Talk to a car designer from 1985, and he’d tell you that an 18" wheel was something for off-road pickups. Today, it’s a common size on sedans and an option on specialty model compact cars. In 2001, the smallest wheel available on a Toyota Camry sedan was 14". Today, the smallest Camry wheel is 16", a 14% increase.
Big wheels look good, offer better traction, and lead to better vehicle handling. But as the radius of that circle gets larger, the amount of material and weight going into each wheel increases, lowering fuel economy and reducing the load-carrying capacity. This puts pressure on car designers who want to make vehicles look as flashy as possible but need to cut weight to meet fuel-economy regulations.
“The size of the wheel product has been growing and going in the opposite direction of lightweighting, so we needed something that could offer design freedom while compensating for increasing wheel diameters,” says James Ardern, director of business development for Lacks Wheel Trim Systems, a wheel supplier to the global auto industry. “Designers are always going to push the boundaries, and that’s going to mean bigger wheel diameters. If they do that, they’re going to need to find ways to cut wheel weight.”
Cool, light wheels
Engineers at Lacks design composite wheel surfaces that bond to aluminum alloy wheel structures, creating lightweight yet ornate coverings. Ardern stresses that the composite face bonds permanently to the aluminum surface, creating a single-piece assembly, not a modern version of a hubcap.
Throughout the past decade, automakers have retired almost all of the painted steel wheels that used to be industry standards, replacing those with aluminum alloy wheels. Swapping steel for aluminum kept wheel weights down as designers expanded sizes, but it limited design creativity. Because aluminum is harder to shape than steel, many of today’s alloy products have flatter appearances than products from the ’60s and ’70s. Ardern says Lacks’ system promises a return to those showier days without the weight penalty.
Designing composite surfaces allows for a wider array of patterns and shapes than aluminum. Sharp corners, deep surfaces, and complex shapes are limited by what can be cut into an injection-molding die, not by limitations of the material itself, he adds.
More importantly, the composite structures are significantly lighter than aluminum wheel faces. Typically, designers can save 20 lb to 40 lb per vehicle (5 lb to 10 lb per wheel) by replacing the visible aluminum design surface with Lacks’ advanced composites.
“The wheel is one of the only components that’s under the springs. Reducing that unsprung mass can be more beneficial for fuel economy than taking weight out of the doors or roof,” Ardern says. “The rotational inertia of the wheels make that weight critical to determining fuel economy.”
Tooling and equipment costs are also lower with composites than with stamped or forged aluminum structures, Ardern adds. Those lower costs make it possible to support more low-volume wheel runs for specialty products such as hot-rod versions of mainstream products, off-road editions of pickups, or limited-edition anniversary specials for classic cars.
“You don’t have to design and prove out every part of the system,” Ardern says. “You can just change the finishes to offer a chrome or carbon-fiber look. Or you could change the design surface without having to change anything else. The turnaround times are nothing compared with what the industry used to deal with.”
Auto designs have a shorter shelf life these days than they did 20 years ago, with models going through mid-cycle design upgrades as quickly as three years after launch. Ardern says new wheel designs, coupled with new colors and possibly a new grille, can make older designs look fresh for a significantly smaller investment than a more thorough re-working of the car’s exterior.
“There are thousands of exterior parts on a vehicle that drivers see, but wheels have a real emotional element,” Adern explains. “They’re not just the functional base of the vehicle, they communicate a lot about the look, the entire design philosophy at play.”
“The aluminum wheel structure is a safety critical part, so we don’t want to alter that basic function. But we can optimize the aluminum use to eliminate a lot of material and gain some weight savings,” Ardern says.
Wheel surfaces also need to resist scratching and cracking, which is perceived to be a negative as it relates to composites.
“These wheels are on pickups and SUVs, the most demanding vehicles on the road,” Ardern states. “Customers would notice right away if this were a SnapTite model, especially with those duty cycles. Our technology is robust and sturdy because it needs to be in those applications.”
The Lacks’ wheels have a foam core behind their composite surfaces, and Ardern says the company’s engineers spent a lot of time and effort so that foam can mimic the sounds of solid-metal structures.
“It sounds and feels like a traditional metal wheel. If you flick it with your fingernail, you get that ping you’re expecting,” he adds.
Lacks Wheel Trim Systems
About the author: Robert Schoenberger is the editor of TMV and can be reached at 216.393.0271 or firstname.lastname@example.org.