Tech Dept.: The Latest on the Airless Tire-and-Wheel Combo
We bushwhack into the experimental-shoe frontier.
By Don Sherman / Illustration by Sean McCabe
From the June 2012 issue of Car and Driver
When Robert Thomson invented the pneumatic tire a century and a half ago, a rubber doughnut inflated with air was only one of several ideas the Scotsman proposed for softening the ride and reducing the power required to propel the carriages of his day. Thomson also suggested filling what he called his “aerial wheel” with sponges, springs, and/or horsehair to avoid flats caused by “concussion between the wheel and the roadway.”
In spite of the excellent performance provided by today’s tires, efforts persist to let the air out, once and for all. The goals are to eliminate flats, lengthen tread life, facilitate recycling, and—hold for the most tantalizing bit—improve handling.
The ultimate proof of an airless tire’s potential came in the early 1970s on NASA's Lunar Roving Vehicle. Designed by Ferenc Pavlics and constructed by GM, these 9-by-32-inch tires consisted of steel-mesh toroids (doughnut-shaped coils) attached to aluminum wheels. V-shaped titanium treads provided traction on the dusty moon surface. We’re guessing that ride quality was less of an issue than in the Earth market.
Michelin brought the idea back home in 2005 with a tire-and-wheel combination cleverly called the “Tweel” (pictured above). After spending years developing PAX run-flat tires, Michelin engineers concluded that eliminating a tire’s need for air made more sense. The Tweel consists of a thin rubber tread band reinforced by a composite-plastic belt and supported by resilient V-shaped polyurethane spokes. Introductory claims versus conventional pneumatic radials were two to three times the tread life and five-times-higher lateral stiffness with only a slight increase in rolling resistance. The Tweel’s combination of soft vertical compliance with stiff lateral resistance seemed like the answer to every handling engineer’s dreams. Michelin demonstrated Tweels on an Audi A4 and two Segway vehicles and announced that the first applications would be for military vehicles and skid-steer construction equipment. Time magazine called this one of 2005’s most amazing inventions.
Those who drove the Tweel-equipped Audi reported one shortcoming—excessive noise at high speed—which Michelin attributed to spoke vibration. Then the Tweel story changed from excess noise to utter silence. When asked for a progress report on its airless-tire research project, Michelin refused comment. Possible reasons why: The Tweel did not pan out as expected, work is under way on some top-secret military application, or Michelin is hesitant to share its findings with competitors.
Late last year, though, Bridgestone thickened the plot by presenting an airless tire concept, which it says was the result of three years of research, at the Tokyo motor show. Looking beyond eliminating flats, the company stressed the environmental benefits of using only readily recyclable materials in this tire’s design. Mimicking the Tweel, the airless Bridgestone consists of a thin rubber tread supported by flexible thermoplastic spokes and a rigid aluminum center section. Inner and outer spokes run in opposite directions to provide vertical compliance without twisting. Bridgestone claims that high-speed noise and vibration are not concerns, but there are other issues—such as how to avoid trapping debris in the spokes—before the concept can progress from light, low-speed applications to the highway.
We’re expecting that nonpneumatic tires are a decade away. Beyond their functional attributes, two things will propel them toward acceptance: Tire companies must address the growing mountain of bald tires defiling the landscape, and they desperately need a new business model. Selling advanced-technology wheels and tires has got to be more lucrative than losing money on original-equipment applications in hopes of earning a profit with replacement rubber.
I see the problem automakers are trying to overcome here not as preventing flats, but to stop people from driving around on dangerously underinflated tires. For many years cars have come with low tire pressure warning systems. Maybe take that a step further and have an automatic pressure regulating system that could reinflate a leaking tire and adjust for driving conditions.
Had to laugh when I read this article. I am 75 and when I was in my teens my father, a scientist, showed me drawings of an "air" car. They were acutally blueprints for that car. One was made in New Mexico and actually worked. The Government quickly took control of it and I never saw it again. My father made a perpetual wheel and I watched it power several "tools". Way before power tools.
The public has been robbed by the government for years. Greed.
While growing up he and his brother built a tractor that ran mostly on water. So what's new?
He invented a fishing tackle box that opened into a seat. He worked for Bendix at the time and they took it away from him. Greed. I have seen colors in a circle make a glass vibrate. Lucky me.
So when I see all these "new' ideas I just have to chuckle. Dad must be lhao. He passed almost 30 years ago. I grew up with a rotating shower head and that was in the late 40's. He made it. Just to set the record straight.
@ Don't buy me,...Actually Alex hits a really valid point. If you part in ice with standard tires the ice is just around the outside of the tire ....with these the ice would be imbedded in all those little spaces. Even if you broke free the balance would shake the doors off with 1/2 a tire loaded full of ice.
Also, I would be amazed if they have it strong enough that there isn't a ton of lateral bend when cornering.
I would love to see this as something cost effective that worked, but I think it'll work now, but just not very well. I cannot recall which airless tire it was years ago, but there was video I saw of a Hummer H1 going up a staircase and there was minimal intrusion into the cabin because the wheel could form around the edge of the steps. I remeber this because I found it odd they used an H1 with tires that had zero off road use.
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