Metal power clutch for MX-5 Miata


The carbon clutch made of advanced material is very outstanding. Even its price is reasonable. Thanks to the manufacturing process and method of construction the carbon clutch has a clearly high quality. We can recommend it to our customers with confidence.

On the other hand, if we talk about the metal clutch, we all remember that in the past it was mainly used for sports and races.

Let us explain here about the metal power clutch a little bit more.

1. Construction and suitability

Its components are the aluminum forged clutch cover, metal disc and the flywheel (F/W).


The picture shows the carbon power clutch. The metal disc has the same construction.

The flywheel’s weight is around 3.7kg. The whole system’s weight is 8kg.
The 3.7kg weight is almost half of the genuine F/W’s weight.
It is designed for running.

The release bearing and the center pilot are not attached, but you can purchase them as separate items.

2. The shape


The metal disc of the power clutch has 6-wings.
Usually a permeable metal disc has 3-wings.
You might think that with the 6-wings disc it becomes harder to drive.

In the case of the 3-wings disc the friction force is high and if you don’t adjust the wings' number well, the clutch meat becomes difficult and you might get into a difficult situation on the streets.
For this reason we set up a spring that has the function of a damper and eases the shock at meat time.
In the case of the power cutch, which has 6 wings, the spring is removed.
Even with this procedure the clutch meat should be difficult. However, in reality we can operate the clutch very easily.
The reason for this lies in the metal material.
Avoiding a material with high friction force, we use a material that can “slide” to some extent.
While thinking of the disc’s setup we have to find a balance between the meat time and the lock time.
If we can get some “sliding” during the meat time then the starting becomes easier.
At the lock time 100% transmission is maintained.
This is our ideal.
However, it is quite difficult to get this result.
We have to consider the compatibility (crimp power) with the clutch cover (pressure plate) too.


In the case of 3-wings we use a slightly strengthened genuine clutch cover to the genuine flywheel. In this case the crimp force is 100kg more then the standard.
The cover’s spring lever is the same as in the case of the genuine one, for this reason even if the crimp power is 100kg more, it reflects on the clutch pedal. This means that the pedal becomes heavier.

To heighten the lift amount with this 100kg up, we have to heighten the disc’s friction too.
If we heighten the friction then to some extent we can even heighten the lock amount.
However, the friction is high, that’s why the meat becomes difficult, so we have to lower the number of the wings and set up a spring to ease the shock.
After this the situation is as follows: a heavy pedal, heavy disc, abrupt meat, some crimp power up (clutch cover).


In the case of the 6-wings disc, we use the 1,000kg crimp force (2 times more than the genuine one) forged cover to lock the power clutch properly.
In this way we get a wider half-clutch and with the change of the cover’s spring lever ratio we get a lighter pedal and an easy meat-control.

A light pedal, light disc, easy meat, 6-wings clutch face, the biggest possible disc axis. These are the things that secure the crimp force (1,000kg).
These are the features of our metal power clutch.

For further information about the tread force check out this page.

3. Construction

There are many users who worry about the weight of the flywheel, but not as many users worry about the disc’s weight.
The flywheel affects the running (pickup), but it’s being affected by the disc’s weight too.
The reason for this is, that both the cover and the disc rotate together with the flywheel.
This means, that the light weight of the disc affects the whole clutch system’s weight. Furthermore, the shift-change has an important effect too.
The disc rotates together with the transmission main shaft.
Thanks to the reduction of oscillation and inertia even at high rpm we can get a fast shift change.

The disc is being connected with the mission through the spline.
It is crimped to the flywheel and the clutch cover and torque is being transmitted to the disc.
The light weight of the disc affects the mission’s inside.

4. Lightness

In the case of metal there isn’t as much abrasion as in the case of the genuine one (non-asbestos material), however there are cases when the edge looks like it has been cracked or chipped. The reason for this is the thickness and high level of friction.

For adjusting the thickness to the genuine shaped F/W and cover, we need the same thickness as that one of the genuine clutch.
The genuine disc’s thickness is 8mm, however we have to consider the durability while controlling the lock and release position by the stroke and deciding the disc’s thickness.
This is the reason for a more than necessary thick disc used for tuning.
Furthermore, as we already mentioned before, to ease the shock at meat time a spring damper has been used as an intermediary and the disc becomes not only thick but heavy too.

You can see that it’s better to buy a system kit that contains F/W and cover too than to purchase the metal clutch bar and disc separately.

5. The transmission

As we already mentioned before the lightness of the disc affects the shift change a lot.
Our engineers tried to lighten it even with just 1g, without losing its durability.
Its effect lies in the fast shift change and in the background stands the lowering of the gear and synchronizer’s load.
We get a light, flattened clutch disc that can disengage.
This is a very important point.
Usually while driving, a strengthened clutch gradually loses its ability to disengage and in the second half of driving at shift change you can hear a loud grinding sound. This means, that the disengagement is getting bad.
Many users think about this phenomenon as a damage inside the mission, however in reality the reason might be the bad clutch disengagement.
The metal of the power clutch is almost as light as the carbon disc, it decreases the rotating gear’s and synchronizer’s burden and based on the weight reduction and flattening, we can get a disengaging clutch.

6. Durability

The weight of the disc is only 800g.
It is extremely light, so you might not be sure about its durability, however note that similar discs are being used in the shape of twin or triple in Nissan’s GT-R.
Strong supercharging, intensive power, only a little bit heavy car. This kind of safe product is being used in Miata/MX-5 too.
Furthermore, the 1,000kg cover grip force is the same as that of high power cars (turbo cars).

7. Usage

“I just want to drive on street roads. Can I use an ordinary clutch?”

We get these kinds of questions very often. Undoubtedly, that’s right – it is enough for users who drive under usual conditions to use a genuine clutch. All those who want to continue driving just as up till now, don’t need a strengthened clutch.
However for those, who think of pickup, we recommend to use the light flywheel together with the power clutch.

The power clutch is a part for those users who are aware of driving.
It doesn’t mean that it’s only about circuits. It has a very good effect on crests too. In the case of a light clutch system including F/W, not only the pickup gets better, but the engine brake’s effect improves too.
The reason for this lies in the fact that heavy rotating things have a strong inertial force that makes them rotate as long as possible. On the other hand the lighter something is, the easier it is to stop it. In other words, the engine brake can be effective very easily.


This is a rough picture of the flywheel.
To get the heavy flywheel into movement we need power, but as soon as it starts moving, it cannot be stopped easily.
In other words, the speeding is not too good and the engine brake can’t be effective easily.
Its advantage is that the accelerator work cannot be easily affected and the car can be driven by anyone.

The acceleration of the light flywheel is very good and the engine brake can be effective easily.
In the case of sport driving lightening of some extent is very attractive.

It is a clutch that enables you to enjoy driving. We recommend it to all those users who run on circuits and races too.

8. Price

The flywheel and the forged aluminum cover make a total set. The price is very reasonable.

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Maruha Motors Co., Ltd.
Ushizuma 2095-6, Aoi-Ward
421- 2106 Shizuoka city, Shizuoka prefecture
Japan
TEL: 0081-54-294-0076
FAX: 0081-54-294-1312
E-mail: info@maruhamotors.co.jp