Dual mass vs single mass flywheels

Left – Single Mass Flywheel Right – Dual Mass Flywheel

Exedy is one of the world’s leading producers of performance sports and racing clutches, so when it comes to explaining the differences between Dual Mass and Single Mass Fly Wheels, Australian Automotive Aftermarket Magazine spoke with Exedy Australia Senior Product Manager, Mark Davis.
“The Dual Mass Flywheel derives its name from the two main components, or masses, that operate independently of each other,” Mark says.
“The primary component, or mass, is fitted with a ring gear and sensor ring, if applicable, and is attached to the crank shaft.”
This primary component usually incorporates a dampening mechanism typically made up of torsion springs and friction washers that are ideally suited to absorbing torsional vibrations within the drivetrain.
“The clutch unit is then bolted onto the secondary component. Quite simply a DMF is a damper for your drivetrain,” Mark explains.
Dual Mass Flywheels can fail for a number of reasons, but the most common cause will be wear and tear.
“Like any other component on a vehicle, Dual Mass Flywheels will wear out over time,” Mark says.
“But other causes of failure may relate to driving technique, overloading the drivetrain when towing or increasing torque to a point where it exceeds the torque capacity of the flywheel.”

Flywheel specifications vary from manufacturer to manufacturer and as such, there is no one test that indicates whether the flywheel has reached the end of its service life.
There are however some generic tell-tale signs that indicate to the installer that the flywheel should be replaced such as grease or oil leaks, or noisy operation.
“The safest option is to replace Dual Mass Flywheels each time the clutch is replaced,” Mark explains.
“Furthermore, we strongly recommend that you do not grind, machine or attempt to repair Dual Mass Flywheels.
“These actions are fraught with danger as it is not possible to machine or grind the flywheel surface accurately without removing the secondary component from the primary mass. Attempting to machine and rebuild a worn DMF will usually result in the premature failure of not only the flywheel but the new clutch set as well,” he adds.

The replacement of a worn Dual Mass Flywheels DMF system with another DMF and clutch package is an obvious option, however, the cost of this option is sometimes prohibitive. As such EXEDY has developed a range of Single Mass Flywheels (SMF) which are sold together with the clutch cover assembly, clutch disc and release bearing to replace the DMF clutch system.
“The main advantage of the SMF clutch package is the price,” Mark remarked.
“These systems are generally cheaper to purchase. Furthermore, as the SMF has no moving components, they can be machined and re-installed into the vehicle when a subsequent new clutch is fitted thereby reducing the future cost of maintaining the clutch system.”
The conventional SMF is extremely robust and is, for example, the preferred choice for vehicles used in racing or commercial applications.
While the SMF replacement clutch system is a popular choice, it is however important to note that despite the durability and price advantages, theses system do not possess the same dampening characteristics as a DMF and on occasion, may not sound or feel like the DMF system that is being replaced.

“Therefore, when recommending a replacement clutch and flywheel system you should communicate to your customer the pros and cons of replacing the DMF or of fitting an SMF in its place,” Mark says.
“This will enable your customer to make an informed decision regarding which replacement system best suits their budget and needs,” he adds.
Founded in 1923 Exedy has built a reputation supplying industry leading powertrain products.
The company claims its pursuit of perfection and assurance of safety are underpinned by quality and reliability.
Exedy’s advanced engineering and patented innovations have seen the organisation grow into a leading manufacturer in the world for clutches and other powertrain components.

For more information visit www.exedy.com.au