Exploding Window in 2007 Yaris



My two daughers were driving east towards sacramento on US 80 in our 2007 Yaris when for no obvious reason the right rear passenger window (the part that rolls up) exploded spewing glass into the back seat which fortunately was unoccupied. It was a relatively hot day (perhaps near 100) and all the windows were rolled up and the AC was on. She was not passing or being passed at the time, she was not near an overpass. The heard felt and saw nothing prior to the explosion of the window and there was no proctile in the back seat. I find the rock theory hard to believe as it would have had to be a pretty good size rock and come from the front so I think they would have seen it. Toyotas are almost perfectly air tight – so could this be some kind of compression effect? Could the difference in temperature account for it?


There is either something missing from your daughters story or the window was hit by a projectile. It is possible for a very small object hitting the glass at the correct angle to easily shatter it.


There are credible tales of spontaneously shattering windows. I know of two where the insurance company paid up. However, on one of those two the damage ocurred as the car went into the narrow entrance of a parking garage, and later inspection showed that the right-side mirror was scraped and the window frame was distorted. So, I would say that insurance companies accept claims of spontaneous shattering, but I’m not really sure it happens. Perhaps the Yaris’ window had already been damaged.


The presence of the broken glass in the interior of the car would seem to suggest a projectile. Of course, it is difficult to pin down something like definitively, but I have to think that a projectile was the cause of this breakage.


I’ve heard credible tales of saftey glass shattering spontaneously. I thought it was due to unequal expansion. Saftey glass is two peices of glass sandwiched together with a binder between (essentially.) If there’s a manufacturing defect or deviation and one peice of glass is slightly different in composition or other specs as the other, then they expand at different rates when exposed to heat or cold. That could put stress on the glass, shattering it.

Whatever the case, I aggree that your daughter may be withholding something from you. However, the fact that the glass is inside the car doesn’t indicate a projectile strike at all. Go throw a baseball through a plate glass window. As it shatters, watch how some glass falls inside and some out. Only the glass that is directly struck by the baseball is propelled in the direction of its travel. The rest of the energy radiates outward from the point of impact. The glass only breaks, it is not propelled.

The glass is inside the car because the pressure of the air outside the car rushing past was higher than the pressure of the air inside the car standing still. If this weren’t true, then air wouldn’t rush into the car when you open the window. Also, the cool air inside the car has a lower pressure than outside. That causes the air to force its way in as well. As the air rushed in, it pushed the glass in with it.



Oh, by the way. Saftey glass is specially designed to multiply that radiating effect. When you hit a peice of saftey glass, the energy is carried away from the point of impact and radiated even more effectively across the glass. That’s why, in movies (or if you’ve ever seen this in real life), when an emergency arises bringing with it the need to punch out a car window, the one doing the punching always wraps some kind of clotch across his hand. If you tried to punch a peice of saftey glass as hard as you could, without the cloth, you’d guaranteed break your knuckles. And since your knuckes would turn to dust, they’d absorb the energy from the impact, and the glass doesn’t break.



The only glass in a car that is safety glass is the windshield. All the other glass is tempered glass (heat treated). That is why it breaks into many small pieces.

Here is an interesting fact about tempered glass that may shed some light on the subject.

  1. Another characteristic of tempered glass is that occasionally a light will not release immediately at the time of damage, but at sometime, perhaps many weeks, later. This adds to the surprise and amazement of by-standers since no apparent cause is immediately evident. This type of behavior is one of the factors leading to the so called “spontaneous or delayed breakage” of tempered glass.



I appologize if I confused anyone. I aknowledge the difference, however, I find it simpler to just refer to all the glass as saftey glass. You’re absolutely right, windows are tempered, which is different. But can still undergo spontaneous/delayed breakage.



Thanks Michael! This sounds like we’re getting there. Do you have a pointer to the document containing this quote?



As the daughter in question, I feel libeled! I’m not withholding anything. (Or, wait, was I not supposed to be playing with that BB gun while driving?)

No, it really happened just as my dad related it. It was spontaneous de-window-ification.

And, Dad, why are you not defending my reputation here? Sheesh.


I don’t know sweetheart, they seem to be making some good points.


Must consider all possibilities.



Dad, I think you should explain that I’m your ADULT (i.e., almost 30) daughter, not a 16-year-old menace to society.


I have looked but I cannot find the link to the site I qouted. I will keep looking it is in this darn computer somewhere.


I did not mean to imply that you were at fault in this case. I was just thinking that you may have failed to mention something that may have happened weeks before. The thing with safety glass is it might not break the day it is damaged. It could be weeks later driving in 100 + degree weather with the A/c on. I meant no disrespect. Please except my sincere appologies.


Aw, Michael, I’m sorry! I was just kidding! It’s my dad who should be ashamed of himself! Please don’t worry!


Anything can happen with glass. While coming home one evening the left rear door glass in the last Subaru I owned made a thunk and shattered into a million pieces.
This was in a deserted area with no traffic or people around and happened at very slow speed; 20 MPH or so.


It could very well have been a small rock or BB gun fired at the car, and the projectile failed to go through the window (bounced off back to the side of the road) but managed to shatter the tempered glass anyway. Thus, nothing odd in the back seat.