“The Italian tyre manufacturer was established in 1872. Without clear corporate guidelines on how to use the logo, it appeared in many variations according to what was popular at the time; the logos shown here represent only a small selection.”
Vintage Pirelli ad from 1922, via Pictorial Gems.
“The elongated P with its clever shift from thick to thin and back was a highly evocative way to portray the elasticity of Pirelli’s premium products.”
Update: 15 July 2013
I was contacted by Salvatore Gregorietti — designer of the latest iteration of the Pirelli logo. He said the information on the Pirelli website is incorrect, and sent me two correct designs to add to the evolution series above (1945 and 1970s). At the time of the latest design, Salvatore was partner at Unimark International with Massimo Vignelli and Bob Noorda.
More on the Pirelli website.
Pentagram’s Angus Hyland commented on the Pirelli logo in this archived post.
Pirelli signage photo (top) via F1Network.net.