The Pros and Cons of Various EV Tires (Performance vs. Efficiency)
It's no secret that the majority of electric vehicles available today are used for more than just getting about. EVs of today are frequently sporty, quick, and enjoyable. That's fantastic for those of us who enjoy driving, but it can make picking the correct tire more challenging. Why? due to the EV range, tire grip, and tire wear's inherent conflicting interests.
Yes, it is true that even electric vehicles are governed by physics. Others contend that EVs incur a larger physics cost than their internal combustion engine (ICE) equivalents due to their greater low-speed torque and heavier weight. Fortunately, tire makers are attempting to reduce the cost that physics makes us pay to create the grip necessary to have it both ways, which is good news for EV owners who value both maximum pleasure and optimal range. To understand more about the advantages and disadvantages of different EV tires and how that could change in the near future, we recently met with a group of Michelin specialists.
How Much Does It Really Matter?
Knowing that you must sacrifice some economy or range in order to improve traction or wear performance—whether on or off the road, or in rainy or snowy conditions—is one thing, but how much does it really matter?
According to Michelin product manager Steve Calder, "if I start with a tire that is optimized for range homologated for an OE [original equipment] EV car, something along the lines of our MICHELIN® PrimacyTM family of tires, that would be our greatest range offer." Now, if you go to something like our MICHELIN® Defender® tire, where we substantially compromise on the wear element and change the balance, what we would anticipate in terms of a reduction in range between the PrimacyTM and the Defender® is on the wear side.
Even while it might not seem like much, if you use a 2022 Tesla Model X as an example, 9 percent of its 348-mile EPA-rated range would represent a loss of 31 miles. When comparing brand-new, unworn tires, that might not be a deal breaker for some people, but for others it could mean an additional charging stop—or more.
The difference might be much bigger, up to 15% or more, when comparing the benefits you might see when switching from old tires meant for extended wear or high performance to new tires designed for maximum range.
Going straight to a new tire from a worn tire in the exact same tire type has astonished consumers and even dealers, according to Calder. "Between the time the tire is new and the time it reaches the end of its useful life, the range may fluctuate by roughly 6%. Therefore, there is a compound effect when a customer goes from a worn-out tire that is tuned for range to a brand-new tire that is tuned for wear. Consequently, you end up with a range effect of more than 10% when you combine the, say, 6 to 9 percent hit from the different tire model with perhaps a 6 percent hit from the worn-out tire."
For our fictitious 2022 Tesla Model X, a 15% reduction in range would result in a change of more over 50 miles. It's important to note that these variations result from contrasting Michelin's own tires with one another. The variations may potentially be more pronounced when comparing brands.
According to Russell Shepherd, head of technical communications at Michelin, "If you take the European [standard], they include rolling resistance as part of their grading; it's on the label of the tire." And there is an about 15% variation in range between tires with ratings of A (the best rating for rolling resistance) and D (poor performance for rolling resistance).
How much, therefore, do various EV tire kinds matter? It turns out quite a deal, particularly in terms of range.
The Science Of Grip, Wear, And Range
It may seem odd that a tire with extended life wear characteristics would be less effective; after all, if it doesn't wear out, it can't have much rolling resistance, can it? Although it might seem to make logic, the contrary is true.
So the tire loses energy, which is why you have this range problem, Shepherd explained. "A tire loses energy due of deformation when it enters the contact patch. Although it is more comfortable as a consequence, energy is lost due to the distortion. The simplest way to extend the wear life of a tire without any technology is to simply add additional rubber, especially in the tread region. But when more rubber deforms, there is an increase in energy loss.
Perhaps counterintuitive, but when put that way, it all makes sense, right? But what if you made the tread compound more wear-resistant rather than adding additional rubber?
Actually, Calder stated, "That's another one that customers confuse or think is something else." "In fact, before I started working at Michelin, I was unquestionably one of these folks. However, I believe the general consensus is that a very hard rubber compound is preferable to a very soft rubber compound for rolling resistance. The greatest rubber compositions for rolling resistance are really the soft ones."
Hold the telephone! How are softer tires better at reducing rolling resistance than harsher tires? As previously stated, the majority of a tire's energy loss is determined by the flex of the tire carcass at the contact patch, and a softer compound will bend more easily, meaning less energy is lost.
Noise: An EV-Specific Issue
Tire noise, or cavity noise as it is known in the industry, is one issue that performance EVs face particularly difficulty. Tires generally create some noise. That is just the nature of an air volume contained within a deformable membrane; consider a drum. However, in an EV, the repetitive hum of its high-grip tires is not drowned out by a loud, boisterous V-8 or a throaty, turbocharged four-cylinder. What then should a tire manufacturer do?
Shepherd remarked, "You know, the fascinating thing is that we all know [electric] vehicles grew quieter. Internal combustion engines don't exist. And if you truly want to be economical, you remove the sound deadening because it adds weight; as a result, you will unavoidably hear more tire and road noise. more tire rumble But for years, we've been optimizing for that. We refine the chemicals in our tread. For that, we have design guidelines, and we really optimize the block size. The blocks aren't all the same size, much like when you look at a Michelin tire. Though it appears random, all of it is done to account for noise.
It's not at all unusual to see tire makers adjust the shape and size of the tread blocks to enhance grip, water handling capacity, and wear, so it probably shouldn't come as a surprise that the acoustics of a tire may also be adjusted.
Shepherd remarked, "If I'm going to play the specific tread blocks, I could play it [as if it's] a piano note. "I can alternate between two, three, or four notes, which is less unpleasant than playing the same note again. I can also play the same note repeatedly. That is what we do, then."
Similar to how musicians add foam to studio walls, tire manufacturers like Michelin add foam to the internal surface of tires to further dampen cavity noise.
However, not every vehicle or driver will require all of these noise-damping innovations. For one example, the kind of road surface has a significant impact on tire and road noise, therefore drivers in regions with more concrete highways/freeways or rougher surface patterns will hear more noise than those in regions with smoother roads. Similar to this, even on the same routes, certain vehicles may require acoustic foam in the tires while others may not. Shepherd remarked, "But our acoustic foam isn't exclusive. "We apply it at manufacturers' request if there is an obtrusive [frequency] range throughout their development."
The Bottom Line
No matter which tires you pick, you cannot have the best of all worlds in terms of grip, wear, efficiency, and noise. There will always be trade-offs, whether required by the rules of physics or simply by the wants of the customer. As EVs become more common in the market and, eventually, more inexpensive, those trade-offs will become even more significant to more drivers. However, a large number of tires are already available on the market that maximizes one, two, or all three of these countervailing factors, so EV enthusiasts already have a large selection of tires to choose from, even if they do have to give up some range, wear or noise in order to achieve the best performance.