i'm on my fourth set of tires on my '04kgt, and am puzzled about something. i've had z4, diablo, z6 and now pilot II on my rear and to look at the tires, they don't seem to have any tread in the center of the tire. the design is purty, and flows from the side of the tire toward the middle, but only the end even crosses the middle of the tire. when the tire is on the road, only the tread fingers cross the center of the tire, and it looks effectively like like i'm riding on bare rubber. more tread, obviously, on the sides, but i'm talking about straight up riding. anybody got an explanation?