looks to be about 200 mi:
WHERE IS WILLOW SPRINGS INTERNATIONAL RACEWAY?
WSIR is located approx. 90 miles North of downtown Los Angeles, California. WSIR is on the north side of the "Antelope Valley" area, in southeast Kern County. WSIR is physically located at 3500 75th Street West and Rosamond Blvd. in Rosamond, CA. - just 6 miles from Highway 14 and with easy freeway access!
from
http://www.mtctrackday.com/course.shtml
mapquest directions, sd to rosamond