A crew of two members can remove the lug nuts and replace the tire on a race car on average in about 4 seconds. Most Nascar crews usually want pit stops to be no longer than 12 seconds. A second more could be the difference between winning a losing a race.
It obviously depends on the crew and what the reason is for the tire change (blow out, tread being worn down, etc), but the average time would be approximately 20 seconds.
