Left side tire
Did the install and it went off without a hitch except for a few minor things. My feb 08 E90 had the hood switch cable out and affixed to the side of the tray. I didnt need to remove the break pump cover. Also, the "left rear wheel" is the driver side wheel (in left hand drive, e.g. N American, cars). Getting the wheel off was the hardest part, but a 25 dollar breaker bar fixed that without breaking a sweat. Now it lives in my trunk should I ever need it. Clown nose was blinking as soon as I plugged the battery in and the siren went off when I waived my arm through an open window. Success!