HANOVER, Germany — As the electrification of vehicles continues to make strides during the next decade, there will be a significant impact on the design and production of tires.
That's the conclusion researchers from Smithers Rapra came away with in doing a research on "The Impact of Electric Vehicles on Tires to YR2028," a paper presented by Bruce Lambillotte, vice president of technical consulting, during the recent Tire Technology Expo 2019 in Hanover.
Range, vehicle torque and noise will be the key tire performance parameters affected by the growth of electric vehicles (EVs) , Mr. Lambillotte said during an interview at the expo.
Smithers Rapra forecasts that sales of EVsehicles will rise roughly nine-fold by 2028 to nearly 45 million from fewer than 5 million new registrations worldwide in 2018. The Smithers vice president said these sales estimates cover all types of EVs, including full battery, hybrids, mild hybrids, plug-in hybrids and fuel cell hybrid vehicles.
The testing and consulting firm projects that over this period, battery EVs will account for about half of all EVs sold, and the battery types — including models such as the Tesla and Nissan Leaf — also likely will have the most impact on tires.
Mr. Lambillotte said battery EVs can be characterized in a number of ways, one being that they're typically heavier and also limited in traveling range.
"It does not have the backup of an internal combustion engine within the same vehicle like some of the hybrids do," he said. "So it has range limitations. There has been some good battery evolutionary changes over the years, but still its range may be as much as 40 percent less as the range of an internal combustion engine vehicle."
Because of this, the tire needs to provide good fuel economy, which means low rolling resistance, Mr. Lambillotte said, adding that tires for EVs may need to be as much as 20 percent or more improved in terms of fuel economy than for today's traditional vehicles.
"Normally we think of OE tires as needing rolling resistance to meet regulated demands, such as CAFE standards in the U.S. or in Europe for tire labeling, especially in the replacement market," he said. "For here we're talking for a different reason: First and foremost for range."
From a tread compound perspective, that typically has meant higher use of silica to boost rolling resistance, but Mr. Lambillotte said much of the advantage from that aspect probably already has been achieved.
There could be other changes that could improve rolling resistance, such as the height mass spec ratio of the tire.
"A tall tire tends to have better rolling resistance, especially if it is a narrower cross section," he said. "And indeed one Tier I tire company is looking in that direction of modifying the outside dimensions of the tire aimed at improving rolling resistance above and beyond high silica, low rolling resistance treads."
Torque, noise issues
Battery EVs deliver what is described as rapid or instantaneous torque, a condition that will require that tires be able to sustain their performance with improved dry and wet traction capabilities, Mr. Lambillotte said.
"It's something that requires refinement from both tire engineering and tire compounding in the tread areas."
Regarding noise, battery-powered EVs are extremely quiet.
"Whereas tire noise is a smaller percentage of total noise in an internal combustion engine vehicle, if you take away that engine noise, then the tire noise is more easily perceived and is a bigger percentage of the total sound being emanated," he said.
It is estimated that tires for battery EVs may need to be as much as 30-percent lower in noise generation, he said. There has been a good deal of work to reduce nose for traditional engines, and some of that can be transferred for use in EVs.
One area of work for noise cancellation involves putting foam components inside the tire cavity to absorb noise.
"This may be an area where we'll see revolutionary change," Mr. Lambillotte said. "Perhaps we're already seeing this revolutionary change in terms of additional materials used inside the cavity of the tire."
During the period, Smithers Rapra is expecting 26-percent compounded annual growth for EVs, particularly as more public power changing stations are put into service. To date, he said it's been somewhat of a vicious circle, with not enough EVs on the road to justify the investment in charging stations and the lack of charging stations hampering the growth of EVs.
Typical charge times can range from roughly 30 minutes on a supercharger to as much as eight hours for home charging stations.
While both Europe and the U.S. are starting to get more infrastructure, it's clear that China will be the leader in EV growth, he said.
The Chinese government is heavily supporting the development of EV technology, and is putting most of its resources behind battery EVs. With China promoting that type, it's estimated battery EVs already represent as much as 79 percent of all EVs in China, according to the report.
The reasons are two-fold, the Smithers Rapra research shows. One is that battery EVs will reduce the urban pollution issues that have challenged China over the past several years, and the other is the government believes it will help reduce China's dependence on foreign oil.
Smithers Rapra predicted that new EV registrations in China will jump to about 19 million in 2028 from a couple of million in 2018.
The next largest growth area likely will be Europe, going to about 13 million in 2028 from fewer than 2 million last year. The U.S. will be third, climbing to slightly over 5 million units in 2028 from about 350,000 units.
Mr. Lambillotte said there are several factors that will keep U.S. growth of EVs well below that of China and Europe.
"A special challenge to accelerating growth in the U.S. is the fact that the American consumer tends to want more range than the Chinese or European consumer, and indeed in many cases for good reason," he said.
The factors that will lead to growth in all areas is that consumers will have more options in terms of the variety of EV modes for sale, and access to more charing stations.