Report: In Small Cars And EVs, Smaller Tires Could Save Fuel

June 8, 2011
U.S.-spec 2012 Fiat 500c

U.S.-spec 2012 Fiat 500c

2011 Scion iQ

2011 Scion iQ

With signs that minicars might finally be taking off in the U.S.—signaled by the arrival of models like the Fiat 500, Ford Fiesta, Scion iQ, and a host of potential ones—it could be time to give smaller wheels a new chance.

Why? Because, Motor Trend reports, a new generation of higher-quality ten-inch tires are here. Michelin has produced a new 175/70R10 tire, specifically for city cars, that weighs about three pounds less than a 175/65R14 tire.

Twelve pounds and some rolling resistance might not sound so significant, but it is. According to Michelin, MT reports, the new smaller tires might be especially of use on new urban electric vehicles, where the use of tires designed for larger vehicles with internal combustion engines could account for 30 to 40 percent of overall energy consumption. Reducing that means greater range—which is especially important right now, on the cusp of EV adoption.

Tires, even on the smallest, entry-market vehicles, have become larger in recent years. In the 1980s, the mainstream tire size was the 14-incher; then in the 1990s, 15- and 16-inch sizes became increasingly common on affordable vehicles. Sidewalls continued to get even shorter and this past decade gave way to low-profile, large-diameter chromed insanity in the way of 20-inch wheels and beyond.

Designers have for well over a decade now penned vehicles with increasingly large wheels and wheel wells, so eventually, smaller, less exaggerated wheels might come back in style. It could certainly bring some packaging advantages, as huge wheels require large wheel wells that eat up trunk or cabin space.

The downside of these big rollers—aside from their sometimes harsh ride quality—is that they add weight and raw materials, and sometimes actually increase rolling resistance. And that definitely factors into gas mileage.

At the same time, on bigger, heavier vehicles it might not pay to downsize if you don't change the compound, as smaller-diameter wheels and tires typically do have more rolling resistance. One Michelin design, a 205/55R19 wheel, is measurably more efficient than existing 205/55R16 designs.

What's the message to take away? Don't take the impractical 22s you might be rolling on as the look of the future, and be prepared to see some smaller (or skinnier) wheels on next-generation fuel-savers.

[Motor Trend]

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