TOWCESTER, England—Pirelli Motorsports' pitch to the Formula 1 community to consider changing the sport's tire spec to an 18-inch rim potentially would carry with it an unsprung weight penalty of nearly nine pounds per tire/wheel assembly.
The additional weight would be in the mass of the larger wheel, Pirelli said, which would add about 4 kilograms—or 8.8 pounds—per wheel, based on current wheel design and manufacturing. The larger diameter tire weighs about the same as the 13-inch rim version, according to Pirelli, because of the shorter sidewall.
Lotus F1 Team reserve driver Charles Pic gave the new design its debut July 9 at Silverstone Circuit, running 14 laps early in the morning in the 2014 Lotus E22 equipped with the 18-inch concept tires.
The concept tire was designed principally to showcase aesthetics rather than performance, Pirelli said, so lap times were not the focus. Instead, the objective was to gauge reaction to the very different new design.
“In our view, the new tires looked stunning fitted to the Lotus, and the reaction has already been felt all over the world,” said Pirelli's motorsport director Paul Hembery.
The tires were mounted on 18-inch wheels from O.Z. S.p.A., which is the wheel supplier to Lotus and three other Formula 1 teams—Scuderia Ferrari, Infiniti Red Bull Racing and Caterham F1 Team.
O.Z. did not comment on the wheels or the testing.
Mr. Hembery stressed that the tires tested at Silverstone Circuit are prototypes, “but if the teams decided that they wanted us to proceed in this direction, we have the capability to carry on development in this area and come up with a production-ready version in a comparatively short space of time.”
The 18-inch demonstration run came amid three days of mid-season tire testing at Silverstone following the July 6 British Grand Prix.
The tires tested have the same width as the current 13-inch tires (245mm at the front and 325mm at the rear) but a diameter that is 30mm larger.