I'm experimenting a lot lately with slooow shutter speeds and often get some great results panning at possibly 30th or 60th sec, difficult at times at the speeds they go.
This is a chicane used just to slow them at the end of a VERY fast straight so it is a chance to get one head on, bikes are good thro here.!
I was pulling the focus barrel back from 400 to 100 during the exposure.
That's a large lake behind with lots of geese, but couldn't get close as it is out of bounds when these things are whizzing round, even on a practice day like today.