge applies to all returns of unused parts of up to 15% of the full invoice price including Vat on any part which is subject to a minimum value of €20.00 including Vat. The re-stocking charge will be at the discretion of Express Spares based on the source of the parts; e.g. if item was a special order.


Are your clutch and flywheels good quality?

90-95% of our stock is manufactured by LUK, Sachs or Valeo who are the largest manufacturers of clutch and flywheel components in the world. The quality of the components we sell are the same quality as the components which were fitted to the vehicle when it first left the factory, often 100,000 miles (or hopefully more) ago.


What about these fake clutches and flywheels doing the rounds?

We've yet to encounter any fake clutches or flywheels. 

Some large manufacturers source clutch and related components from other original equipment manufacturers (OEMs) and place it in their branded box to re-sell with their part number or branding on it.

Some OEMs have factories in different parts of the world which may use different stamps or branding which to some can look like imitation. 

You can rest assured that none of the parts we sell are replicas, imitations or fakes. 


How do I pay?

The majority of our sales are carried out over the phone and paid for via credit or debit card. You can also order certain components online on our website. You can opt to pay via cash or via credit or debit card in person at our warehouse.

How do i pay

Can I collect from your warehouse?

Yes, you may opt to collect your order from our warehouse although we don't charge for delivery to any destination on the island of Ireland!

warehouse collection