Organic fiber type full-faced disc is developed for high heat resistance and matched to a clutch cover engineered to provide increased clamp load with minimal change to clutch pedal effort. Exedy is a supplier to many of the OEMs and is one of the few companies in the performance clutch market that engineers and builds their clutch covers (pressure plates) from scratch rather than re-working an existing OEM cover. This stage 1 clutch is ideal for street performance or mild motorsport applications requiring superior partial engagement performance and minimal drivetrain shock loading. Kit includes disc, cover, release bearing, pilot bearing, and alignment tool. Also available in an HD (Heavy Duty) version with further increased clamp load at the expense of noticeably heavier pedal effort compared to stock.
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What should be taken into consideration when selecting a clutch? First and foremost the clutch must be rated to handle the torque output of the engine. Clutch torque ratings are at the crankshaft. A clutch that is just marginally able to support the engine output will most likely have a shorter life expectancy due to the loss of holding power as the friction surface wears.
The second consideration is the type of use. Hard launches and severe clutch slippage as might be required in certain driving situations will lead to rapid increases in clutch temperatures that may destroy some types of friction materials. In these cases a high temperature friction material such as a sintered metallic, ceramic based, or carbon type may be required even if not required for the torque rating. More aggressive clutch materials and racing type clutch designs may suffer from severe shudder during partial engagement making them difficult to drive on the street in traffic.
What are the characteristics of the friction material in an Exedy Stage 1 clutch kit? Exedy "ultra fiber" type discs are used in their Stage 1 clutch kits. This is an asbestos-free organic friction material that retains a high coefficient of friction even under motorsport type conditions. It has a higher temperature range than an OEM disc and it maintains a stable wear rate over this wider temperature range. Additionally, if the disc heat range is exceeded it will recover from temperature fade conditions if allowed to cool down. Specifically, Exedy uses a a copper weave embedded in the friction material composite to increase the temperature resistance. Additionally, the burst strength of the disc is increased making it more suitable for a racing environment.
What is the "heavy duty" or "HD" version of the Exedy Stage 1 clutch kit? The standard Stage 1 clutch cover design provides increased clamping force without requiring significantly increased pedal effort. In most cases pedal effort is very similar to stock. However, the HD version kits have additionally increased clamping force at the expense of increased pedal effort. This needs to be taken into consideration when deciding if this type of clutch is appropriate for you. Addtionally, the heavy cover spring will increase stresses on the clutch fork and pedal components.
What is the difference between pull and push style clutches? The difference is the direction of movement of the pressure plate spring fingers in order to disengage the clutch. With a pull style clutch the release bearing is locked to the pressure plate fingers and the clutch fork pulls the release bearing in the direction of the transmission to disengage the clutch. A push style release bearing does not need to be locked to the fingers and is moved by the fork in the direction of the engine to disengage the clutch. A pull style clutch is considered to be slightly more efficient allowing the pedal effort to be reduced relative to the spring clamping force. However, the linkage is more complicated with a pull style clutch.
How do Exedy clutches compare to other aftermarket brands? Exedy is a large clutch manufacturer with extensive engineering and manufacturing history. They are an OEM supplier to Subaru and many other marques and able to engineer and build each clutch from scratch to suit the specific requirement. Many smaller aftermarket clutch brands often re-work OEM clutch covers rather than designing and building them from scratch. This may mean less than optimum pedal effort and poor clutch performance.
What installation procedures need to be followed for the best possible results? First of all the flywheel needs to be properly resurfaced when a new clutch is installed. Stepped flywheel designs need to have an equal material depth removed from both the friction surface and clutch cover mounting surface. The friction surfaces of the flywheel and clutch cover (pressure plate) should be thoroughly cleaned with solvent to remove any rust preventative. The transmission input shaft splines should be lightly greased using the supplied lubricant. The clutch disc should be test fitted to the input shaft splines to ensure free movement on the splines and to remove any excess grease (wipe the excess from the clutch disc hub). The clutch disc should be accurately centered using the supplied tool. The clutch cover should fit snugly on the flywheel dowels and the bolts should be tightened progressively and evenly to the factory torque specification. The release bearing should spin smoothly and without noise. The contact points of the clutch fork should be lubricated with a high temperature grease. In some cases it may be necessary to adjust the pedal linkage after installing the new clutch so that the pedal engagement point is correct and that there is proper free play as per the factory service manual.
What is the break-in procedure for the clutch? Clutch break-in is required to ensure that the friction surfaces wear in so they are in full contact across the entire surface area prior to applying heavy engine power. During the first 300 to 400 miles drive the car normally in stop and go situations avoiding launching the car hard or at rpms above 3000. Avoid heavy power applications or excessive clutch slippage during this time.
