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但是即便(bian)使(shi)用了重載輪胎(tai)(tai)，電動車的額外重量(liang)和較高(gao)的瞬時扭矩仍會(hui)導(dao)致輪胎(tai)(tai)與路面之間的摩擦力增加。因此(ci)，許(xu)多電動車車主會(hui)發(fa)現(xian)其輪胎(tai)(tai)磨損得(de)更快，俄亥俄州阿克倫市全球材(cai)料科學與工程公司Smithers的咨詢(xun)業務副總裁Josh Guilliams告訴SAE。該公司在測試與協助(zhu)開發(fa)輪胎(tai)(tai)方面積累(lei)擁(yong)有超過99年(nian)的經驗(yan)。

To EV or not EV? It’s a question more and more motorists are asking as they look to purchase replacement tires for the electric vehicles that grace their garages. Should they buy special “EV tires,” or just look for good tires that fit their electron-gulping cars and light trucks? Tire engineers know it’s not a silly question and that OEMs have their work cut out for them on the education front. A 2023 Michelin survey found 83% of motorists, including half of all EV owners, didn’t understand the different tire needs of EVs and ICE cars and trucks.

EVs Are Different

A tire designed for an ICE sedan might work well on a comparable EV, but chances are that unless specifically designed to be especially quiet, energy efficient, or to carry heavier-than normal loads, it likely will disappoint in terms of tread life and perhaps other characteristics such as noise.

EVs can easily be 20-30% heavier than similarly sized ICE vehicles. Safely supporting and managing that extra weight requires a tire with a high load rating. In fact, the “High Load” (HL) designation was developed in 2021 in response to the growth of EVs in the market as a way to signal a tire with higher load capacity than one built to the former XL standard, when inflated to the same pressure.

Even so, an EV’s extra weight and instant torque create higher levels of friction where the rubber meets the road. The result is that many EV drivers find their tires wear out faster, Josh Guilliams vice president of consultancy for Smithers, a global materials science and engineering company based in Akron, Ohio, told SAE Media. Smithers has been testing and helping develop tires for more than 99 years.

While a quality set of “normal” long-wearing passenger car tires might last for up to 60,000 miles, an equivalently sized EV’s tires might need replacement after as little as 30,000 miles. Drivers of sporty EVs with lots of horsepower and torque might be lucky to see 10,000 miles out of a set of tires, Guilliams said.

Increased cabin noise is also a potential issue. Without the benefit of an ICE to mask high-frequency tire and wind noise, EV makers have had to step up their game in cabin soundproofing, enlisting tire makers to design ever-quieter tires to help keep cabins peaceful.

Finally, fuel efficiency is important to most EV drivers, which drives demand for tires with low rolling resistance since reduced friction between the tire and the road increases an EV’s ability to eke more distance out of every watt of energy in its battery pack.

Adapting to EVs

Tire makers point out that work on many improvements that benefit EVs, especially in noise suppression and efficiency, started long before plugging in modern cars was a thing. The advent of luxury SUVs whose large cabins tended to amplify road noise fostered the first efforts for quieter tires, Russell Shepherd, technical communications director for Michelin North America Inc., in Greenville, South Carolina, told SAE Media. And it was federal fuel efficiency regulations, which began long before the advent of EVs, that began the drive to develop tires with lower rolling resistance, Tracey Norberg, senior vice president and general counsel for the U.S. Tire Manufacturers Association, told SAE Media.

The arrival and growth of electric vehicles in the market pushed tire makers to speed up the development of techniques and technologies that benefit both EVs and ICE vehicles. Chief among them are the introduction of sound-deadening foam blocks or strips inside tire cavities to help reduce tire noise. The specially designed foam pieces can reduce air resonance, which finds its way into the passenger cabin as noise, by as much as 50%, Dave Zanzig, senior director of consumer tire technology and new tire development at Goodyear Tire & Rubber Co., in Akron, told SAE Media. Other techniques include new (and generally proprietary) rubber compounds to improve tread life, rolling efficiency and traction, and tire tread designs aimed at improving wet weather handling and noise reduction, especially in tires made with harder compounds to maximize tread wear. Advancements in synthetic elastomer compounds have provided “enhancements in terms of traction, rolling resistance and wear balance,” Guilliams said.

The industry also developed High Load or “HL” tires to handle higher air pressure, which provides more weight-bearing capacity, without increasing in size. HL tires are used on vehicles heavier than the SUVs and vans for which the decades-old XL – Extra Load – rating was developed.

Compared with a standard load (SL) tire with a 32 psi pressure rating, the same-sized XL and HL tires might be rated for 42 PSI. While an XL tire with a load index of 94 can carry just under 1,500 pounds (680 kg), a same-sized HL-rated tire gets a load rating of 98 and can carry just over 1,600 pounds (726 kg). An HL tire has more rugged construction, especially in the sidewalls, to handle the weight of hefty EVs such as the newly introduced Volkswagen ID.Buzz, which tips the scales at just over three tons in its dual motor,  all-wheel drive configuration.

HL tires are important to automakers because the alternative – going to bigger wheels and tires – adds even more weight and often requires larger wheel well capacity. That can eat into energy efficiency as well as valuable cargo and passenger cabin space, making that EV less competitive.

Weighing Tradeoffs

Developing tires, for any type of vehicle, is “a game of checks and balances,” Joshua Sortor, product and quality director for Discount Tire, told SAE Media. The Arizona company also owns the America’s Tire chain, the online retailer Tire Rack, and the highly regarded Treadwell tire testing, evaluation and recommendation tool.

“Once you meet the load rating, it comes down to what it is you are looking for in the tire. A lot of EV owners want a quiet tire that’s very efficient, but efficiency generally sacrifices lifespan, and it’s also harder to get good winter and wet performance with a high-efficiency tire,” Sortor said.

Michelin’s family of Primacy tires, for instance, includes a line called the e.Primacy aimed at EV and hybrid owners as well as at motorists seeking maximum tread life. The ICE-oriented Primacy 4 is designed for traction and gets an “A” rating for wet grip and a “B” rating for rolling resistance. A same-size e.Primacy, designed for long tread life, gets an “A” for rolling resistance but a “B” for wet grip.

E – It’s Also for Eco-Friendly

Some tire makers also have seized on the notion that EV buyers are particularly environmentally conscious and have made sustainability a feature of tires aimed at electric and hybrid vehicle owners.

Goodyear is among those developing sustainable materials. In collaboration with suppliers and universities, the company developed a method of extracting silica, a key ingredient in tire compounds that improves wear and traction, from ashes of rice husks that are often burned by the millions of tons to generate electricity worldwide. As a result, Goodyear has reduced its consumption of the world’s declining sand reserves – approximately 40% of a tire’s weight is silica – and the silica-laden husks aren’t going into landfills. Goodyear also “uses soybean oil instead of petroleum oil and is making advanced polymers from biomass,” Zanzig said. The company’s ElectricDrive 2, a tire aimed at EV owners, “has 50% sustainable content,” he said.

The Cost Factor

One drawback to EV tires is that they can cost as much as 20% more than comparable tires without EV-specific features. The higher cost is a function of their unique materials, more rugged construction and low-volume sales, which makes it harder for manufacturers to recoup R&D, materials and marketing costs without increasing prices, said Bob Liu, research and development director for passenger cars and light trucks at Continental Tire the Americas in Fort Mill, South Carolina.

PR or Substance?

Goodyear ’s Zanzig maintains there is real technology behind EV labeling, that it’s not just PR. Continental ’s Liu, on the other hand, said that EV-labeled tires “are more focused on marketing than performance” and that “competition, not EVs, is driving tire improvements.” Both Goodyear and Continental belong to the U.S. Tire Manufacturers Association, which takes the stand that, special label or not, a properly sized tire that meets or exceeds the vehicle manufacturer’s specifications can function on both EVs and ICE vehicles. While a tire doesn’t have to be labeled “EV” to be an EV tire, such labeling can help consumers, said Discount Tire’s Sortor.

In general, EV-specific tires such as the Electric Drive 2, Yokohama’s recently introduced Advan Sport EV A/S, Bridgestone’s Turanza EV, Pirelli’s P Zero AS Plus Elect and Michelin’s e.Primacy are designed to favor attributes such as quietness, long tread life and fuel efficiency.

Tires are designed to prioritize specific goals, which leads to many varieties, Drew Dayton, senior product planning manager for consumer tires at Yokohama Tire Corp, North America, in Santa Ana, California, told SAE Media. He’s of the same school as Continental’s Liu, holding that all properly fit tires are suitable for either EV and ICE use. Even so, the company does make the Advan Sport EV line, designed for maximum tread life with “acceptable levels of handling, rolling resistance and noise.”

So, EV or Not?

The consensus among tire makers, backed up by findings from Discount Tire’s testing program, is that a tire is only as good as its load, speed, wear and weather and terrain ratings. When those things match or exceed the vehicle OEM’s tire requirements – usually posted on a label fixed to the driver’s side door jamb or the inside of the glovebox door – it shouldn’t matter whether the sidewall says anything about EVs or not. But tires specifically designed for EVs can offer electric vehicle owners additional benefits.

“There is definitely a need for tires that are customized to support the unique performance attributes of EVs,” Guilliams said, noting that tire makers have invested “significant resources” into developing tread formulations to extend an EV tire’s life without sacrificing grip or rolling resistance.

“There’s real technology fueling the innovation behind optimizing tire performance for electric vehicles,” Zanzig said.