I prefer this ones to the other bunch Steve. I wonder if a slower shutter speed might not have captured some speed? Easy for me to comment sitting on the other side of a DSL line :-)
I’ve read that somewhere around 1/125 will give a nice speed for panning in motor sports. I’ve only tried this once at a Motocross event on the 100-400 and it worked out “OK”. Don’t know how it’d work on tarmac racing.