My rear view mirror just fell off the winshield..

Whats the best glue to use and will it hold it instantly?

a double sided adhesive pad hold the mirror on. they are still avaliable.

from flaps as well.

like a 3m double sided tape?

I use the factory part. I've tried the glue from FLAPS and the factory sticky pad is the way to go for sure. Clean the glass and the mirror with alcohol first and let dry.

No - it's more like a double sided foam tape which is designed to break away in an accident. Over time in the sun the adhesive dries out. Porsche dealers & the rest of the usual suspects sell them cut to the specific outline of the 914/911/912 mirrors' base, or you can trim the FLAPS type to fit without overhang.

Not a biggie & sticks instantly after you apply some pressure to seat it. Buy 2 for the next time.

... especially the cleaning 1st.

IIRC 3M may make the factory part.

its actually trim tape from flaps. the stuff works really well.

i used the little kit from FLAPS. it was some type of super glue like liquid adhesive and came with alcohol wipes for cleaning. fortunately, there was enough of an outline on the window to help me keep it in the correct spot. worked like a charm!

How about 2 stock adhesive ones stuck together, one on the mirror and the other on the glass, sounds wierd but my friend with his 356 tried this and it worked alright and its been about one year or so and the mirror is still on...he used 2 stock adhesive pads....