The 1998 Ford Expedition Eddie Bauer 4wd bolt pattern is 5-135 mm. This means there are 5 lugs and the diameter of the circle that the lugs make up measures 135 mm or 5.3 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.
