Hi Debra,
Indeed you have, thanks.
Across the series; your exposures are very good, I'm sure this must have been a combination of in camera and PP, particularly the latter to allow us to see detail in the rider's faces.
WB is also good throughout, but with a white reference in every shot, I'd be disappointed if they were not
I couldn't extract any EXIF data, so I have no idea what shutter speed, aperture and iso you were using.
Probably the two most significant issues I see (and I am being super-critical to explore something that might be useful for you) are noise in the shadows and motion blur, plus perhaps even camera shake in some. This makes me wonder, after the polariser (or ND), what these ended up at? Could you advise for #6 please?
Obviously you are at the mercy of the backgrounds that are at the venue and although these are bright, at least they are neutral, they could have been much worse.
Shot timings all look OK on these, it pays to have some variability, if they were all exactly the same, it would be a very boring series.
Cheers, Dave