Crazy. I am reading a book which has this exact topic in it:
Providing ready compensation for different weights of rider and the added weight of a pillion passenger has always bedevilled the design of rear springing for roadsters because the load on the springs may easily be increased by 50 or even 100 per cent. Under conditions of varying load, multi-rate springing, however achieved, may be an advantage. The most common traditional solution to the problem has been to provide a stepped cam adjustment for the preload on the springs. By this means the attitude of the machine can be preserved for different loads and full travel retained. But no single spring rate can be satisfactory, in any case, only BMW and MZ provided a built-in hand adjustment for the pre-load and few riders bothered to use the C-spanner otherwise necessary.
A much better form of compensation was that designed by Phil Irving for Velocette. In this, the top anchorage for the struts was slotted so that their inclination could be varied to suit the load by slackening two handwheels. Thus both the effective spring rate and the damping, measured at the wheel spindle, were adjustable, but in later production versions a spanner was required and so the adjustment was used less than it deserved to be. A consequence of this scheme is that less wheel movement is available on the hard setting than the soft. A later solution to this problem was the Boge Nivomat self- levelling strut first offered on BMW roadsters in the early 1970s.