Why do vehicle glasses crack?

Some drivers tend to think that vehicle glasses crack or shatter on their own. However, every consequence has a cause. One of the most common reasons for vehicle glass cracking, mentioned by Carglass® customers, is pebbles kicked up by the tires of other vehicles.

Some drivers don’t notice the pebble hitting the glass and assume that the crack happened by itself. Based on data provided by our customers, we can definitively state that a chip typically occurs when a pebble hits the windshield. If the driver does not notice the chip and continues driving with a damaged windshield, moisture and dirt start to accumulate in the chip. When temperatures drop below freezing, the moisture in the chip freezes. If the windshield is suddenly thawed, the water expands and the glass cracks. The chip consists of hundreds of micro-cracks, which, when exposed to body vibrations—such as when driving over a speed bump or unexpectedly hitting a pothole—may no longer withstand the pressure and spread across the entire glass. In the event of a crack, the vehicle glass will inevitably need to be replaced.