A shape changing from round to disc which paced us for several minutes before speeding away. No sound.

Me and my cousin were going to take a ride and see how many deer we could spot. We would do this once in a while in the evening. The location was east Sugargrove road just east of U.S. 31. we started down Sugargrove and I noticed a black ball about the size of a basketball which seemed to be hanging in the sky.  It was at about a 30 degree angle. As we gained speed the object stayed with us. As I watched, it began to change shape from a ball to a disc as if it were rotating.  It continued to pace us until we reached the Stop sign at Custer road. When we stopped, it resumed the ball shape and sped off to the north and was out of sight in just a second. It never made any sound. I didn't make any report at the time as I didn't want anyone to think we were crazy. Now that there is a place to report, I felt it was necessary. I have never seen the object again.
Date is approximate.  PD