I would have to search to find the exact mechanical reasoning, and data to prove why bolts holding wheels are stronger. The germans did this for the Porsche, and Volkswagen autos. I am friends with several technicians who work at the Audi/Volkswagen dealer near me and the said that in their factory tech training classes, it is stated still by the factory trainers that bolts have more holding power than just studs. I believe that the two studs are helpful, but not necessary for getting the wheel up and onto it's "perch". Two is plenty, and the other four are bolts. My New Holland TC48DA has all 6 bolts on the front axle. Seems abit of a reach to believe bolts over studs are stronger, but I've seen it, and heard of it from two sources now. Would be an interesting web search. You would think they are just being cheap by using bolts.