Where The Rubber Meets The Road For Electric Cars

JOHN DANKOSKY: This is Science Friday. I’m John Dankosky.

DIANA PLASKER: And I’m Diana Plasker. There’s an expression, where the rubber meets the road. It’s that important point at which an idea gets put to a practical test. Your tires certainly are an important practical point, but you might not give them much thought until you get a flat.

But as more people in the US make the switch to Electric Vehicles, some are finding they have to think about their tires more seriously and more often. Some EV drivers are finding their tires are wearing out more rapidly than when they were driving traditional internal combustion vehicles. So what’s going on? Joining me now to talk about where the rubber meets the road is Ryan Pszczolkowski. He is the tire testing program manager at Consumer Reports. Welcome to Science Friday.

RYAN PSZCZOLKOWSKI: Thank you, Diana.

DIANA PLASKER: All right, first off, I don’t think all that much about tires living in New York City. But there’s a lot more to tires than getting the right size and pressure. Is that right?

RYAN PSZCZOLKOWSKI: You’re not alone. A lot of people don’t think about their tires much. But yeah. Tires are highly engineered. Pretty amazing products, actually. And you said it earlier, where the rubber meets the road. I mean, a vehicle goes down the road, and there’s only four things touching the road. And those are the four tires underneath that car. So they are very important in keeping that car safe and getting you where you need to go.

DIANA PLASKER: And with electric vehicles, some people are finding that their tires are wearing out faster than they’d expected. What’s going on there?

RYAN PSZCZOLKOWSKI: Yeah, it’s a real thing. And it’s kind of taken the car world by storm right now. Your electric vehicles are heavier than your regular internal combustion engine cars. In some cases, 10%, 20%, even up to 30% heavier than the internal combustion engine that we’re used to. So that’s considerable.

And what we were seeing is, roughly, tires wearing out 20% faster than they would on those regular vehicles, those internal combustion cars. And that’s kind of frustrating because tires in general are expensive. But a lot of these EVs, they’re putting them on a bigger wheel, lower aspect ratios sidewalls. And tires like that are more expensive in general anyway. So these tires are expensive. And now you have to replace them, in some cases, almost twice as much maybe depending on how you drive, where you drive, and what you drive. So it’s becoming a glaring obstacle for people with EVs.

DIANA PLASKER: So you said they’re wearing out about 20% faster than traditional car tires. How does that shake out in terms of numbers of miles? What are we talking here?

RYAN PSZCZOLKOWSKI: Yeah, so just some anecdotes here from the track. We have a whole fleet of cars. And we’ve got about 22 or 23 EVs here. And we wear tires a little quicker because we are testing them. We’re putting them through their paces here at the track. But we’re seeing some tires on a traditional car might last us 25,000 miles. Some of these EVs, we’re wearing them out in 12,000 miles.

DIANA PLASKER: Wow. And so why are they wearing out faster? What’s special about EVs?

RYAN PSZCZOLKOWSKI: There’s two major factors. The number one factor is the load, the weight. As you put more weight on a tire, it’s going to wear out faster. And as I mentioned before, some of these EVs are almost 30% heavier than their counterparts. So that’s a lot of extra weight.

That combined with the torque. An electric motor has almost instant torque. And different manufacturers are designing the vehicles in different ways where they apply that at a different rate, if you will. Some of these cars will basically snap your neck as you accelerate. And that’s fun, but you’re literally leaving a strip of rubber behind the car without actually spinning the tire, if you will.

So it’s kind of a neat phenomenon. If you watch one of these EVs take off on a road quickly, it’s not doing a burnout, if you will. But you can actually see the rubber scrubbing off onto the asphalt.

Another phenomenon with EVs is they have what we call regenerative braking. Basically, as you lift off the gas pedal, and the car will slow down right with that. So you’re not even reaching for the brake pedal. So what’s happening is you’re now– now you’re creating a force back in the other direction, and you’re scrubbing rubber again, as if you were accelerating, but in reverse, if you will. And that happening all the time as you’re driving, it adds up.

DIANA PLASKER: So it sounds like you’re saying that the problem isn’t necessarily the tires themselves but really the conditions they’re being subjected to. So if I, for instance, made a lighter electric car that didn’t accelerate as fast, would at least part of this problem go away?

RYAN PSZCZOLKOWSKI: Sure, that would certainly help. And still, tires are a compromise. If you want to make a tire last longer treadwear-wise, you might be pulling away from its wet grip or snow traction. It’s all a compromise. And you can’t have it all, if you will. So there’s a balance of where do you draw the line in terms of performance, in what direction.

So for instance, we have a Tesla Plaid. And it has these ultra-high-performance summer tires on it, basically. These tires in general, even not on a Tesla or an electric vehicle, or wear out quicker because they’re designed to grip the road in dry and wet conditions and handle. So they wear out as it is quickly. So they have a soft compound. Now you put them on a Tesla and add all that weight and the power, and you’re just going to melt them off even quicker, if you will.

DIANA PLASKER: So besides having to hold more weight, are there other specific properties you want in an EV tire?

RYAN PSZCZOLKOWSKI: Yeah, absolutely. So the other big thing, in some cases, people are even more concerned about, is rolling resistance, which is the tire’s ability to roll along the ground. So a tire with lower rolling resistance requires less energy to roll. Now, an internal combustion engine car, the vehicle itself is only about 25% efficient. And only 5% of that efficiency is affected by the tires.

An EV drive train is about 80% efficient, which now makes the tires a much greater part of that pie. 16% of the efficiency of the vehicle comes from the tires now. So the tires are now more in the spotlight, if you will, because they need to keep up with those ranges that they’re claiming that these vehicles get.

The other one that people don’t quite think about, but if you’ve been in an EV, you’ll realize right away how quiet the car is because there’s no mechanical sounds. You really only hear wind and some road noise. So what they’re finding is they’re actually building tires for EVs that have acoustic foam inside of them to keep cavity noise down. So as you drive across rough surfaces, the tire can create a noise that can come into the cabin. So they’re combating that as well.

But again, that’s not a performance or an efficiency thing. So it’s a little bit less thought about, if you will. But it is something that they’re considering.

DIANA PLASKER: So as the tires wear down, the rubber doesn’t simply go away. It sticks around on our surfaces, our air, even our oceans, as microplastics. So what about the environmental factors?

RYAN PSZCZOLKOWSKI: Yeah. I recently was at a tire conference. And there was a lot of talk about tire particulate. And this has been happening even before EVs. But as the tire wears out, the rubber goes somewhere. It comes off in maybe a very small dust, or a particle, or, in some cases, bigger chunks. It goes somewhere. It’s on the sides of the roads. It’s in the air. It’s everywhere.

But as EVs come out, now these tires are literally– I keep saying melting. They’re wearing these tires out so fast. It’s kind of come into the spotlight. Hey, where is this rubber going? And is it bad? Does it go away eventually? What does it do?

There’s not a whole lot of information on it yet. This is a sort of a new thing that we’re really starting to focus on. Europe’s a little bit ahead of us. They are proposing some testing to figure out, how can we measure this stuff? And how can we test it to see how bad it is? And a tire is– a rubber compound has a lot of different polymers and lots of things in it. So I can’t imagine it’s wonderful for you.

DIANA PLASKER: Yeah. So what’s the solution here? Is this something that EV owners are just going to have to accept, that they might not have to take their car in for oil changes, but they’re just going to have to replace tires more often? Or is there another solution that you’re hoping we might see?

RYAN PSZCZOLKOWSKI: Well, right now, they’re going to wear out tires faster. You can drive a little more gently, if you will. But you can’t get rid of the load. The battery is the battery. The vehicle is the vehicle. You got to put people in it, and you got to put stuff in it and go. So you can’t really change the load. But you can drive a little bit more gently, accelerate and brake a little easier. That can help.

But I foresee some technology coming along where they’re going to be able to make these tires last longer, still provide you with the grip you need for all seasons. Tires have come a long way in the last 18 years I’ve been here. And it just keeps getting better and better. It’s just going to take time.

DIANA PLASKER: Ryan Pszczolkowski is the tire testing program manager at Consumer Reports. Thank you so much for joining us today.

RYAN PSZCZOLKOWSKI: Thank you very much.

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