GM Had Some Of The Best Rear Windows Of The 1970s

I feel on this site we’ve talked a lot about GM, with both glowing, jubilant praise and with puzzled resignation over their weird, often bad, decisions. I’ve been accused of both being unfair to GM and sucking up to them, so I must be doing something right, or, maybe more likely, wrong. Who knows. What I do know is that sometimes GM does something genuinely interesting and unexpected, and when that happens, I want to call it out. And there is something that GM did back in the 1970s that I think deserves some special mention: they made the most interesting rear windows of the entire decade.

Yep, you heard me. I know that’s an extremely bold and wildly specific claim, but I think you’ll agree. If we look at the grand, transparent panoply of rear windows in the 1970s, you’re not going to find anything that comes as close to some rear windows GM was producing for a few coupés in that era. And it’s all thanks to one particular piece of equipment, some designer must have seen at a trade show or something and arranged to have bought and placed in a factory: a Hot Bent Wire machine.

Specifically, the Pittsburgh Plate Glass (PPG) Hot Bent Wire glass forming and folding process, which could fold automotive glass into some dramatic shapes. While maybe not origami-level, exactly, the process produced something quite different than the sort of curved glass that car design had been using for decades, and the look, with its crisp edges and folds, felt genuinely new and novel.

GM really only used this process on two cars, both late ’70s coupés: the Chevy Caprice (or Impala) coupé and the Oldsmobile Toronado XS:

Of the two, the Chevy was by far the more common one. This was the coupé version of the 1977-1979 B-body Caprice, which was much more commonly seen in four-door sedan and wagon body styles. I grew up absolutely surrounded by these cars, and I generally found them pretty boring, if I’m honest. They were so rectilinear and staid, I just couldn’t get excited about them. But somehow, the coupé was different, and it was all because of that rear window.

There was something about that rear window, with its sloping profile and prominent creases, that made the whole car much more interesting, somehow. That rear window just didn’t look like anything else on the road, and as a kid I remember seeing them and wondering how they were made. Were they composed of three pieces, somehow adhesive’d together? Melted? They absolutely caught my attention.

The slope of that window gave the profile of the caprice a lot more sleekness, and the prominent creases of the folded sides made the window fit in with the design vocabulary of the whole car. If you are skeptical of my claim that this window was the defining stylistic element of the car, just look at what happened when GM replaced it with a boring old flat window with the redesigned B-body of 1980:

Tell me the car doesn’t lose something when they went to the flat window. That fastback glass adds so much to the car – sleekness, airiness, a visual element to focus on – and without it, that car is just difficult to really care about. Also, looking at these now I’m remembering how much GM loved those wire wheels. Oy.

The PPG hot wire machine also got some use from Oldsmobile, who used it to bend the rear glass of their Toronado XS into a dramatic wraparound rear window. This idea first came around with an experimental concept, the Oldsmobile Toronado XSR, which also featured power-retractable T-tops. This car was modified by American Sunroof Company (ASC), and only a few were actually built, in numbers that range from three to 12, depending on your source.

While the XSR with its powered T-tops never made it to market (those powered, retractable panels would have been complex, leaky nightmares, most likely), a version with a normal, solid hardtop (or a conventional sunroof)  did make it to market, the Toronado XS. Of course, they only made about 2,100 of those.

That’s a hell of a rear window, right? Oh, and it’s also worth noting the high-mount brake and turn signal lamps that were set into the bodywork just under the rear window, almost a decade before high-mount stop lights were legally required! That’s some taillight innovation there, too!

That panoramic rear window gave the interior a very open feeling, no small feat in a car whose interior color and upholstery choices made it feel like someone crammed a bordello into an office cubicle:

Here’s a nice video walkaround/through of an XS so you can get a better idea.

GM returned to the PPG bent glass party trick in 1986 with the Chevy Monte Carlo SS Aero Coupe, where the addition of a bent-glass fastback rear window let them quickly and cheaply improve the car’s drag coefficient from 0.375 to 0.365, which is pretty good for just replacing a window. Well, a window and rear trunk lid, but that’s still getting off really cheap. I can’t think of any modern cars that are using this method of folding glass; smooth, graceful curves are more the norm now, but I think there’s still a place for these kinds of crispily-creased windows in cars. Maybe GM will be bold once again and give it another go.

Top graphic image: Wikimedia Commons