[Suberman]

Originally Posted by Admiral Ballsy

By the way, is there any verification/documentation of the proposition that the mirror mounts the way it does for regulatory reasons?

The notion makes sense, but there are five cars in my household - all 2012 or 2013 - and only two of them have mirrors that mount like this - the other three have the old-style shoe-glued-to-glass setup. Seems as though if it really was a regulatory requirement, they'd all be the same or similar.

I found this - http://www.nhtsa.gov/DOT/NHTSA/Vehic...TP-111-V00.pdf

Pertinent text seems to be:

(1) REQUIREMENTS (S5.1.2)

If the mirror is in the head impact area, the mounting shall deflect, collapse, or break away without leaving sharp edges when the reflective surface of the mirror is subjected to a force of 400 N (90 lb) in any forward direction that is not more than 45 degrees from the longitudinal direction.

So it seems as though breakaway is an option but not a requirement - collapse works too, and that seems to be how most cars are made; the link connecting the base to the mirror pivots downward and allows the assembly to collapse toward the glass.

Most manufacturers use a spring clip that deforms to allow the mirror assembly to depart its mounting. Same idea as a ski binding. Some may elect to go the deformation route but spring loaded detachment is preferred.