Single Mass Flywheel VS Dual Mass Flywheel – Is It Worth Converting?


Automotive flywheels have come a long way from their original design. As engines became more powerful and complex, so did this essential drivetrain component. Today most cars come with a dual-mass flywheel – a design that has proven to be incredibly efficient. However, more and more people go for a single mass flywheel conversion in search of simplicity and reliability.

Today we’ll try to find out which one of these solutions makes more sense and when you should consider converting.

What is Flywheel?

Although simple, flywheels were and still are essential for the operation of your average internal combustion engine. A flywheel is a component that is bolted to the end of the crankshaft. It’s a heavy disc whose purpose is to neutralize the violent torque pulses most engines put out.

Let’s explain that a bit further. All four-stroke engines deal with a torque spike in the power stroke. The reason for this is that this stroke is the only one that actually produces power. The intake, compression, and exhaust produce no torque relative to what happens during the power stroke.

This spike in torque causes all kinds of violent vibrations that negatively affect the engine if left ignored. One way to flatten that sudden spike in torque was to add a flywheel.

Flywheel (Dual-Mass)
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Rotating Mass

Adding a flywheel to the end of a crankshaft not only irons out the torque spike, but it also allows the engine to run much more smoothly. The rotating mass acts as an energy storage unit that takes all of those violent vibrations and dampens them significantly.

As engines became more complex and our need for efficiency higher, the vibrations and violent frequencies coming from the engine became more aggressive. We’ve reached a point where a rotating slab of metal wasn’t cutting it anymore. It is at that point that engineers invented dual-mass flywheels or DMFs for short.

Flywheel (Dual-Mass)
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Dual Mass Flywheel

The demands of modern engines have put a lot of strain on conventional flywheels. High torque, fast spinning motors have proven to be much less refined in terms of vibrations they produce. Managing these vibrations has reached the practical limits of simple flywheels. Adding more mass could eventually solve the problem, but it would only cause a different one. The more mass you add at the end of the crankshaft, the more energy you’ll have to expend to spin that mass up to speed.

Since that’s not feasible, automotive engineers have come up with the dual-mass flywheel. Just like its name implies, there are two masses inside one of these. These two separate pieces of the flywheel are connected by a pair of springs. Each spring usually features progressive tension, making it softer at the beginning of the compression and harder as it reaches maximum travel.

The idea behind dual-mass flywheels is to dampen the excess vibrations from the engine using this spring setup. As it turns out, this system works reasonably well.

Flywheel (Dual-Mass)
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The Downsides to Dual Mass Flywheels

Although highly efficient, DMFs aren’t without flaws. The increase in complexity means that you’re looking at compromised durability compared to an average solid flywheel. On top of that, when a DMF decides to go, it’s gone. There’s no refurbishing it as it’s effectively impossible to machine its surface with any measure of precision.

DMFs are expensive, and replacing one on older cars can put a serious dent in your pocket. The often prohibitive replacement price is exactly why some people are looking into single mass flywheel conversion kits. The real question is whether the money saved is worth it? Let’s find out.

Cutaway of a Dual Mass Flywheel

Single Mass Flywheel Conversion

Single mass flywheels are designed to replace DMFs by meeting the same or similar dimensions without internal complexity. Instead of having two masses moving independently, you now have a solid metal slab connecting your clutch with your crank. Installing a conversion kit isn’t necessarily hard either, which is another plus. However, it’s essential to understand the pros and cons of such a decision before you commit.

Flywheel (Single-Mass)
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Pros:

  • Price – It’s no secret that single mass flywheels are cheaper than their dual-mass counterparts. The sheer fact that there are no complex springs inside makes them easier to manufacture and hence less expensive to sell.
  • Increased Durability – Durability is always an important aspect when you’re discussing anything drivetrain-related. Single mass units are generally much more durable than DMFs due to their simplicity. If they eventually fail, there’s no risk of them falling apart, which can’t be said for the dual mass design.
  • Can be Machined – Another significant benefit of a single mass design is the ability to machine it when servicing the clutch. DMFs can’t be machined due to the way they’ve been engineered.

Cons:

  • Vibrations and NoiseSingle mass flywheels fail at everything a DMF was designed to do. No matter which conversion kit you get, you’ll experience a considerable increase in vibrations and noise during your daily commute. So much so that you might find going to work a grueling experience.
  • Potential Damage to Transmission and Engine – DMFs aren’t there only to improve your quality of life. A part of their mission is to protect the transmission and the engine from excessive vibrations. Once you go to a single mass unit, you’ll lose all of that protection, leaving your transmission and other parts of the drivetrain exposed to higher stresses.
Flywheel (Single-Mass)
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Is It Worth Doing the Conversion?

Switching from a DMF to an SMF will completely change the driving dynamics of your car. You’ll have to apply more gas, and your gears will feel different. Add the increase in noise and vibrations, and you end up with an experience that can get real old, really quick if you commute every day. While the savings might look tempting at first, the long term effect of the conversion is rarely worth it for an average driver.

That being said, there are applications where a single mass flywheel makes perfect sense. SMFs are rough at low RPMs and idle, but they are excellent when you spin them up to speed. That’s why you’ll often see them in track cars. If you’re building a project vehicle for track days or racing, an SMF could be a valuable asset. This type of flywheel can take the abuse of frequent launches and violent gear shifts. The same cannot be said about the dual mass unit. At the end of the day, the decision is ultimately yours.

Clutch Kit (4 Piecc) (Single-Mass)
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How to Find Quality Flywheels for your Car?

To find a quality flywheel for your vehicle, simply head over to our online store page and type your vehicle’s details into our navigation tool.

Our system will use that information to show you all of the parts and products that fit your car. If you have any questions regarding our selection of parts, whether the part will fit your vehicle, and more, give us a call. Our customer service is standing by to offer whatever help you need.

25 thoughts on “Single Mass Flywheel VS Dual Mass Flywheel – Is It Worth Converting?
  1. marcello pecci

    on a (US) 2012 audi a4 b8 quattro 6 speed manual, what can be expected to happen with the dual flywheel?

    I have an occasional judder on take off which I blamed bad motor mounts for. recently a mechanic said the mounts on these cars rarely go. I minimize the judder almost totally by using care and all my past manual clutch experience. Is replacing the flywheel the only option ?

    • Adam Goral

      Is it most prevalent in first gear? A jutter is usually the result of hot spots on a friction surface (flywheel) where the metal is basically heat treated from being very very hot. That causes uneven friction levels and generally a slight shudder when launching. When getting a flywheel resurfaced, the shop generally tries to cut deep enough to remove these spots, but because a dual mass flywheel can’t be resurfaced, it most likely will need a replacement. Try not to balance on the clutch at hill starts, and try to keep off the friction zone if possible in parking lots. Here is the flywheel for your car https://www.eeuroparts.com/Parts/59939/Flywheel-Dual-Mass-4150344100/ and the clutch kit is here, which includes everything you need including the hardware and slave cylinder. https://www.eeuroparts.com/Parts/75158/Clutch-Kit-02060/ It’s not cheap but our new Affirm payment method can help soften the blow on a purchase like that.

      Your car is too new for an SMF conversion it seems, but I assume in the next 5 years an OE style (not sport or racing specialty style) will arrive on the market. Good luck, and thanks for shopping.

  2. Venkateshwaran

    Hi I changed single mass cylinder conversion kit for Mitshibushi pajero 2008 but there is avibration in shaft .is there any solution to rectify the vibrations over shafts.if I use old dual mass cylinder there is no vibration.

    • Adam Goral

      A small amount of vibration can occur after an SMF conversion, as the original dual mass flywheel setup was designed specifically to create a smoother clutch experience. You have now deleted that setup. However, if it’s enough vibration to be concerned, I suspect wherever you purchased this part for your Mitsubishi did not sell you the correct part.

  3. mtbbob532

    I have 1200 miles on my Stage 1+ (375 hp/350 ft/lbs) 2017 Golf R. it slips in speed shifts from 3rd to 4th. I like the dual mass drivability so I’m looking at a stage 1 Sachs solid clutch, pressure plate and TO bearing replacement and sticking with the 1200 mile DM flywheel. Thoughts?

    • Adam Goral

      The Sachs Performance pressure plate and friction disk is a great way to bridle the power of a tuned engine while maintaining the factory feel of the clutch with the DMF. What you’re looking for is pure friction increase to avoid slipping and that’s what this would do. Keep in mind if you really thrash on it you can risk breaking a spring and trashing the DMF regardless of how much friction it can produce. We are actually in the process of adding Sachs Performance products to our site so your comment was in good time! I will edit this with a part number for future use when we add it.

  4. Roland Byfield

    I own a 2011 VW Amarok, which overheated due to a leak in the coolant system. when the engine was removed, I found out that the Flywheel was damaged. Which would you advise, a DMF or SMF?

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