BMW rearview mirror fell off..

You mean BMW did not over engineer the rearview mirror? That's not like BMW at all. I would go to parts store and buy the glue for that purpose. It will probably stick right back on. If you can separate the mirror from the base tab glue tab first then once secure slide the mirror back on. The mirrors usually have a one way tab to bend then the mirror slide off the base.

 

Looking at the photo on a proper computer, I wonder if it was some adhesive they used that failed in an odd way after too many hot/cold cycles on the windshield. It looks relatively clean ala no cracks/spider webbing of the laminate. As such I agree....if it can 'slot' back together (aka no lost shards/etc), then a strong glass-plastic outdoor level adhesive should do the trick.

 

Had this happen on a Chrysler 300 where a chunk of the inner glass layer broke away from the windshield and stuck to the mirror mounting button. We glued the glass and button back into the glass matching the pattern of breakage with epoxy. It worked for awhile then failed again as expected. The summer heat weakens the epoxy. Eventually replaced the windshield and reattached a new button and had safelight do the entire replacement button. etc. You might be able to get away for awhile by gluing the glass/button assy. back together with some of the super adhesives avail, but eventually it will probably fail until the windshield is replaced.

 

If it were me.. I would use some type of glass glue on the middle part and 3M VHB tape around that circle area.

I'll tell you this. I've used Mr. Sticky glue and it is extremely strong.

Ray

 

If the glass had a chunk break off like that I'd be more concerned about the strength of the glass if something from outside while driving hits it. I would probably just get new glass for safety rather than try to patch that back up. From the dash it looks like maybe an E39 M5? If so, definitely a car worth putting new glass in rather than say a regular 528i that will be scrapped sooner rather than later vs M5 that is to last as long as possible. Edit: E46 M3 I see in profile and I see now based on the trim it matches.