Sudrad was one of three wheel makers that supplied Porsche up until the late 50s. Starting in 1960 only KPZ and Lemmerz supplied the wheels, but I am not sure why. While Sudrad did supply a fair amount of 16" wheels they did not supply that many 15" wheels that were on the cars starting in late 1955. I say this because I build sets of wheels and see far fewer Sudard's than I do Lemmerz or KPZ, in fact I generally avoid buying Sudrad because it is so hard to build sets, they are that rare. So for whatever reason they slowed than eventually stopped supplying wheels to Porsche, whether it was Porsche's decision or Sudrad's I don't know.
– Adam Wright