As tires evolve, chassis must evolve. When Michelin brought a big new rear tire in 2006, it set every chassis to chattering. The usual emergency fixes (like lead-filled axles to tune out certain flex frequencies) worked for Honda but not for Yamaha. Valentino Rossi was stopped by chatter for four races, and only reverting to the 2005 chassis enabled recovery. Chatter, stability, chassis flex, and engine characteristics are mysteriously entangled. There is no textbook. The ’06 championship was lost.