Why Do Windshields Crack and What Should I Do if it Happens to Me?

Many of us have had the unpleasant experience of innocently driving along when an errant piece of gravel or other mysterious road debris suddenly puts a dent in our vehicle's windshield. And many of us have had the even more unpleasant surprise of the little nick becoming a five-inch jagged crack a mere few hours or days later.

Windshield replacement is one of the top insurance claims in the U.S. Surprisingly, it doesn't take much to damage a windshield. All it takes is a rock impact the size of the dot a pencil tip makes on a piece of paper to cause serious damage. So, why do this happen and what can we do about it?

Types of Cracks

Edge crack
The most common type of crack, the edge crack is the cause of 60 to 80 percent of windshield replacements. Because of how they are manufactured and installed, the outer 2 to 3 inches of a windshield (the "Crack Zone") have stress defects, which cause this area to fracture much more easily than the rest of the windshield. Even tiny cracks can become 8- to 10-inch long cracks.

Stone break
A small chip that occurs when a stone or other hard debris hits the windshield. This can develop into a large crack over time.

Bull's eye/Half moon
Circular ding, with a cone in the outer layer of glass. A half moon crack is similar, but not completely circular.

Chip
Damage by a rock that causes a small piece of glass to break off the windshield.

Floater crack
Less common than an edge crack is the floater crack, which is caused by severe temperature changes (especially cold temperatures) to stone breaks.

Stress crack
A crack that occurs without anything actually hitting the windshield. The most common causes are a large variation in temperature, like if your car has been sitting in the hot sun all day and then you blast the AC.

If you're interested in getting a quote for a windshield repair or replacement, call our friends at Safelite. They offer mobile repairs too. 877-303-3376

Does outside temperature matter?

In a word, yes. Without going too much into an explanation of the thermal coefficient of expansion, suffice it to say that a wide range of temperatures has a very direct effect on a chipped windshield. The metal in the frame of your car or truck can expand and contract at a different rate than the windshield glass. This places stress on the windshield frame, which cracks the glass further.

Should I be worried about a crack in the windshield?

Absolutely. Windshields are critical safety devices that help prevent injury and death. They not only prevent ejection during a crash, but also serve as the backboard for airbags by controlling 20 percent of the "crash pulse," which tells the airbag when to deploy during an accident. Windshields also support the roof of the vehicle, which is essential during rollover accidents.

Can you stop a crack once it starts?

Once a windshield is cracked, the stress placed on the ends of the crack almost guarantees that the crack will continue to spread along the same line, much like faults that produce earthquakes. The only exception to this is a conchoidal (dish-shaped) fracture that has no obvious outward rays. Cracks like this rarely spread. But for chips with little cracks radiating out from the center, expect it to spread out.

How much does it cost to replace a windshield? Should I do it?

According to some experts, no replacement windshield is as good as the original. Not only are many replacements done incorrectly, but the initial windshield has to pass so many government tests, that original factory installation cannot be duplicated in the aftermarket. Your best bet is to prevent replacement if possible. You can achieve this by using crack prevention products.

Many insurance companies will repair cracks for free in place of replacing the entire windshield. For cracks that are smaller than 6 inches, repair is recommended. But there are companies that offer products to repair cracks up to 24 inches long.

Chips in the windshield generally cost around $50 to fix. Cracks can cost anywhere from $100 to $200 to repair. Replacing a windshield costs hundreds of dollars and rises to over $1000 if an OEM windshield is used.

How can you prevent cracks?

If you can, park your car in a garage or other temperature-controlled environment. Leaving your car out in the sun or in the cold tends to make the edges of the glass more brittle.

If you notice a crack or ding in your windshield, have it looked at immediately! The longer you wait, the more damage you are in for.

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