I think most people associate the word "athlete" with the classic sports and what it takes to do them. Running, jumping, swimming, that sort of thing.

This is not to say a race car driver is not athletically inclined, though some of them look like they would die if they ever had to run a mile, but it can also be seen as sports PC to call drivers athletes. I think you would simply call them professional race car drivers, having all the attributes and qualifications that that entails.

I can't imagine anyone would really mind being called a pro race driver.