A race car’s windshield is much different than the windshield in your daily driver. These machines are meant for one thing- to go fast. And to go fast, saving every ounce of weight possible is important. Because of this, race cars don’t actually use glass windshields. Instead they usually utilize polycarbonate- a synthetic resin material which can cut weight by more than half.
Polycarbonate is similar to plastic in that it is strong, but somewhat soft. It is the same material used to create bullet-resistant glass (which is actually polycarbonate sandwiched between glass) and fighter jet windshields. Polycarbonate is much more resistant to cracking from impact (from which race cars suffer regularly) than glass windshields and can take the abuse of white-knuckled laps around a track. The downside to this is that it marks much more easily.
Road debris like rocks and other objects can create gouges, pits, and scratches in the windshield. Therefore, many track use cars, like those used in NASCARⓇ, have thin clear sheets of film over the windshield that protect the polycarbonate from damage. These films can be removed and replaced easily when they lose clarity. In long races, several layers of film may be applied. This allows pit crews to quickly remove the top layer during maintenance stops and restore visibility for the driver.
For those trying to save every ounce possible, the windshield isn’t the only piece of glass that can be replaced. The rear windshield, side windows, and even quarter windows can be replaced with polycarbonate too. Hot Rod Magazine claims that swapping just the side windows and quarter glass saved them about 50 pounds on their Dodge Demon build project. Keep in mind that polycarbonate windshields are not street-legal in the US and are made for off-road use only. Always check with local, state and federal laws before making modifications.
Not going for an all-out track car? Other options may be on the horizon for high performance street machines like the light, but extremely tough Corning Gorilla Glass® windshield. Currently, has only been made available for the 2017 Ford GT, but this may change in the future.
If polycarbonate is cheap, saves weight, and can be easily replaced, you may be wondering why it isn’t used in everyday vehicles. There are several reasons. For starters, it doesn’t provide the same level of undistorted visibility, especially over time. Looking through a polycarbonate versus glass windshield can be equated to wearing a cheap pair of plastic-lensed sunglasses versus a pair with quality polarized lenses- the difference is clear. And have you ever seen foggy yellowed headlights on a car? Headlight lenses are made from polycarbonate also, and that’s what can happen over time from daily road use.
Secondly, polycarbonate is less “forgiving” thank glass. The added strength of polycarbonate is not always a good thing. For example, in the event of a crash, if the occupant were to come unbelted and collide with the windshield, instead of the windshield breaking and the energy dissipating as with a glass windshield, the energy would instead be absorbed through the occupant’s body. Therefore, the chance for critical injury may be higher with polycarbonate windshields.
The installation process is a bit different for polycarbonate as well. Instead of the windshield being “glued” to the car with a urethane for glass windshield installations, polycarbonate windshields are generally secured to the pinchweld using countersunk screws. Although it makes for a secure fit, it doesn’t always make for a waterproof or air-tight installation. This isn’t as bothersome on a utilitarian race car, but would pose a major nuisance in a daily driver.
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