Windshield replacement is getting out of hand - cracks...

[EAV1]

Was going to start a new thread, but decided to just share my experiences here. I had my previous M3 for three years. During that time I had to replace the windshield twice and the back glass once. The "record" was the second windshield replacement when the glass had one larger crack and six small rock chip marks (that could have been fixed in 15min if not the larger crack). My new M3 has already during its first month had one rock chip mark repaired. For comparison, I drove my pre-Tesla car for 16 years and had zero windshield replacements and possibly zero rock chip marks. My driving patterns have been fairly similar for the last 20 years.

 

[nate704]

My driving patterns have been fairly similar for the last 20 years.

Everything else has changed dramatically, and the windshield crack doesn't happen until it happens.

 

[Eka A]

Multiple replacements often means the frame isn't straight. That means the glass has bending tension in it. So when it gets chipped, the crack rapidly grows.

 

[zoomer0056]

Multiple replacements often means the frame isn't straight. That means the glass has bending tension in it. So when it gets chipped, the crack rapidly grows.

That sounds like a reasonable assumption and cause for a buyback.

 

[nate704]

Multiple replacements often means the frame isn't straight.

No.

that means the glass has bending tension in it.

Car chassis always flexes in every direction which will put some kind of force on the windshield all the time, and yet windshield doesn't get cracked all the time.

So when it gets chipped, the crack rapidly grows.

No, it depends on so many other things. if the chip is deep enough, it will grow or location can make huge difference or temperature can make difference, etc.

 

[Pianewman]

My car has had a chip since mile 80. Now at 53800 miles. Chip hasn't changed.

 

[Eka A]

No.

Car chassis always flexes in every direction which will put some kind of force on the windshield all the time, and yet windshield doesn't get cracked all the time.


No, it depends on so many other things. if the chip is deep enough, it will grow or location can make huge difference or temperature can make difference, etc.

Glass has limits for how much it can flex. Put it on a bent frame, and it's already used up some of that flexibility range. Drive around and it may flex too much. If the frame was fine, then it would have stayed within the limits. I've designed equipment where I was flexing glass as part of the operation of the device.

PS, you don't need a chip. Just a stress riser point to push past the limits of the glass.