Here is the results of shooting at the settings mentioned.
_MG_9319 by CvsN2013, on Flickr
_MG_0752 by CvsN2013, on Flickr
_MG_9292 by CvsN2013, on Flickr
You can see that in the first two f7.1 is just not enough when you look at the rear wheels they have a bit of distortion. Time to get to the track and try this out on racecars!
~Kev