The 1991 Ford Mustang Base 2.3L 4cyl bolt pattern is 4-108 mm. This means there are 4 lugs and the diameter of the circle that the lugs make up measures 108 mm or 4.25 inches across. To get a close measurement of your 4 lug bolt pattern without a bolt pattern tool you should measure from the center of one lug to the center of the lug across from it.
