The conical lug's taper is normally 60 degrees (although 45 degrees is common for wheels designed for racing applications), and is designed to help center the wheel accurately on the axle, and to reduce the tendency for the nut to loosen due to fretting induced precession, as the car is driven.
The conical lug's taper is typically 60 degrees (although 45 degrees is common for racing wheels), and is designed to accurately center the wheel on the axle, and to reduce the likelihood of the nut loosening due to fretting-induced precession as the car travels.