The 1983 Oldsmobile Firenza Base Model bolt pattern is 5-100 mm. This means there are 5 lugs and the diameter of the circle that the lugs make up measures 100 mm or 3.94 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.
