Sounds like you should investigate fixing/changing how the spare is mounted.On my 2018 320S, I added a spare tire mount to the Jack Post. It is solid and tire also rests on the trailer frame. (View Post)
No direct experience with timed electric brakes BUT have driven surge brakes. What you describe sounds about the same as surge brakes - - - which I dislike. Believe you would be far more comfortable … (View Post)