The flywheel and pressure plate can be balanced on an arbor or with the rotating assembly. I prefer doing them with the crankshaft as any runout that is on the flywheel flange at the crankshaft can be compensated for in the balance. The flywheel is first brought to zero specs and then the pressure plate is installed on the flywheel and then this sub-assembly is then brought back to zero again but by working on the pressure plate. This way the flywheel is still at zero balance. If balancing the flywheel and pressure plate on an arbor, then the same routine. First balance the flywheel and then install the pressure plate and balance it. In either case, the pressure plate is marked so it can be reinstalled in the same balanced position on the flywheel when reinstalling in the vehicle.
Two reasons to balance the pressure plates. First being the tolerance of the balance whenever originally balanced and second, the pressure plate holes in the flywheel are not always perfectly centered which will automatically make the pressure plate ‘lopsided’ on the flywheel. Balancing the pressure plate on the flywheel automatically corrects for these situations.
The clutch disk is balanced separately on an arbor as it spins independently of the rotating assembly. After balancing a multitude of these components, I can confidently say that balancing is definitely needed in a majority of the cases.
If needing to balance a pressure plate later down the road, all that’s needed is the flywheel so you have a matching assembly when going back on the vehicle.
Lorena, Texas (South of Waco)