Join Date: Jun 2006
Location: Eastern ON Canada
Car: 07 OBW 2.5i D-4AT
Feedback Score: 7 reviews
The "structural" connection is correct, but only for the glass that's fastened (glued) to the car body, not the windows in the doors and that can be lowered and raised.
The weight of a particular glass, such as a windshield, isn't necessarily an indicator of the its strength. A lighter glass can be "stronger" than a heavier piece -- it's all in the way it's made.
Every once in a while there's a thread here, and in other forums, about broken windshields and, inevitably, the posts turn to the frequency this is being experienced compared to previous cars. I believe one of the major reasons for this is not the way the glass is made, but the way it's mounted. Earlier windshields were installed to the body using a grooved rubber ring around the body opening. The glass was not glued to the metal, but instead "floated" in the rubber. As a result, body twisting etc did not affect the glass as it was isolated from the changes.
But now that the glass is fastened (glued) into position directly on the body, it becomes part of the structure, but also is subject to the stresses of body twists and changes. The rubber-like glue that's used should normally provide for this, but it has it's limitations. Changes in the body around the windshield will cause tension and stress to build up in the glass. Glass itself is somewhat flexible, but in severe cases, the window might all of a sudden crack with no apparent reason. In other instances, it will not, but hit the stressed windshield with a stone at high speed, and that tiny bulls-eye can quickly become a crack along the stress line(s) in the glass. This, I believe, is what leads to the thought that newer windshields, and other car glass, isn't as strong as "in the old days". But I don't think that's really the case.