Why are side mirrors glass instead of plastic? As far as I can tell they are just glass with a layer of reflective material adhered to the surface, would plastic not be a better alternative as it would not shatter if it fell out.

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    Welcome to the site. Why would the glass fall out in the first place? They are captured within the sideviews. They use glass because glass is very hard and can stand to be cleaned very often, which plastic wears out in a short period of time in relative terms (plastic scratches easily in comparison). Aug 19, 2017 at 12:34
  • @Pᴀᴜʟsᴛᴇʀ2 Thanks, I asked because mine was recently knocked out by a truck driving past me, it just occurred to me that a treated plastic may have a better time surviving the impact. Although I take your point about glass being far more resistive to cleaning and wear. Aug 19, 2017 at 12:41
  • If it fell out due to a truck going past, there was an issue with it in the first place. It's just something you don't regularly see. I've replaced a couple of side view mirrors and they are really a PITB to get done (taking out more than putting back). Aug 19, 2017 at 12:46
  • @Pᴀᴜʟsᴛᴇʀ2 Apologies I should have been more clear in my initial explanation the truck hit the wing-mirror causing the glass to fall out and smash Aug 19, 2017 at 12:48
  • No apologies needed ... physical contact causes all kinds of bad things to happen! Aug 19, 2017 at 13:00

1 Answer 1


The first and simplest reason is that glass is cheap cf. a plastic that will support the uv rays that will hit the mirror during use. Then, the glass is designed to shatter into small pieces when it gets broken not forming shards which are more likely to cause injury.

Some cars have plastic headlights and we now have to buy products to reduce the discolouration due to aging....

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