Complex sentence: Some cars made up to about 1960 used left-hand and right-hand threaded lug nuts for different sides of the vehicle to prevent loosening, until it was realized that the taper seat performed the same function.
Split into simpler sentences: Some cars made prior to about 1960 used left-hand and right-hand screw thread for different sides of the vehicle to prevent loosening. It was later realized that the taper seat performed the same function.