Chip and Crack Expansion

Stress from extreme temperatures, driving and fatigue will cause existing windshield rock chips and auto glass cracks to spread quickly.

Weather Stress
In cold weather, windshields will become more concave; as a result, windshield rock chips and cracked windshields are more likely to spread horizontally. Windshield rock chips are 60 percent likely to spread at 32 degrees and 80 percent likely to spread at 14 degrees. Warm weather causes these windshield rock chips to spread more vertically.

Driving over rough terrain or obstacles in the road can cause a windshield rock chip to crack. The force goes throughout the car and puts pressure on the edges of the windshield rock chip, causing it to spread. Studies suggest that stressors like weather changes and simple driving will eventually lengthen a windshield crack or rock chip.