Tires of the Future: What Will EVs and AVs Roll On?

The humble pneumatic tire dates back to the 19th century, first deployed (albeit on a bicycle) in 1888 by a gentleman named John Boyd Dunlop.

Yes, that Dunlop.

Believe it or not, 135 years later scientists are still mastering the black magic of tire dynamics, resulting in new shapes, treads, compounds, and constructions. Many of the amazing lap records set at places like Germany's famed Nürburgring have more to do with modern tire advancements than anything else, but most manufacturers these days are focused more on tire efficiency than outright performance.

While the latest generation of EVs look and drive much like their internal combustion predecessors, their heavy weight and remarkable torque put special demands on tires. Meanwhile, EV owners want rubber that offers not only good grip and overall dynamics but also low noise and excellent range.

Looking even farther down the road, future autonomous cars have their own needs, including more advanced sensors and feedback mechanisms to report real-time road conditions to drivers that only exist on a computer chip.

Let's dig into how some of the biggest tire manufacturers in the world are addressing the needs of modern electric cars while also preparing for our autonomous future.

Tire Specialization and Design

The number of cars on American roads has risen significantly over the past 20 years, from roughly 225 million to 278 million today, and the specialization in their tires has expanded at an even greater rate.

"SKU proliferation in the tire industry has exploded," Steve Bourassa told us. He's director of products at Nokian Tyres North America. "Rough estimate here: 20 years ago, we were probably looking at 160, 175 sizes that made up the market. Now we're over 600 sizes total that consumers can potentially choose from to put on their vehicle."

That's just sizes, ignoring all the variety of manufacturers and individual model tires within, different compounds, constructions, and tread patterns, including specialty tires like Nokian's new Hakkapeliitta 10 EV, a variation on the company's studded snow tire designed for EV use.

This specialization demands new, faster, more efficient methods of design. Bourassa said that Nokian engineers are increasingly relying on virtual modeling, using aspects of artificial intelligence and machine learning: "If the models are working the way that they should ... all of a sudden tire manufacturers can reduce our overall costs in real-world testing and do a whole lot of that early modeling in advance." Bourassa said that this could lead to "some potentially crazy experimentation and developing new types of tires and new technologies in future developments."

What kinds of new technologies? How about tires that don't need air?

Are You Down With NPT?

The notion of airless tires is nothing new. In fact, the very earliest "tires" were just bands of leather or steel. Lately, though, the concept of the non-pneumatic tire, or NPT, has been making something of a comeback.

The basic idea of an NPT is to still offer a wheel and a tire of sorts with tread that rolls along the ground. However, instead of pressurized air held in by a sidewall, airless tires rely on an open mesh of composites or polymers, allowing a similar level of flex to a pneumatic tire without the risk of puncture.

Michelin has been a strong proponent of this area of research, introducing its airless Tweel design back in 2004 then putting it into production for industrial use a decade later. Now, the company is developing its so-called Uptis, or Unique Puncture-Proof Tire System, for potential consumer use.

"Uptis was tested up to 130 mph on standard law enforcement vehicles in Europe—showing a lot of promise for future real-world application," Michelin's technical communications director Russell Shepherd said. Michelin has signed a partnership to put 50 sets of Uptis on DHL delivery vans in Singapore this year for further testing.

While the durability advantage of an airless tire is clear, there are some drawbacks to NPTs, particularly when it comes to EV applications. "Especially early on, the weight and the rolling resistance of them compared to a pneumatic tire, it's just not comparable," Bridgestone's director of consumer product strategy Will Robbins told us.

Robbins said that material advances are helping to reduce NPT weight, which is a major contributor to their high rolling resistance, but that noise and ride quality still need improvement. Despite the decades of research on NPTs, Robbins said they're still at the "infancy" stage compared to pneumatic tires.

Tire Treads and Retreads

The treads on today's higher-end tires are already significantly more advanced than those from just a few years ago. New patterns have fundamentally changed the way tires behave. "The thing that we've seen the industry do over the last decade that has been a game changer for us in terms of all season performance is what we call a 3D sipe," Bridgestone's Robbins said.

Sipes are the cuts you typically see most prominently in winter tires, designed to help the tread spread out to channel water and increase surface area. With 3D sipes, that pattern can be designed to interlock. "So when the tire is under free rolling or less strain, the sipes still open and close normally as it rolls through the footprint," Robbins said. "When you really start to put lateral or longitudinal load on it, they lock together."

That locking makes the tire feel and behave more like a stiffer, more summer-oriented tire in the dry while still offering winter performance that, according to Robbins, is "orders of magnitude" better than all-season tires of a decade ago.

What does that have to do with EVs? More drivers in states with real winters will be able to stick with all-season tires, which offer greater range than a dedicated, snowflake-rated snow tire. Snow tires have both a louder tread pattern and a higher rolling resistance than all-seasons. That means compromised range.

"You get all the stuff that helps make the tire quiet," Robbins said, "but also, when you put your foot down in something like a Mach-E GT, the tire locks together, and you still have a great amount of stiffness in the pattern."

In the future, the bigger changes may be the longevity of that tread. Right now, when the tread of a tire is worn down, the whole tire must be replaced (2/32 of an inch is the minimum depth in most states). In the future, the body of the tire may be able to be saved while only the tread is replaced.

Retreads are already the norm on trailer and industrial tires. "Big truck tires get retreaded three, four, sometimes five times," Robbins said. "The next phase of that from the consumer side is how do we bring that to the consumer market in a way that is relatable and safe and cost effective for the consumers?"

To be clear, consumer retreads are nothing new. It was a common practice through the first half of the 20th century but fell out of practice as more durable, longer-lasting belted tires came into favor.

Modern retreads will be a different beast, tires designed for easy refurbishment from the factory. That could reduce the cost of a new set of rubber by half and drop the amount of required materials by upward of 90 percent. The environmental benefits are clear, but there's a lot more potential on that front.

Environmental Impact

EV drivers tend to be a little more environmentally conscious than your average consumer, so manufacturers are increasingly focusing on creating tires that are themselves greener.

Most manufacturers are making major pledges, like Nokian building the industry's first carbon-neutral tire manufacturing plant in Romania, scheduled to open next year. Michelin, meanwhile, is aiming for full carbon neutrality in all its manufacturing by 2050.

But even if you can reuse the majority of the tire, the tread that wears off has to go somewhere. "Clearly, there's a significant amount of rubber that has essentially gone into the environment. And typically, that'll end up on the roads until the rain comes and washes the tire particulates into the ditch, into the water system, and eventually into our farmer's fields," Nokian's Bourassa said.

At present, a variety of organic compounds are used to create synthetic rubber, including butadiene—a toxic hydrocarbon derived from fossil fuels. In order to reduce reliance on those techniques, Michelin is beginning to extract similar compounds using biomass sources such as tree bark and even kudzu.

Additionally, a shift back to natural rubber may be part of the solution to reducing that fossil fuel dependency. Last year, Bridgestone invested $42 million into a facility to grow guayule, a desert shrub that could be a rich source of natural rubber. Early tires featuring this material are being deployed on IndyCar street circuits of all places, but in the future, alternate sources of raw materials like this will reduce the overall negative environmental impact of individual tires.

Likewise, Bridgestone's new Turanza EV all-season contains recycled carbon black from old tires, rice husk silica, soybean oil, and synthetic rubber made of recycled plastic bags and bottles.

Tire Compounds

More environmentally friendly compounds will be important in the future, but they'll still need to offer the right balance of grip, durability, and rolling resistance. A lot of that, Bridgestone's Robbins said, comes down to chemistry: "So the magic of what makes modern tread rubber compounds work is really how do you get polymers and silica to interact together?"

Silica is basically sand, which provides much of the durability and traction of a tire. The polymers, meanwhile, create the bonds that hold it all together and provide the overall dynamics of the tire. "The problem is, [silica] doesn't really want to bond with things, and especially these super-long polymer chains," Robbins said.

Lately, Bridgestone has been developing new mixing technologies that increase the amount of bonding. "I kind of liken it to making a cake with a hand mixer and a whisk. Or you can use a Kitchenaid that's gonna give you super-consistent results," Robbins said.

Bridgestone's new mixing techniques have already doubled the amount of silica-to-polymer bonding, but there's much more to come in this area of research. "What this new mixing technology allows us to do is continue to use more silica, then we need new polymers that are designed to take advantage of it," Robbins said. "Over the next decade, that's really where the continued research is going to be."

Tire Sensors

While all of the above should make for greater tires for all, when it comes to tires specifically designed for autonomous vehicles, the future is going to require a lot more information.

"Really, what it comes down to is sensors in the tires and what kind of information can we pick up about road conditions, grip levels, and then communicate that back to the driver," Nokian's Bourassa said. "And really, in this case the driver is a computer."

Why so much data? Think about all the nuanced ways we get feedback from tires, things like screeching sounds, steering wheel vibrations, and bulging sidewalls. An autonomous car won't necessarily be able to pick up on all that, so the tire is going to have to work harder to report its condition to the car.

"The unicorn in our industry for that is an intelligent tire, a tire that can provide input about its health to the vehicle, but also a tire that can provide input about available traction to the vehicle," Bridgesone's Robbins said. "There are ways, with tire-mounted sensors that we are working on combined with vehicle systems, to actually be able to tell the vehicle how much traction is available at any given moment."

Such sensors are beginning to appear in production tires, particularly in industrial applications, where they can report wear and temperature data and alert operators of problems ahead of potential accidents.

New sensors will require new ways of communicating that information. Nokian's Bourassa is hoping we don't get a repeat of what happened with the humble tire pressure monitoring system, or TPMS. "When that came into law, there were a few different sorts of systems that were used for it and made it a bit of a nightmare for dealers," he said. "I certainly hope that standards would come up and that would allow consumers to continue to have an option and a selection when they replace their tires, instead of having to purchase the OE tire only that was set up to communicate specifically with their vehicle."

Putting it All Together

So what might this future tire, full of sensors but devoid of air, actually look like?

The best preview might be Michelin's Vision concept tire, a sneak peek at how the brand envisions a tire of 2050. "The Vision concept is comprised of both a wheel and an airless tire," Michelin's Shepherd told us. "It is biosourced, connected, and features a renewable tread." That tread is actually 3D printed, so it can take advantage of shapes and geometries not available in the traditional molding process.

So, yes, it's retreadable, made of advanced compounds, is loaded with sensors, and is constructed of environmentally sound materials. It ticks all the boxes—and it also looks like something that fell off of an alien spaceship.

Will the tires of 2050 actually look this otherworldly? We won't know that for another 25 years or so, but for now we can at least take solace in knowing that, even then, they'll still be round.