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Dual Mass Fly Wheel

Since its launch in 1985, the LuK Dual Mass Flywheel (DMF) has been fitted as original equipment in ever-increasing numbers of vehicles.


When a conventional single-mass flywheel  and conventional clutch reach their torsion angle limits at around 18°, the DMF, with its decoupled dual masses and a torsion angle of up to 100°, can absorb much more oscillating energy.

Today, every second passenger car or light commercial vehicle which rolls off the assembly line is equipped with a DMF – and the growth is still increasing. The trend towards more engine torque and lighter vehicles ensures excellent prospects for the DMF as it offers just what the market needs: more driving comfort and reduced fuel consumption. With the increasing market share in the OE sector, the DMF’s business potential in the aftermarket is also growing.

To date, almost 60 million Dual Mass Flywheels have been produced by LuK.  The majority of these have been fitted as original equipment to the most popular vehicles that are used on the roads in the UK.


The DMF provides technical benefits manufacturers cannot ignore, hence its movement toward being a standard component of a car. As a supplementary part of the clutch, the DMF is positioned between the engine and the transmission to neutralise vibration, thus meeting the ever greater demands for smooth running, driving comfort and fuel efficiency.

Traditionally this job has been done by the springs in the clutch driven plate, but recent developments in automotive technology have meant that other means of dealing with the problem of vibration have had to be investigated.


Every time an engine fires, a shock occurs creating what is commonly referred to as ‘Noise, Vibration & Harshness’ (NVH). This is transmitted down the crankshaft and into the transmission.  In addition to this, any moving parts bolted to the engine will contribute to the overall NVH generated by it.

An example of a contributor to NVH is the air conditioning compressor, where NVH is exacerbated by climate control causing the compressor to continually switch on and off as it regulates the temperate within the passenger compartment.

Lighter engines contributing to better fuel economy, combined with higher combustion pressures to lower emissions increase the torsional vibration emitted from today’s engines and conventional clutch plate dampers cannot meet customer aspirations in levels of comfort.

Why do we need to minimise these vibrations? 

If not dealt with the NVH will travel into the gearbox leading to premature wear and failure. In turn it will then be transmitted into the cabin of the vehicle, leading to reduced driver comfort and in the cases of vehicles that are used all day every day, potential injury. 

In an increasingly litigious society, companies that operate fleets need to be more careful than ever before regarding the vehicle in which they send their employees out.  Likewise, they will be acutely aware of the cost of vehicle down time and should be doing everything they can to avoid such situations.

The Need for Awareness

Component manufacturers have a duty of care to educate their customers, who in turn need to do so with the people who buy off them.  These lines of communication have never been more open.  With the number of premises in the UK having broadband on the increase, the block exemption laws and the ‘Right to Repair’ campaigns, in theory at least, should expand the amount of information available to a garage or factor.

Despite all of this however, there are still many people in the UK aftermarket who do not fully understand DMF technology and, more importantly, how to remain profitable when dealing with them.

A main symptom of a worn DMF is clutch failure in the form of engagement problems or clutch slip. If a worn DMF is not diagnosed, a clutch replacement may cure the problem in the short term.  However, it will not be long until the same issue occurs, which in turn can lead to customer dissatisfaction and expensive warranty claims.


Whenever replacing the clutch, the DMF should always be tested for wear. Simple checks can avoid further problems later on and even generate more profit from what is usually a very labour intensive job.

Normal flywheel checks also need to be considered.  If the surface is cracked or blue, indicating that there has been excessive heat transfer, then replacement is advised.

DMF Testing Tool 

Enables testing of a DMF’s functionality whilst the part is still on the vehicle.

Using this, the freeplay of the springs and rock of the bush or bearing can be accurately measured and compared with part number specific tolerances.

There are an increasing amount of DMFs that have a Friction Control Plate (FCP).  This device provides additional damping on start up of the engine and when the load on the DMF changes.  Where an FCP is present, the DMF tool is needed to test the freeplay.

Dual Mass Flywheels remain a relatively new product group and as such, supplier's still own the patents on specific part numbers resulting in captive parts for those who are OE.


The Dual Mass Flywheel is a product of vehicle evolution.  It is a solution to the problem of excess vibration created by modern motoring standards. It is always necessary to test the DMF for wear every time the clutch is replaced.  Failure to do so could lead to expensive premature clutch failures.

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