Whether they're organic or metallic, the materials used on a clutch disc impact clutch bite, streetability, and longevity. "Organic compounds are more widely used from the factory, and are made of various fibers, resins, and other additives," explains Baty. "They offer very smooth engagement, but deteriorate very quickly when subjected to heat. Ceramic-metallic compounds tend to be more aggressive, typically have a greater holding capacity than organic linings, and are made by sintering different metals together-much like a brake pad. These compounds have a high coefficient of friction but tend to have a shorter lifespan."
Certain clutch designs are more prone to chattering when engaged than others, but it's often caused by installation errors or other faulty areas of a car. Baty suggests checking the clutch disc for contamination by oil, hydraulic fluid, or grease. "Other potential culprits are an improperly resurfaced flywheel, or a bent clutch disc or pressure plate," he explains. "Chatter isn't always caused by the clutch system, either. Loose or damaged engine and trans mounts, or mounts that are too stiff, can cause chatter as well."
"Stock pressure plate and flywheel bolts can be reused as long as they are in good condition. We suggest using some type of thread locker on the flywheel and pressure plate bolts and to tighten everything back up to the factory torque specs. Aftermarket bolts can also be used, but we strongly suggest that you use bolts designed specifically for pressure plates and flywheels. You shouldn't go down to your local hardware store and buy some Grade 8 bolts and expect them to work. For example, the 3/8-inch pressure plate bolt commonly used on GM vehicles is a small-shouldered bolt. The shoulder fits snuggly into the pressure plate boltholes and goes into the flywheel, centering the pressure plate to the flywheel. This is critical for proper balance of the engine. The shoulder also takes some of the shearing force when the clutch is engaged. Some flywheels use dowel pins to center the pressure plate and absorb this force, but it's still advisable to use a small-shouldered bolt."
With new car manufacturers transitioning from cable-actuated to hydraulic clutch systems, the challenge for the aftermarket is increasing clutch bite without the luxury of significantly increasing pressure plate clamping force. It's a problem that requires innovative solutions. "Many modern hydraulic systems seem to be marginal when simply trying to operate the stock clutch," says Baty. "That is why we pay very close attention to the throwout bearing load, which is the amount of pressure it takes to operate the clutch. Some clutch manufacturers change the diaphragm or machine the fulcrum point to increase the clamping force of the pressure plate. This, unfortunately, increases the throwout bearing load and leads to hydraulic system failure in some vehicles. Consequently, we utilize our patented ball-bearing procedure that allows us to decrease the amount of pressure required to operate the clutch."
A botched install is the quickest way to destroy a clutch. According to Baty, the most common mistake is not checking to see why the original clutch failed. "If you have a leaky oil seal and put a new clutch in, you're just going to ruin the new clutch with oil in a short time, so we advise our customers to always check and inspect every component in regard to the clutch and driveline when replacing a clutch," he explains. "Also, people often use too much grease on the input shaft. Remember the input shaft spins with the engine so the grease will eventually reach its way to the disc. Our suggestion is using an aerosol spray can of dry graphite lubricant on the input shaft instead of grease."