There’s a lot of weird mystery around tires for EVs. Some people think a tire is a tire, and that EVs don’t need anything special. Other times, a tire shop might think that EV tires are so different that they won’t know what they’re doing, and thus refuse to even sell you tires. While I’ve read a fair amount about this topic and there’s a lot of internet lore, the truth of this topic could use a nice, easy-to-understand presentation. The good news? Jason at “Engineering Explained” does this every week, and this time he discussed EV tires!
He starts right at the beginning explaining why tires matter for EVs in ways they might not for gas-powered cars:
- The extra weight
- The need for efficiency (to get range)
- How quiet they are compared to ICE
- With the sudden, strong torque, even slower EVs punish tires.
So, we know, not even half a minute in, that the “tires are tires” theory isn’t where it’s at. An EV tire needs to handle the weight and torque, help the vehicle have better range, and not make so much noise that the people in the car are annoyed by it. And doing all of those things at the same time as providing needed safety and performance isn’t always easy.
In typical fashion, Jason goes into detail about each of these aspects of tire engineering, while making it all easy to understand.
As we all know, EVs tend to be heavier than similar gas-powered cars. It’s not always a huge difference, but on average, it’s true. No matter how you design the car and how structural you make the pack, the battery cells still have to weigh something. My Bolt EUV’s battery pack weighs in at 1,000 pounds, and some vehicles are even heavier to get more power and range.
The easy way out would be to make the tires wider, because that would spread the extra weight over a larger area. But, if you did that, you’d end up with a wider tire that fights the air more (lower aerodynamic efficiency). This would also add rolling resistance and other issues that rob range. Plus, the tire would wear out 20% faster. Ouch!
Instead of making the tire bigger to spread the weight out over a larger area, tire manufacturers make the tires stiffer to hold up under the weight. This has the added bonus of better handling and steering response, because the tires will be less squishy and sloppy.
But what about comfort? This normally would make the car rough and uncomfortable, but the extra weight of the EV balances out with the stiffness of the tire, making for a comfortable ride. So, it all works out in the end. It’s all about matching the tire to the vehicle it’s going to be mounted under.
Efficiency of Electric Car Tires
Tires do a lot of important jobs. They keep you from slipping and sliding all over the road, and nobody wants that. But that resistance to moving also makes it hard for the vehicle to move the way you want it to (rolling resistance). So, how do tire manufacturers give you the grip you need without holding you back and hurting range?
What it all comes down to is what kind of rubbery materials the tire is made of. These are marketed as “low rolling resistance” tires, but tire companies don’t want to tell you what the secret sauce is that went into making the tire because they want an edge over the competition. Hankook told him that their biggest challenge is having the tires get an even cure during the manufacturing process.
How Electric Car Tires Can Cut Noise
This is an area where EVs get to fight an unfair fight. Because their motors and electronics are relatively quiet, people riding in the car hear the tire noise more. So, to make the cars comfortable, you have to do something about that.
If you’ve ever gotten a Tesla a pair of tires, you may have seen the foam that some tires have inside them. That’s there to cut down on the tire noise by getting between the rubber and the metal wheels to help insulate you from the sound a bit. This alone could cut the sound almost in half.
Another key thing to quieting a tire down is the tread pattern. The most capable off-road tires tend to be very loud, so it’s not hard to see how other tread designs might do the opposite. The video goes into detail about how small shape differences could lead to big sound differences. The different sizes of tread blocks alone do a lot of the work without being apparent unless you gave a tire a close look (they’re not actually the same size to keep a rhythm from happening).
Electric Car Torque Tears Up Tires
All of the sudden torque that an electric car can produce is hard on tires. So, tire manufacturers have to do something to help improve that situation. It’s also related to the weight of the car, so EV tires can get a double whammy.
Once again, it comes down to rigidity. To get better grip and not get destroyed as quickly, tire manufacturers have to keep the tires from deforming as much under weight and fast rotation to stand a chance.
This Is An Emerging Field
Something that he didn’t get into in the video is how tire design for EVs has evolved. Before EVs burst onto the scene, the most efficient cars were often light and less powerful, making for an easier job on the tires. But, with the extra weight and performance of today’s EVs, all of that has been upended.
We shouldn’t expect 2022 tires to be the final say on the matter, and not by a long shot. Not only are tires still improving to be even better for EVs, but EVs are changing, too. On top of that, there are emerging technologies like airless tires that could upend it all again, opening up new design choices and allowing people to spend more on tread.
For now, though, don’t obsess too much about getting the perfect EV tire. It’s all about getting a tire that does what you need the vehicle to do.
Featured image: screenshot from Engineering Explained.
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