Not to dampen the engineering debate, but all of this is somewhat missing the point - the screw in stud has inherent flaws, 10.9 or 12.9. The frequent use of these type of studs amazes me, given their failure rate - I know it makes for an easier wheel swap, but not worth the risk (I can take the extra 2 minutes to use screw-in guide studs for mounting wheels - I'm not timing my pit stops). If you are going to run these, please remember they are race parts, with a rather short duty cycle before replacement (ask the BMW.
It also sidesteps the fact that there are limitations to effective clamping force that are far more problematic than the ultimate fastener strength (a bolt tht isn't properly torqued is already half broken, and there are a host of issues that compromise the effectiveness of torquing lugs).
CORE motorsports has some good discussion, and they are good with Q&A for you techhies. If I get any more serious about tracking, I'm going to have them make me a set of hubs (about 650-700/hub, IIRC). I believe CORE sells 12.9 studs (ARP or MSI) with these kits, and matching nuts.
https://www.core4motorsports.com/tech
Here is an excerpt from my communications with them:
From and engineering stand point, going to a grade 12.9 for a wheel bolt isn't justified. Need to keep in mind the material you're screwing into (hub), which is typically far from the strength of a grade 12.9 fastener. It's the equivalent of using mis-matched screws and nuts. If (and that's a big if) a grade 12.9 bolt is to be tightened to the level that they should theoretically be tightened to, there's an increased risk of deforming the threads in the hub, or worse, stripping them since the capacity of the bolt is much greater.
So in essence, the benefit of a grade 12.9 fastener is the ability to be able to clamp the parts more tightly. If that can't be done, what's the point? Answer: there is none. This is where there's another advantage of a press-in style stud since you don't rely on the hub material to generate clamping/tension if you want to move to a higher grade fastener. You just get the correct grade lug nuts.
My first recommendation would be to stick to the OEM wheel bolt or equivalent grade 10.9 and just make sure you keep track of the cone seat of the bolt to be sure that no galling is occurring from the aluminum wheel to the lug nut.
My next recommendation would be to use a wheel bolt that has a floating conical washer, like these:
https://www.bimmerworld.com/Wheels-T...3-X5-19mm.html
In my torque/tension testing, I found this floating-washer style not only gets the clamping closer to the ideal value, it does so very consistently after many tightening/loosening cycles because it prevents aluminum from the wheel galling onto the cone set of the bolt/nut. You will see many OEM vehicles and trucks starting from early 2000's onward that have this floating style concept. There's a reason for it. If you haven't read our tech pages which goes more into galling, etc. see here:
https://www.core4motorsports.com/tech