Change Your Tires! Airless Tires From Michelin, Quieter Tires From Bridgestone
The EV revolution has disrupted our idea of what a car should be, but the tires they ride on have remained mostly the same pneumatic items used for decades. Some tire manufacturers have tried to lower the rolling resistance of their tires to help increase the range of electric cars but they still are subject to punctures and damage from road hazards like potholes.
Return Of The Tweel!
Early in the 21st century, Michelin unveiled the Tweel, which combined the wheel and tire into one piece and did not depend on air pressure to operate properly. According to Wikipedia, “Potential benefits of the Tweel include not only the obvious safety and convenience of never having flat tires, but also, in automotive applications, the Tweel airless tire has the potential to be able to brake better — a significant performance compromise that is inherent to pneumatic tires.
“Unlike a pneumatic tire, a Tweel can be designed to have high lateral stiffness while simultaneously having low vertical stiffness. This can be achieved because, in the design elements of a Tweel, the vertical and lateral stiffness are not inseparably linked and can thus be optimized independently. Because there is no air bladder under the tread, tread patterns can, if desired, even incorporate water evacuation through holes in the design thus eliminating or significantly reducing hydroplaning.
“Michelin expects the tread to last two to three times as long as a conventional tire. Because the tread rubber around the outer circumference is replaceable when worn (as opposed to disposing of a whole worn tire), the potential environmental impact of a Tweel airless tire can be less than that of a conventional pneumatic tire.”
That last part is significant. Having a replaceable, longer lasting tread means much less waste. The qualities that make conventional tires so durable also make them almost indestructible. Hundreds of billions of them are dumped in landfills around the world, where they are breeding grounds for infectious diseases and a threat to surrounding neighborhoods if they catch fire.
Michelin has had some success with the Tweel for low speed, commercial applications like fork lifts, lawn mowers, and other power equipment, but it has not been able to crack the passenger car market. Until now. It has developed a new version it calls Uptis, which stands for Unique Puncture-proof Tire System which uses a combination of rubber and composites to create a mesh-like structure between an aluminum hub and the tread.
Michelin says the Uptis rides just as comfortably as a normal tire but has several significant advantages that may make it ideal for electric cars and the self-driving cars of the future. Because it doesn’t rely on air pressure, there is no need to worry about punctures or road damage, which translates into not having to equip cars with air pressure monitors, spare tires, and jacks.
Saving weight is a key criterion for EV manufacturers. The structure of the Uptis can be varied to meet the specific needs of each manufacturer — more lateral stiffness for sports models, more comfort for around town driving, or lower rolling resistance for maximum range.
According to Autoblog, General Motors says it will begin testing a fleet of Uptis-equipped Chevy Bolts in southern Michigan this year with an eye toward making them available as an option on production cars by 2024. Engadget points out that the biggest advantage of the Uptis technology may be for use on autonomous robotaxis where they will eliminate downtime due to flat tires. For more on the Uptis, check out this video from Michelin.
Quieter Tires From Bridgestone
Electric cars are so much quieter than their gasoline and diesel powered cousins that drivers hear things they never did before, things like wind noise and the sound of the tires on pavement. It turns out much of that tire noise is caused by air getting trapped and compressed by the tread as it rolls along the pavement, according to Dale Harrigle, the chief engineer at the replacement tire division of Bridgestone. When that air is released, it creates lots of tiny popping noises that just so happen to be in the same frequency range as normal human speech. “This makes it aggravating to communicate in vehicles,” he tells Wired.
In developing its new Turanza QuietTrack tire, Harrigle says Bridgestone engineers encircled the tire with a few thin, longitudinal channels, and lots of short, diagonal grooves leading to the tire’s shoulder. The orientation of these lateral grooves is crucial. The ones along the shoulder allow air to escape as it rolls, so it doesn’t get compressed. And the grooves come in three different widths, measured so they interfere with one another’s sound pattern. This interference pattern reduces noise in the frequencies that are similar to human speech.
Finally, Harrigle and his team found that by molding millimeter-high serrations into the trough of each channel, they could break up the high frequency sounds that occurred as the tire interacted with the road. As an added benefit, those serrations improve traction in snowy conditions.
The QuietTrack tires cost about $133 a piece, a fairly normal price for a modern passenger car tire. If you drive an electric car and want to lower the noise inside the cabin of your car, consider a set of these new Bridgestone tires when it’s time to put new sneakers on your ride. If any CleanTechnica readers do so and want to share their opinions about the difference between their new Bridgestones and their previous tires, we would be happy to hear from you.
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