There are a variety of options when looking for a clutch to take the new power you’re making in a turbo setup or even if you’re looking for a more performance orientated upgrade.
We’ve tested various manufacturers at each price point over the years and have settled on a core offering that we know from testing in both daily driver and motorsport works consistently for various power levels.
What are you looking for in a clutch?
Kind of like the old adage of building a car, you have 3 options ‘Cheap, Fast, Reliable’ – clutches have a similar set of three rules. ‘Power, Drivability, Cost’.
Let’s start with Power, with a single disc setup we have to rely on the pressure provided by the clutch pressure plate and the friction coefficient of the material the clutch disc is made from, the balance of these two factors work together to give you the driving experience.
For example, your typical choices are;
These are normally full face clutches that use the entire face of the clutch to mate to the flywheel, spreading the load evenly across the surface with normally a relatively normal pedal feel, from the pressure plate.
You can increase the clamping force of the material with a harder pressure plate, giving you a stronger left leg over time and generally making start-stop traffic a recurring nightmare.
The Competition Clutch Stage 2 Clutch uses an organic material with, in our opinion, better than stock feel, and has been tested by us to handle ~200ftlbs of torque to the wheels. It’s a great choice for most builds using small frame turbos like the T25 or TD04.
The ACT Extreme is also comparable with a specific and higher torque rating than the competition clutch stage 2, it does have a somewhat heavier pedal feel but is just as street able.
This is the next phase of improving the friction of the disc, for a similar amount of clamping force as an organic style clutch you can achieve better torque holding.
These can come in many shapes and sizes but the typical examples are called segmented ceramic as they utilise many segments, while not using the whole face of the clutch like the organic they are using ~70% of the available space.
A point to keep in mind here is that the smaller the area you’re applying the force, the better the clamping load – this is counter-intuitive but think about how you could use a really thin cable tie on a hose, it will deform and crush the hose far more than a thick one – because the clamping force is concentrated in the smaller area.
In the world of clutches, this means higher power loading but does make the clutch itself more ‘grabby’ as it becomes closer to an on / off feeling.
We’re happy to say that the Competition Clutch Stage 3 Clutch maintains a feel very similar to the stage 3, allows you to slip it in traffic and is very forgiving with excellent power holding capacity, tested at over 220ftlbs to the wheels but we would see little reason this couldn’t hold 250+.
Puck / Ceramic
The typical name for this type is a ‘button ceramic clutch’, it goes another step further with the friction material and design using 6 or 3 individual buttons or pucks (6 puck clutch, for example) and often a very strong pressure plate.
This type of clutch is always the harshest to use, with the action being very ‘on or off’, difficult to slip in traffic. That’s why this is typically recommended only when the power of the car warrants it and in our testing, that’s a car making over 300hp. Like our EFR 6258 build.
This is the strongest offering from our preferred suppliers and going much further than this type of clutch starts to test the rest of the MX5 / Miata’s drivetrain, even a 6 speed box will start to have a hard time at the 300hp+ power level.
For example, the Competition Clutch Stage 4 is a 6 Puck Clutch, which we have had great experience with – ACT offer both a 6 puck and a 4 puck if you’re really pushing the envelope.
Best of Both Worlds?
Does such a clutch exist, is there a happy medium between a reasonable torque holding clutch and one that doesn’t rip your leg off?
The OEMs seem to manage it, 6 speed manual Lamborghinis were a thing and they seemed to be OK.
Well here you have it.
The performance clutch you don’t “have to get used to”.
What do we mean when we use the word ‘driveability’ – typically the manufacturers remit for clutches is to ensure they have a reasonable lifecycle, typically 60,000-100,000 miles. Requires minimal effort to engage with a reasonable feel and biting point.
We’d want to maintain as much of that stock feeling as possible, within reason. Some of the drawbacks of this remit are that the clutch engagement can be lazy or perhaps not provide the feedback you’d want as a spirited driver.
They also are simply built to take roughly the power that the stock car makes, now there are always exceptions to this and typically the stock clutch will slip quite dramatically around 180hp, which is a considerable bump compared to the stock 130hp for the 1.8s.
Our remit when looking for performance clutches is to ensure the power can be transmitted first and foremost, as frankly, this is the reason these compromises need to be made in the first place – second is that they’re easy enough, or at least not tiring to use in traffic.
Other considerations are noise when moving off, initial slip or chatter and how dramatically the clutches bite – as this can be quite a pain in the winter.
All the clutches in our lineup provide enough drivability for each power bracket – if you’re daily driving a 300hp MX5, the chances are you have a quite advanced clutch and car control and can handle it being a little grabby.
A clutch may seem like an irritating and necessary evil on your journey to a properly fast MX5, they take time to fit and offer up a world of ‘while you’re in there’ moments. A couple of those that should not be skipped are these…
We always recommend 1.8 clutches – Why? Because they are physically larger than the 1.6 clutch system and to support the power quoted we need to make the most of the system.
This means, if you have a 1.6 car you’ll need a new flywheel – it’s great because they are completely bolt on with no downsides, however, if you’re looking to maintain the 1.6 flywheel, ACT offer an excellent range of 1.6 compatible clutches in various materials.
The clutch is only as good as the flywheel – Loads of stories of clutches being chattery or not holding power or generally slipping when they shouldn’t be are down to the flywheel. The ceramic clutches are especially prone to this and need a good clean mating surface.
We would always recommend buying a new Lightweight or Ultra Lightweight flywheel, now you might be thinking that’ll change the car and make it more difficult to drive, however. If you weigh a stock 1.6 clutch and flywheel and a 1.8 you’ll find that once you put a comp clutch and ultra flywheel on, you’re not much lighter than the stock 1.6 system anyway – doing this on a 1.8 makes it zing through the gears as an MX5 should.
With that being said, if this is a little out of your price range consider that your flywheel must be resurfaced in order for the clutch to be warranted, often this task can justify a new lightweight flywheel.
Change that rear main! – If you contaminate the gearbox bell housing with oil mist from your rear main seal leaking, your clutch will fail. It will slip and it will leave you with the job of replacing it again, they can be cleaned but generally aren’t the same again.
You’ll probably want to change your gearbox oil – Pulling the gearbox inevitably means spilling the oil out of the prop shaft side, it’s reasonable maintenance to budget with the change.
Expect a clutch change to be around 3 hours worth of labour if you’re having a shop do the job, if you’re doing it on your back in the street budget most of the day and start early.
Hopefully that’s a helpful introduction, if you have any specific questions or would like advice for your build then please get in touch with us via Facebook, Email or Telephone available on our contact us page, we do our best to select products based on real-world testing, if we offer it for sale, it’ll work as advertised.