There's been so much written about windshields that I can't imagine this is really a new observation, but I don't remember reading it anywhere. Sorry if I'm covering very old ground.

My windshield is cracked again but this is the first time it wasn't obviously rock chip related. The first chip was near the bottom/center of the glass and it quickly turned into a crack that spread about 8" before I had it replaced. The second chip was upper left; it didn't spread at all and I had that one repaired. This time there isn't even a detectable pit and it started at the bottom near the center of the glass.

Here's the new (?) bit. I happened to be staring at the 6" crack as I closed the door yesterday and noticed that just as the door closed the glass flexed in the center at the bottom - I saw it pop outward at least 1/8". I opened and closed the door a few more times to check it out. The glass stays stationary at the sides and flexes in the middle. The third time I shut the door the crack extended another 1/4" - same happened the fifth or sixth time. I got out and watched along the length of the driver's side wiper blade and pushed the door shut again to confirm - yup, the end near the center of the glass jumped at least 1/8".

I don't know when or under what conditions this crack started, but I know I first noticed it one morning when I got in the car....not the day before when I parked it. The cracking that happened as I was repeatedly closing the door was while the car was parked in the garage, not in motion. I know the glass will more easily flex once it's already cracked and don't have an intact windshield at the moment so I can't check to see if it normally flexes at all (if so, probably less).

Anyone seen this? Comments?