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One of the worst things you can do for performance is neglect to pair your engine's power upgrades with the right clutch. At the very least, a mismatched clutch may fail to engage and, at the worst, it could blow apart during power shifts. An improper clutch can also let a lot of potential power simply go to waste.
Don't worry-- we're not about to turn clutch selection into rocket science. While it's certainly worth it to learn as much as you can about this segment, the aftermarket has made quick work of selecting the right one for your combination. That said, there are some key details that will make your life easier. We're here to lay out the basics of clutches and what you need to know about them when you start building a ton of power.
How Does a Clutch Work?
For starters, let's look at the clutch's role in the driveline. The clutch's job is to transfer power from the engine to the transmission. It's a system made up of multiple components, with the pressure plate and clutch disc being the two main players.
The entire clutch assembly is fixed to the flywheel of the engine. The pressure plate bolts to the flywheel, with the clutch disc sandwiched between them.
The flywheel is fixed to the crank with bolts, while the clutch disc fits to the input shaft of the transmission via splines. When the clutch is engaged, the pressure plate pushes the disc tight up against the flywheel. The clutch, being made of a friction material similar to a brake pad, is then able to transfer rotation of the crankshaft. As you depress the clutch pedal, the throw-out bearing presses on the pressure plate, disengaging the clutch, and allowing you to shift.
An Aftermarket Clutch Upgrade is Key for Big Performance
The clutch exists in an incredibly violent environment where it's forced to contend with power from the engine and resistance from everything else down the line. As torque, horsepower, rpm, and traction increase, it becomes harder and harder for a clutch to do its job.
Clutch failures can spell big trouble in a number of ways. Slipping clutches can lead to engine failure; they can soak up horsepower before it reaches the tire and cause a number of other issues. That's why you need to pick a clutch that's capable of standing up to increased power levels, harder driving, and especially racing.
There are a few ways to build a clutch to handle those conditions. In any case, it starts with improved friction.
Manufacturers can improve friction in a number of ways. For a mild build with just a little more power than normal, a single disc clutch with improved friction materials is a viable solution. As you increase to more radical numbers, increased disc counts can help dramatically increase the torque handline capacities of a clutch.
Double-, triple-, and even quadruple-disc setups are available for extreme applications. Naturally, a more robust setup to contend with harsher conditions follows.
Which is the right combination for you really depends on the application. While you should always upgrade your clutch when power is increased, how big you need to go depends on the power level you started with and where you're taking it.
Thankfully, top brands make it really easy to determine what's best for you. Most of them even bake in power ratings and intended use right into the part description. Industry leaders to keep an eye out for while you shop for clutches are Centerforce, McLeod, Ram Clutches, and Exedy. All of these brands build excellent clutches and flywheels, and bend over backwards to make sure you have the right clutch in your ride.
Clutch and Flywheel Weights
You're bound to hear about clutch and flywheel weights being emphasized as you shop around. That's because rotational mass can totally define your driving experience and have a dramatic effect on performance.
In terms of all-out performance, lighter is better. Lower rotational mass makes it easier for the engine to rev, which can help it produce more power sooner. In a high-traction racing scenario, every little bit counts so going as light as possible is ideal as long as it doesn't compromise strength.
On the other hand, higher rotational mass slows things down a bit. This might sound like a detriment, but this makes an engine more predictable. It can improve your driving experience in traffic and around town and can even offer an edge in low-traction racing situations.
Which is best for you, again, depends on how you use your vehicle and the conditions you primarily subject it to.
What’s the Deal With Hydraulic and Mechanical Clutches?
The terms “mechanical” and “hydraulic” clutch get thrown around a lot. It can be easy to fall under the impression that hydraulic is some huge performance upgrade that you need to have on your car, no matter what. However, these terms have nothing to do with the clutch itself. Instead, it refers to the throw-out bearing.
Throw-out bearings operate either mechanically with links and cables, or with hydraulic assistance, which is provided by a master cylinder, just like on your brakes. The difference is that mechanical clutches are a bit stiffer and harder to operate, while hydraulic clutches are smoother and easier on the leg.
A lot of people upgrade to hydraulic clutches for sheer luxury. It makes that old manual much more enjoyable to drive. They also make running high-performance, heavy-duty clutches a lot easier, and are highly beneficial to applications that use them. However, mechanical clutches are still plenty viable, and have the edge of being mechanically simpler and more affordable.
How Hard Is It to Install a New Clutch?
Installing a new clutch is something you can do in your own garage with a few specialty tools and some education on the nuances of your particular setup. Really, all you will need are some basic hand tools and a jack and jack stands, along with a torque wrench, a clutch alignment tool, and a transmission jack.
You can even change your flywheel at home; just remember to use thread locker and to torque everything to spec, as forgetting can lead to the assembly coming through the floorplan like a buzz-saw.
Things get a little more complicated if you're upgrading from a mechanical throw-out bearing to a hydraulic system. This seemingly simple component is reliant on a lot of specialty tools and it’s essential to get everything just right, or you will wind up taking it apart over and over again until you do. Still, many people do perform this in their own garage, just with plenty of research done ahead of time.
The Clutch Is Just One Link in the Chain
Just like neglecting the clutch is a big mistake for high-horsepower builds, the same is true for everything down stream of it. It's important to remember that a driveline is only as strong as its weakest link. A harder-biting clutch only guarantees more stress on everything from the transmission to the wheels.
If you're building enough power to warrant a stronger clutch, then you should research your application and determine what other parts of the driveline aren't up to the power you're producing.
Input shafts, transmission internals, U-joints, driveshafts, axles, carriers, and even axle housings can all give out under extreme loads. So, take your time, make the right upgrades, and you can enjoy that hot rod as much as you want without worry.