The diaphragm has the highest clamp load with a full size disc and the step unless you go over center with the diaphragm. As the disc wears the pressure decreases and this is why the clutch slips when the disc wears out. Now if a clutch was designed to have a flat flywheel and full pressure with a new disc and you put a step in the flywheel, this would push the diaphragm over center and decrease pressure when first installed.....The issue with going over center is the pressure decreases extremely fast and the step could cause the pressure to be too little and the clutch to slip. Since the car came with a step flywheel most companies are designing aftermarket clutches to work correctly with the step. If a company was to make a clutch for the Z designed to not use a step they should state this with the install instructions as this would be an exception to the norm.
