I liked them a lot, the first one is upside down though. I think if you used a narrower aperture like f8 - f11 you would get more of the rider and bike in focus without hurting your motion blur too much. Its funny how getting a pan of slower moving objects is sometimes harder than fash objects like cars.
You have done an excellent job to pan as smooth as you have, 50mm lenses dont offer much stability like a heavier 200mm.
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