Can only be used with 16", 16.5”, and 17.5" wheels on an 8 on 6.50" bolt circle. Axle overhang requirement: Leaf spring straight axle = 8.25" per side. Leaf spring drop axle = 9.00" per side Torflex axle = 9.00" per side. A retrofit application will not affect the current axle outside of tire dimension. This disc brake system will not retrofit Dexter 4” drop spindle axles manufactured prior to January, 2003.**TT