This happened to me, too! I was in my first Honda Civic... Generation 1 !!! (1976). I was headed down the 57 freeway (So Cal) just after sunset with a big van about 3 car lengths ahead of me and one lane over to the right. Next thing I know, I see a shower of bright sparks and a disk growing from the center of the sparks. Seems the van wheel fell off, the sparks were from the brake drum and the disk was the wheel getting closer and closer to me! The wheel bounced just in front of my car, then it skipped completely over and bounced behind me.

It never touched me, but I often wonder what would have happened if I had been 1/4 second ahead or behind my actual position. Scary stuff, and it stays with you for years (at least 25; this happened in 1981!).