race driver vs racer

race driver and racer both are nouns.

Word	Noun	Adjective	Verb	Adverb
race driver	Yes	No	No	No
racer	Yes	No	No	No

As nouns, race driver and racer are synonyms defined as:

Other synonyms of race driver include automobile driver.

race driver (noun)	racer (noun)
someone who drives racing cars at high speeds	an animal that races
	slender fast-moving North American snakes
	a fast car that competes in races
	someone who drives racing cars at high speeds