Great since of motion! It is a shame the rest of the biker wasn't as "sharp" as the back tire, but I'm not subtracting from my vote because it doesn't really effect my overall perception....Well maybe it is the difference between a perfect 10 and 9....:)
Yeaaahh! A fun shot to look at. :) Nice capture. I like the sense of motion that the panned background adds to this. Would have been a tad stronger IMO if the focal point had been more on the rider than the back tire, but it's still fine (tricky to do I know). Overall, very nice. Best of luck to you in the challenge.