Why Are Vehicles Still so Heavy? Blame Manufacturing Infrastructure

Car manufacturers have achieved significant fuel economy gains in recent years, but the improvements largely come down to upgraded drivetrain efficiency. Vehicles still weigh substantially more today than they did in the early 1980s, when the previous decade’s demand for fuel economy improvements forced the issue.

Since then, automobiles have gradually packed on the pounds — negatively offsetting the technology encouraging fuel frugality. Modern safety concerns, improved build quality, sound dampening, and consumer demand for bigness have all helped to keep the typical family transport oinking around a two-ton curb weight.

If companies could effectively slim down those autos, without sacrificing structural rigidity, safety, or consumer comfort, the efficiency gains would become all the more significant. However, with few consumers ready to dive back into noisy, frail hatchbacks, weight savings will likely need to be done on the molecular level. In a new study, the Center for Automotive Research (CAR) in Ann Arbor investigated the materials going into 44 separate 2015 model year cars and asked automakers what would they use if they suddenly needed to reduce weight from essential items.

Accomplished with the support of nine automakers, the study investigates individual parts on various production vehicles. While the automakers provided extensive information on the components and their assembly, CAR was forbidden from disclosing the specific models used for the study. However, CAR claims the chosen vehicles are common on public roads and comprise over half of the U.S.’s car sales volume.

“If you really have to get lighter weight vehicles, there is a huge shift to composites, and especially carbon fiber,” Jay Baron, CEO of the center’s research group, told Automotive News. “Even in pillars and crossbeams and rails.”

Baron said the message he received from automakers was, “We cannot get to a 15 percent lighter weight car without getting very aggressive with composites.”

The National Highway Traffic Safety Administration’s safety regulations and the Corporate Average Fuel Economy standard are a big part of why cars haven’t gotten much lighter in recent years, but absolutely need to. With average fuel economy guidelines destined to increase to 54.5 miles per gallon by 2025, automakers would certainly benefit from weight reduction.

However, the most common weight-saving measures have come from lightening the engine itself through the use of temperature-resistant plastics (and by shrinking the motor’s overall size).

The study indicates that most automakers turn to steel and aluminum when asked to reduce a vehicle’s weight by 5 percent. Ford has already made use of an entirely aluminum body for the current F-150 and further cut weight by introducing hardened plastics elsewhere, but aluminum’s lack of durability limits its advantages and ease of enactment.

Magnesium could also use the existing steel-based fabrication infrastructure but, with so much of the production based in China, the potential for a supply disruption makes high-volume use unfeasible. It also carries a higher than average cost.

Carbon fiber and similar composites offer the greatest benefit in weight reduction, but carmakers agreed that it is also the most difficult to incorporate into large-scale production. Embracing composites as a core building material would require the abandonment of existing manufacturing methods while increasing the accepted variation in part-to-part fabrications. There is also an incredibly high material and fabrication cost.

Companies agreed that the largest barrier to lightweighting was the initial capital investment toward changing manufacturing norms. With that in mind, the trend over the next ten years should progress with the introduction of lighter materials in key structural areas like the doors, hood, front pillars, and fenders. Still, Baron told AN, the materials used will likely remain steel-based for the time being.

“They say, ‘We worked hard to get standardized processes, and now that we have them you want us to make a composite door?’ It’s not standard, so you’re disrupting the process.”