There are many different mirrors on the modern automobile that serve many different purposes. For the sake of simplicity, we'll discuss in length the three main mirrors—the passenger side mirror, drivers' side mirror, and rear view mirror—as well as the details to buying, replacing, and finding the proper type of mirror. It is important to remember that each mirror is different, and each type serves a different function and makes use of a different type of glass.
Drivers' Side Mirror
The drivers' side car mirror is a very basic optical mirror intended to provide drivers with an easy side view of the cars behind and to the side of their car. The mirror is neither convex, nor concave, and is generally very accurate as far as relating the distance and size of cars in the mirror and their current distance to the automobile.
Replacing this mirror is easily accomplished, and requires no specific glass, but does require some level of detail and tender care. Removing the mirror from the mirror assembly can be done with a small amount of heat capable of liquefying the adhesive. Once heated, the mirror can be removed by sliding it in one direction until there is enough of an edge to take firm hold and remove with the force of your hand.
Passengers' Side Mirror
On the passenger-side of the automobile is a very different kind of optical mirror: a convex mirror. In the United States, convex mirrors include the verbiage “Objects in mirror are closer than they appear.” This warning is to notify the driver and passenger that because the mirror is convex, there is serious distortion in the size and perceived distance of objects behind the car.
A benefit, though, is that convex mirrors give a very broad line of sight that when combined with the distance and angle between the driver and mirror gives a very clear view of what is behind the car at all angles.
Like the drivers' side mirror, this mirror is equally easy to replace. However, take into consideration the degree of convexity as it is different from one car to another. Most auto glass dealers sell car mirrors that are made to fit your specific make or model, whether it be a Ford Focus, Toyota Camry, or a ten-foot tall Dodge Ram pick-up truck.
Note: Both Passengers' side and drivers' side mirrors can be enhanced with a small button mirror known as a “blind-spot mirror.” These mirrors are generally very convex in shape, and allow for a driver to immediately review his or her blind spot without turning around. These mirrors can be had for only a few dollars online.
Rear View Mirror
Unlike the driver and passenger mirrors, the rear view mirror is usually a part of a greater assembly, and cannot be replaced by simply changing the glass. Most car owners will eventually experience a problem with their rear view mirror that is purely a matter of design—they fall off constantly.
While this can be a bit of an annoyance, this feature was actually desired as a way to keep the car safer during collision. Due to the design of a rear view mirror assembly, the mirror is very broad but the base is very small. If the mirror were to be struck, the thin base could easily shatter the windshield as all the force gets transferred from 8-10 inches of mirror to a small mount usually 2x2” or even smaller.
Previously, the mirror was secured to the dashboard. While this meant less likelihood of glass breakage, it did obscure the line of sight, and was determined to be a safety hazard in an automobile accident. As you can imagine, hitting your head on a metal mirror wouldn’t be at all comfortable.
There are two primary types of rear view mirrors: prismatic mirrors and dimming mirrors. The prismatic mirror is the most simple, and is intended to be tilted at different angles to reduce reflection of headlights in the eyes of the driver. Usually, a small tab is found at the bottom of the assembly which can be pushed back and forth for adjustment. Automatic dimming mirrors are more common in sedans and luxury automobiles. Using sensors to detect light, these mirrors instantly deaden reflection. As the light fades, or disappears, the sensors allow for more reflection and better visibility.
Which type of mirror to use is up to the discretion of the driver. Those with smaller compact cars may prefer a dimming mirror, since it is likely that the headlights of other drivers will shine directly into the car. Taller cars would be just fine with a simple, non-dimming mirror, as it is unlikely that ever taller cars will be immediately behind them to shine their headlights into the car.
Mirrors with additional features, such as a mile per gallon rating or temperature gauge can usually be replaced at a dealer lot or certified auto garage without replacing the full assembly. However, these types of mirrors usually require more expensive OEM glass so as to be replaced with glass that fits the assembly correctly.