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Tires could be costing EV owners an extra charge a year, study suggests
Bengt Halvorson
BENGT HALVORSON OCTOBER 26, 202

Over the life of an electric vehicle, tires can have a profound effect on electric vehicle range and efficiency.
That’s been given more nuance with a new collaborative study, between Geely Research Institute, Shanglong Linglong Tire Co., and ExxonMobil—and reported earlier this month in SAE International.

Over the life of an electric vehicle, the researchers found, the variation in rolling resistance alone, due to fluctuations in tire pressure, could mean 4% more energy needed, the study highlights. No wonder tire suppliers continue to develop airless tire designs like the Michelin one GM is currently testing for its Chevrolet Bolt EV, and engineers have dabbled with designs that recover energy as they roll or harness heat generated in flexing.


Chevrolet Bolt EV fitted with prototype airless tires from Michelin
Chevrolet Bolt EV fitted with prototype airless tires from Michelin

The Chinese study assumes an average annual vehicle distance of 12,000 kilometers per year; but expanding this out to the typical U.S. vehicle distance of 12,000 miles per year, it amounts to nearly 58 kwh per car, annually.

For most of today’s full long-range EVs, like the Chevrolet Bolt EV or Nissan Leaf Plus—or the Tesla Model 3 Standard Range Plus—that’s about a full charge lost not to power electronics or battery technology, but something as simple as a tire swap.

The researchers do point out that the reduction in pressure loss and rolling resistance could allow automakers to use a lighter/cheaper battery.
Extending that estimate out for the entire Chinese market, given cumulative EV sales, simply changing the tire could save 90 gigawatt-hours per year—enough to power 50,000 Chinese households.

Environmental impact of tire pressure control - ExxonMobil
Environmental impact of tire pressure control - ExxonMobil

The team found air retention to be an issue, with 48% of the tires examined falling into what was judged to be a “poor” category for that—meaning that there will be significant air loss over time simply from normal use, leading to lower fuel economy or efficiency if pressures aren’t routinely topped off.

Tire-pressure alert systems aren’t the solution either. According to the study, while early tire-pressure monitoring systems were intended mainly to prevent the catastrophic—underinflation by 20%—the latest systems are programmed for a trigger of 2.5%. That might be fine for safety, but it still reflects an efficiency loss.
Although much attention has been paid to tread, compound, and what’s on the outside of the tires going into many EVs, the researchers point out that for maintaining pressure the solution might be addressing what’s inside the tire. With a new material for the inner liner, the tire was able to retain pressure 33% better, based on a calculated six-month period.

Checking tire pressure - AAA
Checking tire pressure - AAA

The study notes that based on ExxonMobil road testing, with greater attention to tire pressure loss—and rolling resistance—across the lifetimes of the tire and electric vehicle, EV range could be improved by an astounding 3% to 7%.

That largely confirms the conclusions from a number of smaller, more anecdotal tests—that the range difference from tires alone can often be underestimated.
The findings will help inform decisions about tire specifications for the next generation of EVs from the Geely Auto Group, which includes Geely, Volvo Cars, Polestar, and Lynk & Co.
 

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With every 10 degrees change in temperature tires lose between 2 and 3 pounds and vice versa as temperatures rise.

I have a good quality air compressor and I constantly check my tires both with a high quality gauge and the TPS on the dash.

FYI I also put 2 lbs more than the recommended psi: I find the ride fine, handling a bit better and fuel economy about 5% better. Also wear on the tires is better.
 

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This is the downside to EVs being so heavy. But at least tire manufacturers seem to be on it to make adjustments.
The MMe Michelins are Extra Load rated to compensate for the weight. I wonder how high the PSI is?

Some michelin Primacy A/S also have self-seal tech, where the lining will seal around nail and other punctures, and fill the hole when the nail is removed (not sidewall punctures)
 

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That's a good question. I'd be curious to see what the PSI is as well. I wonder if any of the models at the Mach-E Tour events has the sticker inside the door that says what the tire pressure is supposed to be set at.
 

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That's a good question. I'd be curious to see what the PSI is as well. I wonder if any of the models at the Mach-E Tour events has the sticker inside the door that says what the tire pressure is supposed to be set at.
Recommended PSI is 39. Tires are Michelin Primacy 225/55 R19 103H (on the Premium).
 

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I WHOLEHEARTEDLY AGREE WITH THIS ARTICLE! I was "talked" into buying cheaper tires for my CMAX Energi. I saw a 8-10 MPG drop in fuel economy for trying to save $100-200 on the cost of the tires. I drive 35k miles a year. That drop cost me more than I was trying to save. BUY THE RIGHT TIRES THE FIRST TIME or it will cost you!
 
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