I have the 20" and love the Michelins. Keep them at full inflation. They are not as firm as the 21's I have experienced on loaner GTs, but strike a nice balance between the 19" and 21" for handling, I have had 20" and 21" Pirellis on previous sports sedans and suffered tire bubbles and failures multiple times... Glad that Bobby's roads in San Diego have been good to him and his 21" wheels, but our streets in L.A. are riddled with pot holes and they take their toll on Pirellis....