Originally Posted by Ilia@IND
I wonder if it's shearing more from vibration than from actual constant load.
They're rubber-mounted, so I'd say that is extremely unlikely. It could happen, but only on a defective bolt IMO, not as a root cause by itself. I'd also rule out excessive torque, as you'd need a crapload more than normal to cause tensile failure on such a big a$$ bolt. Unfortunately, I don't expect posters to tell us the truth for fear of BMW/dealers reading this forum and denying warranty, so we have to take those posts with a grain of salt (understandable). Here are the most likely causes IMO:
- Owner abuse in the form of axle-hop, repeated launches, etc.
- Missing or loose bolts from an exhaust installation
- Bad aftermarket spring job, where installer uses diff/sub-frame as lever to remove/install springs.
- lifting and leaving car raised from the differential for long periods of time
- Road hazards, like big potholes, hitting a curb, etc.
- Defective bolts (very unlikely IMO).
Defective bolts are a possibility, but I could bet cash money there were at least one of the other factors mentioned above in each of those cases. But again, we'll never know here (unfortunately) for fear of self-incrimination. Checking one of the severed bolts would quickly put prove that theory or put it to rest. If defective, it'd be an immediate recall, and it's something quite cheap to fix, so I don't see BMW playing games with that.
I wouldn't consider this car unsafe Rac3rX. If you believe everything on the internet, you'd be paranoid by now
. Enjoy your car man. If you don't abuse your car, there's nothing to worry about IMO. Yes, I'll keep an eye on these threads, but am not concerned about this at all since I never abuse my car, and always drive it mostly alone. Good day.