I looked at a picture I had of the Roin wheel. your stud is sticking out 1/2" from WHERE on the wheel. The outer surface, the inner cone area? I assume you mean the outer surface. If yes, then you have more stud down inside the cone taper. I would not use studs with a shank as shown. Get a stud that has the correct taper angle and if I believe it will be fine. You will have way more than 1/2" of thread engagement. Send a picture of the wheel on the car.
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