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If you've been keeping up with our electric vehicle tires series, you know that there are some special concerns when it comes to choosing the best tires for an EV—issues like wear, noise, and efficiency are even more significant than with internal combustion engine (ICE) vehicles.
It won't surprise you then to learn that there are special considerations for winter tires when it comes to EVs, too. Fortunately, Michelin winter tire product category manager Farell Scott spoke with us recently to explain what goes into making and choosing the best winter tires for EVs.
What Makes An Electric Vehicle Winter Tire Different?
A winter tire for a standard ICE vehicle first and foremost needs to provide potent grip during icy and snowy conditions. Secondarily, tire noise levels need to be mitigated as much as possible and the tires also need to offer reasonably long life. "Winter is about more than just temperatures; snow, slush, ice, rain, your tires will ultimately need to be able to deliver performance on those different surfaces," Michelin's Scott said. "That increased level of traction in those conditions is really what separates a winter tire from an all-season."
A winter tire for an EV needs to do those same things—but it needs to do them in different operating conditions, even when facing identical weather. How so? The EV's winter tire will have to brake and turn more weight, all else being equal, and also handle the higher low-end torque of an EV when starting from a stop. The EV also doesn't have a noisy, vibrating engine masking the sound the winter tire's tread makes on the road, so the tire's noise design is even more important. And then there's the issue of range, which is compounded by the fact that EVs have a tendency to lose range in cold weather, due to reduced battery capacity, increased heater usage, a change in rolling resistance after tire changes and as the tires wear, or a combination of all three.
So while a good ICE winter tire has to do all of these things well, a good EV winter tire must do them even better.
What Makes A Good EV Winter Tire?
"Four really key aspects of what we've seen and heard that are important to EV customers, and also how we've approached our portfolio, are traction, noise, rolling resistance, and wear," Scott said. Traction makes sense for a winter tire, of course, and EV winter tires do this the same way ICE winter tires do, not just through compound, but also: through sculpture.
Sculpture? Yes, that's what the tire industry calls the design of the shape of the tire, including tread block size and shape. For winter tires, the tread blocks include lots of tiny cutaways called sipes. These sipes increase grip by providing another biting edge to the tire, but they also (along with the overall winter tire design) create more void area in the tread surface, too. Greater void area means more rain- and snow-clearing ability, but it also means less rubber on the road. That's where the tire's compound comes in.
"With the contact patch, where the road and the tire surface come in contact, it's the compound that's really the difference in the winter versus the all-season and summer products," Scott said. "It's the compound that obviously allows it to be able to operate in a cold temperature, maintaining its flexibility, which improves the traction on surface road."
Maintaining that flexibility in cold temperatures also helps maintain efficiency, as a tire that flexes easily wastes less energy to rolling resistance. But with less rubber on the road and a more flexible tire compound, it's also important to keep wear in mind, especially with EVs, which tend to wear out their tires around 20 percent faster than ICE vehicles, according to Scott.
"A tire that has full-depth features and has that performance over time is also very, very key," Scott said about mitigating the wear factor. "Because if you're consuming a tire that much faster due to EV torque and additional weight due to the batteries, then you'll start to see a drop-off in performance much sooner if you don't have tires that are built to have that performance over time."
Finally, noise handling is perhaps as important as the rest, because drivers won't tolerate a tire that performs well but makes excessive noise. Winter tires are, by their nature, noisier than non winter tires, and given that EVs are naturally quieter than their ICE counterparts, that's an even greater concern. So how does Michelin tackle the EV winter tire noise issue? With piano tuning.
Not actual piano tuning, of course, but Michelin's PIANO noise reduction technology, which involves tuning the shape of the tread blocks and tire grooves to tune out unwanted frequencies from the tire's noise profile. As with other Michelin tires, foam inside the tire cavity may also be used to help combat unwanted noise.
"So we have some technology that is Michelin proprietary, because we work with vehicle manufacturers, that's called acoustic PIANO tuning technology that allows us to really deliver tires that have optimal levels of noise reduction," Scott said. "Really that's been a key advantage for us, and this technology is something that is clearly implemented to deliver that level of low noise producing performance of our tires."
Choosing The Right EV Winter Tire
When it comes to choosing the right EV winter tire for you and your car, the process isn't all that different from choosing a good EV tire for the rest of the year or choosing a winter tire for any vehicle, whether it's an EV, ICE, or hybrid.
First, you'll want to figure out what your priorities are, since as with all things in life, the attributes of any given tire are often an exercise in carefully balanced trade-offs: More wear life may mean less traction or potentially less efficiency. On the other hand, more traction may reduce efficiency or wear. Noise can vary widely, seemingly independent of other considerations. So as with the choice of which EV tire to buy, the choice of which winter tire is right for your electric vehicle will also come down to your personal needs and preferences.
For Michelin, wear and traction and noise and efficiency are all important considerations, and it's the balance between them that matters, while always remembering that the single most important attribute of a winter tire—especially in tricky winter weather—is grip.
"We've tried to make sure that we found the right balance of delivering high traction, high grip-level tires in winter," Scott said. "So again, between the compound, between the sculpture, and between the siping and the voids that we've created on a tire with our contact patch, we try to maximize the grip level."