4Terrain Ultimate Cover Assemblies with the Patented* ER2 Groove Design features a unique groove pattern which is CNC machined on the friction face of the pressure plate.
This groove has been specifically designed to increase the Mean Effective Radius of the pressure plate and assist in heat removal. The increase in the Mean Effective Radius of the cover assembly gives a significant increase in torque capacity.
By adding the groove to the pressure plate, the inside radius of the friction face has effectively been increased. The first 8mm of the pressure plate has all but been removed and added to this, there is progressively less material removed as the radius increases. The net effect of this is to move the effective inside radius further out.
When comparing the Mean Effective Radius (Rm) of the ER2 version to the non ER2 version you can see the ER2 version is further out. This increases the torque capacity of the clutch. Torque capacity is directly related to Rm.