Math proves big tire sidewalls are better for the planet

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Ferrari 488 Pista fitted with carbon fiber wheels

Many car owners prefer low-profile tires and big wheels for their look, but this Engineering Explained video shows that this can be an extreme case of style over substance. Host Jason Fenske declares that, in a way, big tire sidewalls could help save the planet.

The video focuses specifically on how wheel-and-tire choice can affect electric-car range. As detailed in a previous video, electric cars are more sensitive to changes like these than internal-combustion cars because they carry less energy onboard. So even a small drop in efficiency can have a big impact on range.

To calculate the effect of wheel diameter on range, Fenske used coast-down data from Tesla, which the automaker submits to the EPA for efficiency testing. All automakers are required to submit this data, which is used to help calculate efficiency ratings, but Tesla submits different figures for each of the wheel diameters offered on its cars, making a direct comparison possible.

Fenske calculated the range of a Tesla Model 3 Performance driven at a consistent 75 mph was 40 miles less with 20-inch wheels than with 18-inch wheels. Similar results were observed for the Model S Performance and Model X Performance, albeit with smaller differences between the different wheel options.

Ferrari 488 Pista fitted with carbon fiber wheels

Those differences add up to more electricity used by cars with bigger wheels. So if you really want to reduce emissions, get tires with bigger sidewalls. Those tires will likely be cheaper than low-profile rubber, and will save you money on electricity, Fenske noted.

The video also details how tire width and tire compound can impact electric-car range. Wider tires have a larger contact patch, increasing grip, but they also increase the car’s frontal area, creating more aerodynamic drag. However, switching from a 205 millimeter to a 305 millimeter tire only decreased range by the equivalent of 1.7 miles over 200 miles of driving.

Electric cars also typically use low-rolling resistance tires, which emphasize efficiency over grip. Stickier tires might make your electric car handle better, but they will likely come with a range penalty. Fenske calculated that a performance tire decreases range by the equivalent of 53 miles over 200 miles of driving.

Watch the full video to see all of the math behind these conclusions, and find out if you agree with them.

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