Fuel prices are creeping up across the country again. With the days of gasoline less than $2 a gallon a distant memory, new-vehicle buyers are once again looking at fuel economy ratings when purchasing. The demand for fuel-efficient vehicles keeps automakers such as GM working hard to find new ways to boost mpg numbers.
GM recently invited journalists to its Technical Center in Warren, Mich., to get a look at one area in which the company is focusing its efforts: lightweighting. This isn't a euphemism for not being able to hold your liquor; this is an all-out effort by the entire company to lighten new cars and trucks under development. It requires effort at every step of vehicle development — from goal setting and determining how a vehicle needs to perform, to computer modeling and material selection, to manufacturing methods and designing special tools. But most important is drumming home the idea to the hundreds of engineers tasked with developing new vehicles that every gram matters.
To accomplish GM's lightweighting goals, engineers use computer-aided simulation to design pieces of the vehicle's structure out of different metals to see how they'll perform before any parts are built. Smaller efforts such as scalloping the edges of welds and punching lightening holes in structural panels save small amounts per part, but add up to big savings for a whole vehicle. Extensive use of aluminum, several kinds of high-strength steel and magnesium allows for more creative part consolidation, while new bonding techniques are replacing welding with structural adhesive (yes, glue) and rivets. Even welding is getting attention from GM's research and development groups; the company says it's found a way to successfully spot-weld aluminum to steel — something never before accomplished in an automotive application.
The results are new cars that aren't just a little bit lighter than the ones they replace, but significantly lighter. The 2016 Chevrolet Malibu is 300 pounds lighter than the outgoing model despite being a bigger car, thanks to the above techniques. The Cadillac CT6, a car the size of a BMW 7 Series, weighs considerably less than the smaller BMW 5 Series, and includes a variety of materials. The new Chevy Volt is almost 250 pounds lighter than the first-generation model, and the upcoming 2017 Buick LaCrosse is almost 700 pounds lighter than its predecessor. That's like taking two full-sized linebackers out of your backseat.
So what does this mean for the next generation of GM pickup trucks? Although they declined to talk specifics about the next Silverado and Sierra, GM representatives offered some clues as to what to expect. The GM presentation spotlighted flexibility: employing different materials where they can best be used. Flexibility is evident in the Cadillac CT6's structure — lightweight extruded aluminum (also valued for its predictable deformation properties) are used for the front and side frame rails, but high-strength steel is used for the "safety cage" that surrounds passengers. The CT6 also uses aluminum on some body panels but steel in the floor due to its sound-absorption properties. And the ability to weld steel-to-steel, aluminum-to-aluminum and soon aluminum-to-steel using the same welding gun on the assembly line allows for even more flexibility in using the right materials in the right spot.
What we can infer from this is that the next full-size GM pickups will not duplicate Ford's efforts by going to an almost entirely aluminum body on a steel chassis. Doing so required more effort at Ford than just designing something new; it required a total tear-up of a number of production systems along with production plants. Instead, we're more likely to see the next Silverado look like the CT6 underneath — a mix of materials fashioned to take weight out of every component and panel. The benefit is that building such a truck won't require a complete tear-up of the Silverado assembly plant to put in new equipment. A mixed-material vehicle can be built on the same line as the current mostly steel one. We're eager to see what GM cooks up for the next big trucks when the new ones arrive, given the automaker's recent achievements in making its latest products far lighter than the outgoing ones.
Cars.com photos by Aaron D. Bragman; manufacturer images