Way back in 1973, General Motors introduced the third generation of its popular C/K-line pickup trucks. Badged as both Chevrolet and GMC, they were a more than fitting replacement for the short-lived, second-generation “Action Line” trucks built between 1967 and 1972. They combined increases in comfort and utility with handsome, muscular, broad-shouldered styling to create what would become an icon of late-20th century automotive design. These new “square body” pickups, as they’d come to be called, made up the backbone of GM’s light and medium-duty truck lineup for 14 years and underpinned everything from half-ton pickups to Blazers and Suburbans to dump trucks.
Square bodies were phased out over the course of a few years at the end of the ’80s and were replaced by the General’s fourth-gen GMT 400 trucks. While the GMT 400 was a pretty big step up in quality, comfort, and styling, it carried over one of its predecessors more controversial styling cues — square wheel wells. In fact, GM put square wheel wells on its trucks for nearly 50 years, from the introduction of the square body in 1973 until the launch of the fourth-gen Silverado in 2019.
So, why square — or, well, rectangular with round corners — wheel wells? Truck nerds have been arguing about that for longer than I’ve been alive, and I’m a bicentennial baby. Go to any online forum, pick ‘n pull, or Elks bingo night and ask the first two gray-bearded, square-body partisans you find about their opinion on GM’s wheel wells, and you’ll get three different opinions. There is an actual, factual reason though, and despite what your uncle thinks, there’s a pretty simple explanation for it.
Science!
Throughout the postwar era, most of GM’s trucks featured round wheel wells just like Ford, Dodge, and Studebaker trucks did. While there were some outliers here and there in the lineup — early-60s first-generation C-series trucks had square-ish wheel wells — GMC and Chevy wheel wells were as round as the tires within them from the time GM restarted civilian production until the birth of the square body. As stated above, it all changed in 1973 with the introduction of the third-gen C/K-series.
Why, though? Why did GM put square wheel wells on its new truck and stoke more than half a century of boring-yet-strangely-heated arguments? The answer is surprisingly simple — aerodynamics. See, the square body was apparently the first GM truck to undergo wind tunnel testing during its development. Yeah, yeah, “hurf-blurf squares aren’t aerodynamic”. Listen, GM tested square bodies in the wind tunnel in the early ’70s, did a bunch of fancy math, and figured out that the square wheel wells were sufficiently aerodynamic. So much so, in fact, that GM kept the wheel wells square for almost half a century. That’s dedication to the bit right there.
GM abandoned rectangles and brought the new Silverado to market in 2019 with their first round wheel wells since Nixon was in office. Why the change? Again, aerodynamics. Five decades worth of research, improved technical and scientific understanding, and even fancier maths showed that the new Silverado’s round wheel wells were aerodynamically superior to those of its predecessors. That’s the way it goes with science — things are true until they’re proven untrue by someone smarter and better equipped than you. It’s how we learn, and it’s how we make our trucks better (and solve long-running arguments).
