The weather was warm and dry when we returned to Circuit de Nevers for the afternoon track session. This is a flowing, very fast track with a thrilling, Parabolica-like bowl (T2) that leaves you on the edge of the tire for a long time. Compared to the Rosso, the Rosso II features a wider center rib and revised shoulders with a larger slick area and a stickier compound. We rode everything from a Ducati 848 to Honda CBR1000RR, but learned the most aboard Yamaha's R1. The muscular yet easy-to-manage Crossplane engine highlighted the exceptionally predictable behavior at the grip limit-spinning without sliding-that makes the Diablo Rosso II such a confidence-inspiring tire. And though it's advertised as a street tire, on-track durability impressed. A final, 25-lap endurance session on the rubber-munching BMW S1000RR revealed no appreciable grip degradation or excess wear.