The flywheel’s role in a vehicle is to do the following;
Because the flywheel is bolted directly to the crank, the flywheel will always spin at the same rate as the crank shaft of the engine. Around the outside of the flywheel you will find a ring gear. Although it is part of the flywheel, ring gears have nothing to do with the clutch itself. They work with the starter motor.
Grinding or replacing a flywheel
When a new clutch kit is installed the flywheel must be either replaced or ground. This is because excessive heat from normal driving changes the structure of your flywheel surface which creates less friction affecting the performance of your clutch. If this is not done common issues experienced are shudder and or slipping after installing the new clutch kit.
Why grind when you can replace?
There are three main technical reasons to replace a conventional flywheel instead of grinding it.
Dual Mass Flywheels
Dual Mass Flywheels were introduced to dampen driveline vibration and noise more effectively. The need for this escalated due to increased torque in modern engines (especially diesel engines) and consumers expectations of noise and vibration.
A Dual Mass Flywheel (DMF) is comprised of two flywheels that work together with dampening springs or planetary gears to reduce noise and vibrations.
As the driveline dampening occurs in the flywheel most DMF clutch discs do not contain springs but are generally cushioned to give smooth engagement.
Although DMF’s are very effective at dampening driveline noise and vibration they have 4 major downfalls.
Dual Mass Flywheel Replacements/Conversions
Dual Mass Flywheel Replacements (DMR) move the damping system from the flywheel to the clutch disc/plate. This returns the flywheel back to a conventional solid mass flywheel and the driveline dampening to the clutch disc.
To effectively dampen driveline noise and vibrations a multi rate (MR) clutch disc is used in DMF conversion kits (DMR). This MR clutch disc uses a torsional damper with separated first and second stage dampers. The dampener is tuned for low torque low angularity dampening as well has high toque, high angularity dampening.
Advantages Over a DMF
Note: as dual mass replacement/conversion (DMR) clutch kits do not as effectively dampen driveline noise or vibration an increased vibration and noise might be detectable especially at low RPMs. However, this will not damage the vehicle’s driveline.