Kia's got Soul: Platform sharing creates siblings under the skin

The basis of any vehicle is its platform, but the concept has changed over the years. At one time, it meant the solid frame upon which the body was bolted.

While most trucks are still built this way, the majority of cars, crossovers and SUVs use a unitized construction design that incorporates the body and chassis, and “platform” is used to describe their undercarriage engineering and assembly.

“The platform is modular building blocks, the parts underneath the car that most people don’t typically see,” says Orth Hedrick, director of product planning for Kia Motors America. “The geometry is critical, and it’s designed around the distance between the wheels and all that attaches to the suspension of the car. These components are part of the platform.”

Within an automaker’s lineup, two or more vehicles may share the same platform.

This doesn’t mean they’re identical underneath, but that they share common components, such as with Kia’s Forte and upcoming redesigned Soul.

“The suspension could be common between the two, but because (one is) wider, the sheet metal that ‘stitches’ the parts together changes,” Hedrick says.

“Rather than completely redo an entirely new suspension, which is tens of millions of dollars, and it performs the same function on a car that’s relatively the same size, why not use it on the same vehicle?

“It’s like Costco buying in bulk. If you can ‘commonalize’ parts that are underneath the car, your costs go down, and you can spend the money in exterior and interior (design) and features,” Hedrick adds.

The cost isn’t just in the parts themselves, but in initially creating them, since many suspension components are stamped out in enormous, expensive dies, or welded together by robots. If a part can be used over several models, it reduces the cost of creating a die or adding more robots to the assembly line to make individual parts for each vehicle line.

Once the suspension is designed, engineers will also “tune” it to each model, creating the specific ride and handling characteristics that drivers will expect from it. A luxury car will have softer springs and rubber bushings to give it a smoother, more comfortable ride, while a sportier model will have stiffer ones to create its more muscular characteristics. The steering can also be adjusted to give a more direct, “quicker” feel to a sporty model, while a mainstream vehicle will be tuned to be comfortable in everyday driving.

Other factors

Common parts across several models can also include engines, transmissions, and interior switches and controls.

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