The best clutch for your application isn’t always the lightest, the biggest or smallest, or the least or most expensive. There are a variety of factors that determine which clutch unit to choose. Be sure to take all of these into account before picking out your new clutch.
Lightweight applications can utilize lighter, smaller clutches, but they are more susceptible to heat build-up. Heavier clutches with more discs, on the other hand, are more durable and withstand more abuse from heat, but they have a higher moment of inertia. The key is to find the best balance for your application.
Moment of Inertia, or MOI, is a measurement of how much energy it takes to spin an object. The heavier or larger the object in diameter, the harder an object is to accelerate or decelerate. If two objects are the same weight and one is half the diameter of the other, then the smaller diameter object will accelerate and decelerate faster with less overall energy being used. This translates to a faster acceleration coming out of a turn, and a faster deceleration going into the next turn. Faster acceleration = speed advantage over the competition. Reducing MOI does not increase horsepower, but it does make horsepower more effective.
Check the Rulebooks!
Before you purchase any clutch system, always refer to your sanctioning body’s rulebook. Most sanctioning bodies indicate the minimum clutch diameter permitted for the friction/driven discs. Furthermore, some sanctioning bodies specify the number of discs allowed and the type of friction material, including metallic and carbon/carbon. Verify the clutch diameter, number of discs, flywheel or flexplate alloy and the minimum diameter of the friction/driven discs before purchasing a clutch system.
Now that you understand the importance of MOI, you might be inclined to choose the smallest diameter clutch available, but choosing the smallest assembly is not always best…
Smaller clutch = less radial friction surface = more heat and higher rate of wear.
If you drive a light clutch around the paddock area, you will be operating the engine at a low RPM, which will cause it to stall easily. You will rev higher and slip more while driving in the paddock, resulting in a higher rate of wear of the clutch components. If you don’t have a crew to help push, or a winch to get the car on the trailer, consider the best clutch setup for performance, reliability, durability and value.
The torque capacity for a clutch is the clutch’s highest ultimate torque rating, or the maximum torque that can be applied on a continual basis and still maintain a normally expected fatigue life. To size a peak-torque-capacity clutch to your application, multiply the engine’s peak torque by 1.25 and choose a clutch that has as much or more torque capacity. It is important to choose a clutch with more torque capacity than needed to avoid slippage.
Button Flywheel - Takes the place of a standard-type flywheel. Used for cover-mounted ring gear and flexplate applications, it results in a lighter assembly and lower MOI.
Clutch Cover - A cover which encases the clutch plates. Cover-Mounted Ring Gear - Mounted with clutch bolts. The starter drive gear engages the ring gear to crank the engine.
Friction Discs - Made of various types of friction material – come into contact with both the flywheel and the pressure plate to create the force required to turn the transmission.
Floater Plate - Acts as an intermediate driving plate between the clutch discs on multi-disc units.
Flywheel - When the clutch is pressed, the flywheel utilizes friction against the clutch plate to determine the amount of force that the clutch is capable of handling.
Gas Slots - Slots that provide additional cooling to the internal clutch components.
Housing - Connects engine to the transmission and houses the clutch assembly.
Pressure Plate - Uses spring pressure to press the clutch disc against the flywheel and allows it to transmit a driving force through the assembly.