Laminated Door Glasses

My son Jay recently reported a problem with laminated door glasses breaking after installation. He said he noticed that the aftermarket parts were breaking at the mounting brackets, and that the glass itself seemed to be slightly out of bend. I hadn’t heard about this before, so I did some research with other technicians and found that this was a common problem.

The reason this intrigued me is that laminated door glasses are supposed to be constructed with two layers of heat-strengthened glass and lamination. Though “heat-strengthened” glass is not true tempered glass as defined by ANSI Z26.1, it is supposed to be heat-strengthened enough to withstand the abuse put upon it by the operation of the movable door frame and glass.

This raises a few questions. Did the aftermarket manufacturers reverse engineer the laminated-door glasses correctly? Did they recognize that the glass used for door-glass construction should be heat-strengthened and not just annealed glass? If they were aware of the necessity for the heat-strengthened glass construction, did they replicate the process and use the OE specifications or weaken it for a price point?

Here is the issue as I see it. The actual purpose for making door glasses laminated, rather than tempered, is murky. Was the change made for acoustical reasons to benefit the comfort of the occupants and the performance of voice-activated systems? Or are laminated parts safety devices that act as a backstop for the side impact airbags/curtains?

Depending on who you talk to at any given time, the answer changes. It is to the benefit of carmakers to consider glass as a performance feature, rather than a safety feature, to keep free of Federal regulation.  However, if you are a car salesperson, safety sells and, if a safety reason can be attached to the feature, it may close the sale.

Now let’s look into the minds of the ARG manufacturers. If the glass you produce is a performance feature, not driven by safety, and the cost of producing a part is prohibitive to the goal of reaching a price point, then why not laminate for acoustics but weaken the strength of the glass portion to meet that price objective? It makes perfect business sense.

Heat-strengthening glass is an expensive process. You must take the process steps of strengthening the glass (like tempering) but then add the additional step of lamination. Increasing the cost of a finished product that is naturally slower selling, like a door glass, may not make financial sense. Why not eliminate one of the processes that, in some assessments, are not necessary to the safety of the vehicle to meet the price point their customers demand?

In my opinion, the heat-strengthened auto glass parts serve both performance and safety purposes. If safety is even a small reason for its existence, it is my opinion that the product used in our service of auto glass repair and replacement must meet the specifications of the OE part. So, buyer beware. When buying ARG laminated side parts, think of the primary purpose of the part and act accordingly. I prefer to err on the side of caution.