Went out to the hillclimb yesterday again. I had fun and was happy at how the photos came out on the cameras screen. When I got home though and put them on the computer the shots weren't sharp. A section of the car would be sharp enough but then either the front or rear of the car was blurry and not appealing. I got a few that were decent out of the 300 or so I took but I want a better hit rate. I got a better hit rate last time I went out (first time in years), I thought I would get more this time but I got alot less. I was using fairly high F/stops and shooting between 1/50 and 1/60. That created the amount of blur I wanted, any faster and it was freezing the motion too much. Also using AF continuous with 9 focus points. I found 21 would sometimes jump away from the car and focus on a tree etc. Is it just the reality of shooting with the low quality kit 18-55 lens? Would a better quality lens have a better success rate?
This is what I am talking about:


The rear of the car isn't perfect, but not bad, the front of the car however is not acceptable.
Thanks for any help.