Windshield Repair Forum

How much force does it take to crack a windshield. I hit my buddy's Pontiac G6 on the driver's side of the windshield with an open palm (not a fist) and he says I cracked this windshield. The crack is in the middle of the windshield not where I hit it. Is it possible for someone to crack the windshield in that manner without it being defective or already cracked? I like to think I'm strong but I thought windshields could take that kind of impact.

I do not think there is a definite answer on "how much force does it take to crack a windshield", but first let me ask does the damage on the windshield have an impact point. If it does not have an impact point it sounds like it could be a stress crack. According to the Repair of Laminated Glass Standard a stress crack is “Any crack that extends from an edge and lacks an impact point”. Typically stress cracks occur from a windshield being improperly installed.

P.S. get out your wallet and buy the guy a windshield

This reminded me about a time when I was a teenager. I had a short temper and it usually didn't take much to set me off. Anyway, one day I was sitting in my '79 T/A and something sparked me and I hit the windshield with my fist and just like that the windshield shattered as if it was hit with a softball. The damage to the windshield was about 8" in diameter and looked like a spider web. My stupidity cost me around $250.00. The point being, I don't remember hitting the windshield with a lot of force. I guess I hit it with enough force and just in the right spot to cause the damage. I remember sitting there and saying to myself I didn't hit that hard but I guess I did.

In hot weather, the interlayer of laminated glass becomes very soft and makes it easier to break. Regarding the first post, it would be very unlikely that a slap hit at the side will break it in the centre. Look for an impact point directly on top of the crack, which may only be the size of a pin head and probably within 2" from the edge of the glass. Stress crack could be another cause but usually occurs within a week or two of the screen(windshield) being fitted and comes off the edge of the glass at approximately 90 degrees.

In your post you did not say where the crack in the center originated (top or bottom), or if it happened when you hit it or later and how much later.

Back in the late 70's, early 80's there was a lot of stress cracks in windshields. The manufacturers were trying to make their cars lighter and more efficient. The result had many different problems like doors, hoods and fenders falling out of line...and windshield stress cracks at the top near the center. At that time the Uni-Body was in its youth and far from perfected. Today GM and others are all striving to meet MPG standards as well as the burden of competition. These days even though windshields are an integral structural element of the vehicle, it doesn't mean that the body does not flex during hard driving and expansion / contraction due to heat and cold.

Now, if you hit the windshield on the driver’s side, it and the body could have flexed enough for the windshield to give at its weakest point...top center. It’s likely that it did crack but was unnoticed (blind run) in the shaded area. Thereafter it was only a matter of time before it ran out. G6 zoom zoom driving creates pressure and flexing enough for the blind run to crack out but, not enough to break on it's own without previous damage.

It’s obvious you signed onto this board to look for a way out of your dilemma and use our responses to justify your dumb act. Man up, suck it up and buy your buddy a new windshield, not the co-payment on "his" insurance, but full price.

You'll teach yourself a lesson in self control, ethics and respect for other peoples property. As a bonus, the respect and friendship of your "buddy" will be intact.