@Will he heck as like On my 1932 Lagonda the Hartford shock absorber pressure, according to the manual, should be set to 30 - 35 Lbs. With your method it is not possible to do that. I take the Hartfords off the car and press each down on scales. I tighten or loosen the nut until the scales reads 30 - 35 Lbs. I have used this method, as described in the original Hartford brochure, for 40 years now; it works perfectly and is accurate. However, it is a big job. I therefore do this only once (or every 10 years or so). When the adjusted Hartfords are back on the car I check the speed with which the jacked-up wheel comes down to the ground using your method. I note the time it takes for the wheels to come down from 30 cm (it differs for front and rear) and henceforth use those figures to adjust the Hartfords while they stay on the car.

No mention of fibre discs, these are polymer discs with zero stiction, easy to set up with a pull luggage type gauge.