The 1991 Mercury Cougar Base Model bolt pattern is 5-108 mm. This means there are 5 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 5 lug bolt pattern without a bolt pattern tool you should measure from the center of one lug to the outer edge of the lug furthest from it.
