Sam Landers, chief tire engineer at Goodyear Tire and Rubber, has an unsettling way of putting traction in perspective: Think about your big automobile on a rainy day. Its only contact with the road is four patches, each about the size of your hand.
During a downpour, he explains, each of those small contact areas must claw through a sheet of water to keep a grip on the road. At highway speeds each tire has to muscle aside a gallon of water every second; otherwise, a wedge of water can build up in front of the tire, providing a little surfboard for the wheel. When the tire begins riding on this wedge of water instead of the road, the car is hydroplaning, and the driver has lost control.
Tire treads are supposed to fight this tendency. Stroll through a parking lot and you’ll see dozens of tread patterns, each with tiny canyons and mesas designed to shatter and disperse the film of water on wet roads. But the overall geometry of the patterns, and their resulting effectiveness, varies only slightly from brand to brand--until you get to the Goodyear Aquatred.
There’s nothing subtle about the inch-wide, one-half-inch-deep channel that makes the
Aquatred look like a pair of Siamese-twin motorcycle tires. This central groove--dubbed the aquachannel--gives the tire its uncanny ability to hug a wet road. Water that would otherwise form a hydroplaning wedge funnels into the groove and jets out through side channels that branch to the edges of the tire. The result: cars equipped with Aquatreds stop up to 20 percent faster on a rain-slick road than those with conventional tires, according to Goodyear’s tests.
In the late 1970s, says Fred Kovac, Goodyear’s vice president for tire technology worldwide, a group of people at our technical center in Akron, Ohio, got their minds working on trucks that had double tires at each wheel position. We knew the double tires resisted hydroplaning because of the huge groove between them. I began to think, Is it possible we could put these two tires together as one? I gave that assignment to Sam Landers.
Landers led a team of Akron-based engineers who molded a prototype in time for a 1983 concept car. But another eight years would pass before the tires hit the streets in quantity. What Landers had to do was fine-tune the design so that the wet-traction requirement didn’t cause other problems.
Tire design is an exercise in trade-offs, Landers explains. Tires that are sculptured aggressively for good traction tend to create a lot of noise. When a tire is rolling, the spaces between tread blocks hammer the asphalt on the way down and vibrate as they swing around back up.
But on Aquatred, Landers softened the leading edges of the tread blocks to dull the hammering and secured them with rubber bridges that dampen the vibrations. The bridges also contribute to traction, he says. When you put a load on a traditional tire, the grooves tend to pinch closed. The bridges on the Aquatred are strategically placed to hold those grooves open.
Both tire engineers and consumers must contend with another trade-off: the inverse relationship between traction and tread wear. The channels carved into a tread pattern subtract from the surface area of a tire. The weight load of the car is concentrated only on the segments of rubber that actually make contact with the road, so these parts of the tire take the heaviest punishment from abrasive friction. Without further design, the Aquatred’s central groove would have displaced a significant load to the tread blocks on either side. Landers countered this problem, however, by making the tire slightly wider, so that its total footprint is roughly equivalent to that of a standard tire.
What’s more, selecting the composition of tire rubber normally means choosing between good traction and durability. Typically, when you have a high-traction rubber compound, it’s softer, says Landers. It adheres to the roadway, and because of that it leaves small bits of rubber behind. Unwilling to compromise on tread wear for the sake of traction, Goodyear’s researchers developed a new compound, a three-chained polymer called styrene-isoprene-butadiene rubber. Styrene-butadiene is the classic synthetic rubber; originally concocted during World War II, it is a compound molecule that links styrene’s traction characteristics with butadiene’s wear resistance. Isoprene, the building block of natural rubber, lends extra toughness and flexibility.
If you blend them together, Landers says, you normally get the worst of both worlds. But Goodyear’s chemists managed to slightly alter each of the ingredients at the molecular level, so the positive characteristics of each remain when they’re mixed. The result: the three- chained polymer offers better wet traction than conventional tire rubber, and yet Goodyear is so confident about the compound’s wear resistance that it offers its highest warranty--60,000 miles--on Aquatreds.
Setting up an entirely new manufacturing process to produce large quantities of the new rubber was one factor that slowed the introduction of the Aquatred. Another was the time needed to create enough of the radically new Aquatred molds for a workable factory, in Union City, Tennessee. In early 1991 Goodyear went into full-scale production, and the Aquatred premiered that fall.
We all believe this is an industry breakthrough, a startling new tire, says Kovac. More than 20 percent of the 6 million auto accidents that occur in the United States each year happen on wet roads. About $90 a tire seems a small price to pay to keep a grip on the road.
Jim Lutz, program manager at General Motors Advanced Engineering in Warren, Michigan, for the development of the Ultralite concept car. This 1,400-pound, four-passenger sedan achieves more than 100 miles per gallon on the highway, can reach 130 miles per hour, and exceeds the strictest tail-pipe emission standards now on the books. The Ultralite body is constructed from six strong yet lightweight carbon-fiber panels mated to a litany of other low-weight components, including the engine block and wheels.
Hideyo Miyano, deputy general manager of research and development at the Honda Motor Company in Tokyo, for the development of the 1992 Civic VX Hatchback VTEC-E engine. Utilizing a finely timed valve control system and new lean-burn combustion technology, the new Honda engine achieves 48 miles per gallon in city traffic and 55 miles per gallon on the highway-- the most of any four-cylinder automobile available in the United States. Burning smaller amounts of fuel at lower temperatures should have resulted in less power from each of the engine’s cylinders, but by creating a special swirl of the air/gas mixture as it enters the combustion chamber, Miyano’s engine extracts the maximum amount of power from every drop of gas.
John W. Gardner, manager of applications engineering at Noise Cancellation Technologies in Linthicum, Maryland, for the development of the Electronic Active Muffler. Unlike conventional car mufflers that force engine exhaust through a maze of baffles to reduce noise, the electronic muffler attenuates sound by creating a sound wave equal but opposite to that of the engine’s noise, effectively canceling out unwanted sound. And because the electronic muffler eliminates the back pressure created when exhaust gas is channeled through a conventional muffler’s baffling, the antinoise system also improves engine performance and efficiency: more horsepower can be produced with less fuel.
Hugo Mellander, safety engineer for Volvo in Göteborg, Sweden, for the development of Volvo’s Side Impact Protection System. While side impacts are the second-highest cause of death in car accidents, they present the most difficulty for engineers: there’s a very small space between the occupant and the point of impact. By spreading the energy from a crash across a greater portion of the car’s structure, this new system reduces the forces reaching the occupants in a side-impact collision. Key parts of the frame are reinforced and moved to spread impact forces harmlessly to the roof and floor of the vehicle. Volvo engineers estimate that 25 percent of side-impact fatalities will be avoided in such cars.