Do you have an ABS light? Start the car and see if the ABS light comes on. Or, look for a hall effect sensor (little plastc plug) next to a toothed ring on the axle, right behind the rotors.

-Philip Maynard '95 Contour [71 STS | Track Whore] '97 Miata [71 ES | Boulevard Pimp] 2006 autocross results