Edit: whoops, I thought this was dogbone's thread.
ryanosiecki, let me know if you want me to delete if it's too much of a tangent.
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ryanosiecki , In an effort to save some time and not write too much in this thread, I've gone into some detail about thread-in studs and why they're more prone to failure in this thread here (goes over some thermal effects also):
https://www.m3post.com/forums/showthread.php?t=1690683
And they most certainly are more prone to failure, as much as people may want to deny that they aren't. They literally have a fundamental design flaw for fasteners that undergo the varied loads that wheels studs do. There's even a 14mm thread-in failure from a Porsche that I shared in there as well.
dogbone, I know we've talked about this on the phone a few months ago, but I figured I'd ramble in here also. Let me know if you want me to delete.
So clamping force is the single most important parameter in a bolted joint, especially one that sees many directions of force application like a wheel joint. People tend to think that the studs themselves is what is taking most of the load being transmitted through the tire to the hub, then suspension etc.
In the case of braking forces, engine torque, and corner weight forces, it is the frictional force at the interface of the components that are being clamped by the stud that resists what are shear & bending forces (forces acting perpendicular to the studs). We all know basic friction physics; the higher the normal force/force acting perpendicular to the surface that an object rests on, the more frictional force you get. This phenomenon of frictional force in a bolted joint is the working foundation of structural bolts that keep buildings and bridges from falling down.
A stud/bolt size is chosen based on its clamping capability to resist tension forces (lateral load when turning in the case of cars) and to create sufficient frictional forces to resist shear forces. As soon as the friction interface is overcome/slips due to external forces, the studs take on all the perpendicular forces directly. When this happens, thread-in studs will and do go bye-bye much more rapidly than a press-in stud. And no one can deny that they are far more prone to failure. The frequency of this topic only persists in BMW and Porsche communities. Does anyone truly believe that people with cars that use press-in studs from the factory are doing anything different?
So the frictional interface of the components being clamped does resist most of the perpendicular loads (90+% when tightened correctly), but some portion of it still does go through the stud even if there's no slipping of the clamped components. And this portion increases as clamping force decreases to the point when it's 100% if the friction interface is overcome. That means that they are always undergoing some form of cyclical bending stress, and thread-in studs are inherently flawed to handle bending stress. And no brand thread-in stud is impervious to this, including MSI, which you can see 4 of nicely broken from an E9x M3
here on my website. ARP doesn't make thread-in studs (surprise?), so no documented cases of them
I'm pretty confident that super high strength 12mm press-in studs from ARP and MSI when tightened to what they're capable of, are sufficient. A Nissan GTR uses 12mm press-in studs. STi's and EVO's use 12mm press-in studs. All corvettes up until the new C8 use 12mm press-in studs. Ford was using 1/2" studs on their Mustangs until the latest generation.
Porsches only track variant model that isn't a centerlock moved to 14mm press-ins (Cayman GT4). All Porsches pre 996 generation were 14mm press-in studs before their move to bolts, which by the way, are more robust than thread-in studs.
What the 14mm buys you is some margin to handle bending stress as well as provides increased clamping capacity. What I question based on my testing is if people actually are achieving the extra clamping that 14mm can provide. My intuition is that most probably aren't to the level that they think they are.
As for changing press-in studs on the rear, it can be done with the hub still on the car with shorter length studs. Also, I'm fairly certain that you can remove the parking brake shoes and such without pulling the hub off. If BMW engineers overlooked servicing of the parking brake without taking the hub off, they should be executed
Sending you an email shortly on the 14mm press-in stuff.