What, Exactly, Is an Automotive Platform?05/17/2021
“Platform sharing.” Sharing anything suggests altruism or ecological benevolence. Sharing an automotive platform or architecture therefore seems like a good thing, while the closely related phrase, “badge engineering,” is loaded with negative baggage. A Cadillac Cimarron was a cynically badge-engineered Chevy Cavalier unworthy of its wreath and crest, while we’re all thrilled that the fun-loving Toyota GR Supra coupe shares the BMW Z4 roadster platform.
In the early days of automotive platform sharing, defining the platform was easy. The rolling chassis of Volkswagen’s humble Beetle easily rolled right under the Karmann Ghia’s stylish coupe bodywork, and the bare-bones Citroën 2CV platform underpinned the fancier Dyane, the funky Ami 6, and the Méhari off-roadster. Automotive evolution has complicated the task of defining an automotive platform or architecture in the years since, but let’s give it a shot.
What Defines an Automotive Platform or Architecture?
Different companies define platforms and architectures differently. American automakers classically defined “platform” as a set of critical shared dimensions between the front axle centerline, the cowl, and the driver’s hip-point; “architecture” connoted the hardware placed within those dimensions (chassis, floor pan, powertrain, etc. ). Global manufacturers often blur those distinctions, and so will we.
The basic motivation for sharing an automotive platform or architecture is to maximize return on engineering investment. Leveraging the expense of developing the unseen structural elements—everything that supports the bodywork, mounts the powertrain and suspension, and provides the vehicle’s crash protection—across several different vehicles allows manufacturers to generate sufficient sales volume to deliver economies of scale. This reduces costs, maximizes profits, and if done right can allow a family of vehicles to be built on the same assembly-line equipment. Commonizing assembly-plant equipment simplifies workforce training and can improve product quality, too. It can also improve global manufacturing flexibility, allowing production of popular models to be expanded easily to other factories building the same platform.
The Evolution of the Automotive Platform
Body-on-Frame Platforms: The automobile’s horse-drawn wagon ancestry gave us this type of construction. Rolling chassis formed platforms that were often shared, possibly after stretching or shrinking the lateral or longitudinal frame members. It was comparatively easy to mount various powertrains to and drop different bodies onto these early “platforms.” Examples still in production include the truck platforms shared by Chevy and GMC, and the full-size body-on-frame SUV platforms in use at General Motors and Ford.
Unibody Platforms: In the middle of the last century, manufacturers started integrating the chassis structure with the body, which generally improves structural rigidity and can reduce weight. This forced a change in thinking about what gets shared. When these employ front and rear subframes to support the powertrain and suspension, these parts are an obvious choice for sharing. Today, generalized hardpoints get shared—attributes like the front-wheel centerline, cowl-point, driver hip-point—plus the general powertrain location and drive wheels. These things help determine how and where the crash structure needs to be, and that structure is expensive to develop. The many different variants of the Toyota New Global Architecture (TNGA) are examples of this type of shared automotive platform.
Modular Platforms: Today many manufacturers talk about modular automotive platforms, which generally refers to a platform architecture designed to accept widely differing propulsion system modules. Volvo’s Compact Modular Architecture (CMA), for example, supports pure combustion and fully electric versions of the XC40.
What Differs Among Shared Platform Architectures?
The trend today is toward allowing greater differentiation. Lee Iacocca’s “New Chrysler Corporation” emerged from bankruptcy in the 1980s largely thanks to having developed myriad K-car automotive platform variants for dirt cheap. The K family derivatives primarily varied in wheelbase and length, allowing only minimal variation in width. This left the smallest compacts (the Dodge Shadow/Plymouth Sundance) too wide and heavy to be competitive, while the most luxurious models (the Chrysler Imperial and New Yorker Fifth Avenue) appeared cartoonishly narrow next to their Cadillac and Lincoln competition.
Today’s best automotive platforms can vary widely in wheelbase, track, height, and curb weight. Volkswagen’s transverse-front-drive MQB platform supports four dozen global models, ranging in the U.S. from the compact hatchback Golf to the three-row Atlas SUV. Those models vary in wheelbase by 13.7 inches, in track by up to 8.0 inches, in length by 30.7 inches, and in curb weight by more than a half-ton. Obviously, the bodywork needs not bear any resemblance. The corporations selling the cars don’t even have to be related, as demonstrated in the ’80s by Fiat and Saab, which jointly developed the Type Four platform that underpinned the Alfa Romeo 164, Fiat Chroma, Lancia Thema, and Saab 9000. More recent examples of this type of partnership include the Mazda MX-5 Miata/Fiat 124, and the aforementioned BMW/Toyota sports cars.
Is Badge Engineering Dead?
Nope. The second-gen 2022 Subaru BRZ and Toyota 86 remain unabashed identical cousins bearing minimal design differentiation inside or out (sales volumes for each are too small to justify retooling much more than the front fascia, grille, and lamps). On most higher-volume offerings, however, manufacturers have largely improved product differentiation on shared-platform vehicles. Chevy and GMC pickups still look uncomfortably similar, but the new Chevy Tahoe/GMC Yukon/Cadillac Escalade SUVs are better differentiated now than ever before, and their delineation increases with price—the Yukon Denali gets meaningful revisions relative to the base Yukon. Very little of what you see or touch on a Lincoln Corsair, Nautilus, or Navigator is shared with the equivalent Ford Escape, Edge, or Expedition, while plenty gets shared under the skin.
What About Electrical Architecture?
The onboard electrical architecture controlling a modern vehicle—particularly the communication networks, computers, and sensors running the infotainment, safety, driver-assist, chassis, and powertrain systems—are occasionally shared across different automotive platforms. As vehicles slowly become rolling digital devices supporting ever more sophisticated cloud-connectivity, hybridization, and as we approach full autonomy, a car’s electrical architecture and the requisite computing power to control it are becoming more expensive to develop—and hence are ripe for sharing across vehicle lines.
What About Electric Vehicle Skateboards?
Manufacturers are beginning to develop “skateboard” electric-vehicle chassis that incorporate the battery, motors, suspension, and most everything needed to control them in a low platform resembling that VW Beetle rolling floor-pan chassis. Electric motors are so much smaller and simpler than combustion engines, and they typically employ an equally simpler and smaller one- or two-speed transaxle—that is, presuming they’re mounted to the chassis and not directly to the wheel. General Motors is about to introduce its BEV3 and BT1 automotive platforms (launching respectively with the Cadillac Lyriq and GMC Hummer EV/electric Chevy Silverado). GM also plans to supply an EV platform to Honda, and VW hopes to share its MEB electric platform with Ford and other manufacturers.
Other EV startups like REE Automotive and Tier 1 suppliers like Schaeffler are demonstrating greatly simplified battery platforms to which are mounted corner units that incorporate by-wire-controlled suspension, braking, steering, and propulsion systems (via hub-mounted direct-drive motors). We don’t expect such systems to deliver the ride comfort and handling demanded by today’s passenger-vehicle buyers, but in autonomous passenger shuttle or commercial package delivery duty, this arrangement makes a lot of sense.
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