I've ordered some aftermarket wheels, which I know the factory lugs aren't going to fit. Diameter of the head on the OEM bolts is too big. Knowing that I should purchase a set of longer bolts or convert to a wheel stud conversion kit.
In fact, I am going to order a set of stud conversion now because the bolts are becoming a pain to use without a pin.
I also did some study of them. There are several advantages:
1.They offer an easy way to align the wheel when mounting;
2.They allow for the safe use of different thickness wheel spacers;
3.It is compatible with both ball and conical seat lug nuts, which is suitable for most factory or aftermarket wheels.
(Quoted from:Wheel Stud Conversion for BMW
I am willing to buy a set of Titanium studs cause I learn that: "Titanium alloy materials, which possess high mechanical properties, not only have great fatigue strength and tensile strength performance but also maintain great strength at extreme temperatures up to 400 to 500°C. They are light in weight, also have extraordinary corrosion resistance."
P.S. These pics comes from Webs.