I agree Nick, the more the more I think about it the less I'm willing to take any chances driving on it. I'll swap out the wheel for a winter wheel until I know what's going on.

hayaku: I don't think the bolt(s) sheared. It looks like a tensile break as it has a slight spiral appearance. I checked the tire pressure as you suggested and it's ok.

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Wake up every day that would be a start.