The wheel appears to be disintegrating BEFORE he hits the manhole cover. Of course, there could have been another one a block back.

Years ago I encountered one on my bike where the cover had actually broken in half, and half of it was missing leaving a gaping hole. Of course, I didn't actually HIT it. I reported it to the utility company who reported it to the city, and the next time I passed it, it was in the process of being repaired.