There are two primary points in time where you will begin shopping for a clutch: replacing the worn out one in your car or truck, or upgrading to a performance version. As you approach the market though, you’ll find that there are a lot of options out available to you. Additionally, the terminology can be confusing—as can the marketing.
The most important part of the decision-making process is choosing a clutch that matches your demands. But since most drivers’ demands are pretty multi-faceted these days, it can be difficult to nail down the proper clutch for each and every installation. We reached out to Will Baty or “Mr. Clutch” at Centerforce Clutches, the leading manufacturer of performance clutch and pressure plate systems in the United States, for some guidance on the topic.
Before you begin shopping for a clutch, it’s important to nail down what the overall intended purpose of the vehicle is. Is your vehicle primarily a daily driver? Or does it see more off-road trails than pavement? Is it serious street? Track? Each clutch has its own pros and cons, so determining your style of driving will determine your style of clutch.
Additionally, Baty says that when helping a customer choose a clutch, there a few things he likes to know. “What is the reason for needing a clutch? Did it just wear out? Is the vehicle producing more power than the clutch can handle, or was there a failure? If there was a failure, we want to find the reason and get it fixed BEFORE new parts are purchased.”
Clutches are in direct contact with the engine’s flywheel and will have to work against the power of the engine. Because of this, engine output is going to play a major role in your decision. You want a clutch that will have enough bite to it to manage that power, as well as withstand the abuse it will take during use. Though, even if you have a ton of power you want to be cautious of putting performance clutches on street-driven vehicles.
Street vs Track
Clutches designed to withhold high-power output usually have stiffer springs. This helps prevent clutch slip and is ideal for precision driving. However, the lack of slippage makes inching up more difficult. You can use performance clutches on street cars, but you want to be aware of the difference in engagement, as it will have an impact on how the vehicle performs, even at low speeds.
Baty advises that you “be honest with yourself on what you want from the clutch and the intended use of the vehicle. A drag racing clutch is going to need a material that recovers quickly due to the extreme heat that a clutch can be exposed to. The weight, gearing, and power output help determine which clutch will work the best for the application. Most of the street clutches will be using a type of organic friction material which will provide nice drivability, versus a drag racing clutch that in most cases use a cerametallic friction material which may have an on/off type quick engagement with possibility of chatter,” he says.
While torque and driving styles both tell you what you will be demanding of your clutch, the friction materials tell you how that clutch will handle the workload. As Baty points out, different materials provide different types of engagement. And while there are thousands of different materials in each configuration, there are three main types on the market: Organic, Kevlar, and Cerametallic.
Organic material clutches use a woven material with resin consisting of metallic flakes and rubber. Being the softest option, they resist chatter well but require more frequent replacement. This makes them an entry-level clutch ideally suited for stock or moderately-powered street cars, but a poor choice for high-power applications. Since they offer nice all-around strength, durability, and smooth engagement, they are often found on OEM applications.
“You will find several different types of material used with our organic material,” says Baty. “This material can be heat-sensitive, so excessive slipping is a No-No. We use a carbon-based material with other fibers impregnated into it that has a nice recovery when exposed to excessive heat.”
Kevlar is exactly what the trademarked name implies. These clutches are harder, offering smooth engagement over a longer lifetime. Kevlar clutches will provide more chatter than organic facings, but they can handle much more heat, making them a great choice for car owners with a lot of power who intend to drive their car on the street and sometimes the track.
“Kevlar, has a high-burst strength ideal for very high RPM vehicles. What the Kevlar doesn’t have is a high point of friction. This material relies on a pressure plate with high amount of clamp load. In most cases, the Kevlar won’t have the holding capacity of the Organic friction material,” says Baty.
Primarily designed for racing applications, cerametallic clutches are the hardest. “Cerametallic is basically a high-copper based friction material impregnated with other materials,” explains Baty. “This material actually likes heat; it’s designed to work in an elevated-heat environment with little wear. But the trade off can be chatter, and if it is exposed to too much heat it will weld itself to the flywheel or pressure plate.”
Ideally, when shopping for a clutch, you won’t have to worry about balancing materials, design, and driving styles in order to match a clutch on your own. Most aftermarket suppliers offer clutches in stages, with each one designated to power demands and driving style. Often, there are five stages; think of them like a spectrum. A stage one clutch is the low point, designed to handle moderate power and a stage five being able to hold maximum. Not all suppliers follow this method, but they do usually have their own take on it. However, it’s still worth familiarizing yourself with the technology and materials behind the designs in order to make the right choice for your application.
Baty explains that Centerforce actually offers seven different stages. This is a great chart to keep for reference going forward!
|An upgrade to the OE-clutch intended for a daily driver with mild to no performance upgrades. It utilizes a full-face, high-quality friction material on both sides of the disc.|
|Centerforce II||Utilizes the same disc as the Centerforce I, but in most cases has more centrifugal weights and clamp load. Intended for mild performance upgrades and off road vehicles.|
|Dual Friction||A single disc with two different friction facings, coupled with our Ball Bearing actuated pressure plate. This is our number one selling assembly. The Dual Friction has a high-holding capacity with great driver control. Works great with higher performance applications without sacrificing drivability.|
|DFX series||This is our high-performance assembly, featuring a Cerametallic friction material coupled with our Ball Bearing pressure plate. Works great in a drag racing environment or big-power, heavy, off-road vehicles running in the Baja environment. Drivability may be compromised with this assembly.|
|LMC (Light Metal Clutch)||Low-inertia, Aluminum Ball Bearing actuated pressure plate with a replaceable friction surface. The LMC disc is an organic dual puc style disc for increased holding capacity. Intended for a circle track, autocross or track related environment. Available in 10.5” & 11” diameters.|
|DYAD Twin Disc||Features a twin/dual disc assembly offered in 8.750”, 10.5” and 11” diameters. The DYAD features our Ball Bearing pressure plate with our patented true twin sprung hub disc assembly. This is a fully blue-printed, balanced assembly available in either Organic or Cerametallic friction materials. The DYAD was designed for the enthusiast that is producing some serious power but doesn’t want to sacrifice drivability. The DYAD has a holding capacity range from 500trq – 1,700trq (depending on size and series).|
|TRIAD Triple Disc||Very low inertia assembly offered in a 8.750” diameter. The TRIAD features our Ball Bearing pressure plate coupled with a unique triple disc assembly. This is a fully blue-printed balanced assembly available in either Organic or Cerametallic friction materials. The TRIAD was designed for the enthusiast that is looking for a very low inertia assembly with nice drivability with excellent driver feedback. This assembly works great for an autocross or road track environment where a low inertia assembly is beneficial. The TRIAD has a holding capacity range from 500trq – 1,200trq (depending on series).|
Consider Your Flywheel
With all of that said, the clutch is like a big brake pad and the flywheel is like a rotor. The two surfaces will wear, and installing a new clutch on an old flywheel can bring up issues on its own, such as excessive wear and slippage. The flywheel can warp and even crack after prolonged use. So, between each new clutch install, you’ll want to check the condition of the flywheel. For minor grooves and wear, resurfacing the flywheel is an option. If, however, the flywheel is warped or even cracked, you’ll want to replace the unit altogether.
Centerforce provides several options, from simple OE-replacements to exceptionally light flywheels offering maximum weight and inertia reduction for enthusiasts seeking optimum performance. However, Baty cautions that, “Like everything, there is a trade-off when selecting a light flywheel. I tell people ‘Inertia is your friend.’ If you go too light on a flywheel, your car will bog or stall very easily if your vehicle is not set up for that lightweight flywheel. When you reduce the weight/inertia of the flywheel, the weight of the vehicle will pull the engine down easily when trying to take off from a dead stop. (Lower gears, larger displacement engines or lighter weight vehicles can help combat this issue.) The lighter weight flywheel is nice on a road course where you can take advantage of engine braking because of the reduction in rotating mass/inertia,” he finishes.
Installation and Cost
At the end of the day, a new clutch with the cost of a new flywheel and installation will run upwards of $1,000. Of course, this can vary with the options selected and who you go to for the installation. Fair warning, though: you really don’t want to pinch pennies here, as the clutch is an extremely important part of the vehicle’s operating system.
Purchasing the wrong clutch can result in a myriad of problems, like over- or under-clutch. But a botched installation is downright dangerous. “Knowing your intended use is important,” Baty reiterates. “Finding a shop you trust sometimes can be challenging. Do your homework! Remember, you don’t want a “job shop,” you want a shop that will stand behind its work. Someone who actually cares about the type of work they do… what we call ‘Pride in your work.'”
Of course, you can save money by tackling this job yourself, but there is a lot to learn if it’s your first time. For some pointers on the installation process, check out our piece: The ABCs of Clutch Installation.