What is different about the tires on an EV?

Electric cars are just like regular, gas cars -- right?

Well, mostly.

One big difference often goes overlooked: EV tires. It turns out, tires are the only thing you have between you and the road. Whether you're looking for efficiency, a quiet ride, or curve-hugging excitement, picking the right EV-specific tire can actually make a big difference.

David Reese, Vice President, Americas Product Development at The Goodyear Tire & Rubber Company explains the nuance:

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The added weight and torque associated with EVs can impact several factors when it comes to tire performance, most importantly, load capacity, treadwear and vehicle range. In addition, noise from the road is often more noticeable when considering the quiet ride usually found with EVs. It is important to select tires that are equipped for the demanding needs of electric vehicles and balance the performance requirements desired from a growing audience of adopters.

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Read on to learn more about the main factors that matter when it comes to electric car tires.

Rolling resistance‍

If you're curious how tires affect your EV's efficiency, look no further than rolling resistance. So, what's this science-y term all about?

Tires are the bridge between your car and the road, and wherever they meet, there's bound to be some friction between the rubber and the pavement. This friction saps energy – the very energy that should be propelling your vehicle forward. While all vehicles experience tire friction, or rolling resistance, it plays a significantly more pronounced role in EVs due to the exceptional efficiency of electric motors. According to Russell Shepherd, a technical communications director for Michelin,

Tires eat up about 5 percent of the energy an ICE vehicle generates. But in the more streamlined EV drivetrain, tires consume about 16 percent.

Since rolling resistance has such a big effect on efficiency, optimizing it can have a big impact on your range. The proprietary material and shapes that many EV tire makers develop are closely guarded industry secrets.

The remedy for rolling resistance involves lowering the friction between the tire and the road. However, veering too far in the direction of reduced friction can compromise the car's grip on the road, potentially leading to skidding, sliding, or even spinning out. This concern becomes especially prominent during the rapid acceleration ("flooring it") that adds excitement to EV driving. Each car manufacturer and driver have the flexibility to choose tires that emphasize either traction or range. For instance, performance-oriented EVs designed for speed usually come equipped with tires that offer more rolling resistance, enabling drivers to unleash their speed demons. In contrast, more pragmatic EVs might prioritize minimal rolling resistance in order to extend their driving range.

Torque

Speaking of fast acceleration, we come to torque. This is what generally makes cars “fun to drive.” It’s certainly what makes EV drivers want to floor it at every stop light. 

Torque, the rotational force generated by a motor (or engine in traditional cars), is the magic that goes into turning the tires and propelling the car forward. The secret sauce here is that greater torque equals swifter acceleration. In internal combustion engines, maximum torque only happens when you hit a specific RPM (rotations per minute), meaning you need to hit a sweet spot to revel in the torque's power. On the other hand, electric vehicles feature just a single gear and a lot fewer mechanical components to impede the transfer of electric energy to the wheels. While we're skimming over some intricate technicalities, the bottom line is this: EVs can deliver maximum torque straight from a standstill, whereas ICE vehicles need to rev up to attain that optimal RPM.

If you've ever floored the accelerator in an EV, chances are you're already familiar with what we're getting at.

This zero RPM torque imparts a lively and zippy sensation to the car's movement, particularly at lower speeds, making the driving experience more thrilling than many new drivers imagine. It's no surprise, then, that regularly hitting the accelerator in your EV can lead to accelerated wear and tear on your tires, all thanks to the magic of torque. To counteract the additional wear and tear from the extra torque, EV tires tend to be crafted from more robust materials compared to those designed for combustion engine vehicles.

P.S. - The same principles come into play when considering the "reverse torque" your wheels encounter during regenerative braking maneuvers.

Weight‍

EVs are far heavier than their ICE counterparts (at least 10%). As the vital link between the car's body and the road, tires inevitably shoulder the impact of any additional weight.

An obvious option to distribute this extra weight involves broader tires, but this introduces increased air resistance, ultimately compromising the vehicle's efficiency. Instead, many EVs are outfitted with "heavy-duty" tires crafted from exceptionally rigid materials. Since they are more rigid, these tires necessitate significantly higher air pressure compared to their counterparts on ICE vehicles.

I still remember my surprise when I first inspected the tire pressure on a Tesla, only to discover that it was supposed to be set at 45 PSI—20% higher than the ICE I had driven earlier. This surplus of air pressure provides an added layer of cushioning between the EV cabin and the road. Be prepared to pump air into your EV's tires more frequently than you might with an ICE. The effort is well worth it, as it significantly contributes to overall efficiency (which will, in turn, really help your range). Most manufacturers recommend monitoring EV tire pressure on a monthly basis or whenever there are substantial temperature fluctuations.

Road noise

EV enthusiasts adore the serene silence that electric vehicles offer. Unfortunately, the absence of engine noise can seemingly amplify the sound of tires rolling on the road, disrupting the tranquility of the ride. This phenomenon becomes particularly noticeable on surfaces like sturdy concrete or uneven roads. To counteract this, tire manufacturers minimize road noise by incorporating acoustic dampers or foam within EV tires. However, while these noise-reducing materials contribute to a quieter ride, they might also make the tires stiffer. Striving for silence could potentially impact the tire's traction capabilities by preventing the material from gripping the road as well.

Ian Coke, director of quality at Pirelli, talks about the options to design a quiet tire:

There's a variety of technologies out there. [Tread] pattern is one aspect. There has been a big uptake in noise-cancellation systems, which [involves] an open cell structured foam [being] placed inside the tire; the sponge absorbs the noise, and [the noise cancellation] stops it from being carried through.

What is special about EV tires?

Nowadays, there is a whole new set of specialty EV tires that are meant to optimize these special considerations for electric cars. They are built to handle the added weight and torque while muting road noise. However, the requirements for a good EV tire can be at odds with each other. You want low rolling resistance to maximize range, but need traction in order to enjoy the performance of your zero-RPM torque. You want to buffer the sound of the tires on the road, but also ensure longevity. It’s not a simple problem, and tire companies are racing to the finish line with proprietary optimizations. 

How does changing your tire affect your range?

Michelin product manager Steve Calder explains that

There can be about a 6 percent change in range between when the tire is new and when the tire's at the end of life.

And, depending on your specific needs, you may opt for a tire that prioritizes some features more than others.

For instance, Russell Shepherd elaborates on the effect of rolling resistance on range. In the EU, tires come labeled with a rolling resistance rating, and the difference between Michelin tires with the most and the least resistance can translate into a 15% difference in range. In general, a 20% increase in rolling resistance means a 5-8% loss of range. Another calculation puts the range difference between low rolling resistance and performance tires at around 50 per 200 miles - that’s 25%!

What about tire size?

The rule of thumb is that wider tires provide better traction and handling, since there is more contact between the wheel and the road. However, this can also cause range losses through aerodynamic drag and friction.

Related, is how wheel size affects range. As demonstrated with Tesla wheel sizes, range generally drops with larger wheels.

Here are some tips to keep your tires in good shape for as long as possible:

• Check alignment - this is a frequent issue, especially with Teslas. If your tires are wearing unevenly or faster than seems reasonable, it’s a good first step. 
• Check pressure - since EV tires are so heavy, they need all the PSIs the sticker says. Even a slight lack of tire pressure can affect rolling resistance, leading to range loss. However, be careful overfilling your tires to game range. This can lead to a lack of traction, especially on wet or icy roads. 
• Rotate tires - Tesla recommends every 6,250 miles
• Performance tires tend to be softer to “grip” the road more, but they will also wear down faster.