Impossible to know for sure the truth but it seems that it was hard for those Porsche to find a proper balance between the very stiff suspension set-up they have and the tires.
@ MATADOR for your "eyes only". When we say each detail counts, knowing that the Porsche is supposed to have the best air-co system it seems that not all drivers will agree:
https://www.youtube.com/watch?v=uNlgq65gCGA
Then to 2'15" After that, Roger unperturbed but not too happy…
