Tires canplay an important role in making cars more fuel efficient.Many motorists are familiar with the concept of maintaining propertire pressure to attain optimal gas mileage. Tires that areoverinflated or underinflated will not be able to maintain properrolling resistance, which will reduce the vehicle’s gasmileage. In addition to tire pressure, many motorists wonderwhether tire size is also a factor.
The impact tire size can have on performance, including fuelefficiency, was examined in a recent issue of Car and Driver magazine.The article, titled Plus-Size Models: Testing the performanceeffects of upsizing wheels and tires, was written by TonyQuiroga and appeared in the April 2010 edition. The findingsin the article were based on tests involving “nearly identicalGoodyear Eagle GT ultra-high-performance all-season tires in allfive sizes, inflated to manufacturer-recommended pressures.”In addition, they “used the stock steel wheels for the 15-inch testand went to the aftermarket for the larger wheels, as most ownerswould do. The aftermarket wheel … was a cast-aluminum ASA GT1,which is available in 16- to 19-inch sizes on the Golf.” Onesentence offers a succinct summary: “What’s immediately apparentfrom the results is that as the wheel-and-tire packages get largerand heavier, acceleration and fuel economy suffer.”Specifically, the author cited a “10-percent drop in fuel economy …from the 15s to the 19s.”
The question of whether tire size affects gas mileage is not anew one and it is not limited to cars or personal vehicles.It was examined in an article in the December 2000 issue ofLand Line Magazine, which is described as a businessmagazine for professional truck drivers. The article examinedthe issue of how tire specifications can affect fuel economy.Paul Abelson, the magazine’s technical editor, interviewed PeggyFisher and Asa Sharp, both considered experts in this field.They addressed the issue of how “tire size and profile affect fueleconomy.” They explained, “When low profile tires first cameout, they were about 4 percent more fuel efficient. Low profilesidewalls are shorter, and therefore stiffer. That reduces flex butonly slightly. Smaller tires weigh less than larger tires, so lessenergy is needed to get them rolling, and also to stop them.”
The experts, however, offereda word of caution lest truck drivers assume they should switchto smaller tires:
It is probably not worth switching to smaller tires,since any gains in fuel economy would be offset by the added costof re-gearing to keep your engine operating in its most efficientrpm range. Remember, power and economy are affected bytransmission, drive axle ratios and tire size (revolution permile). Change one, and you throw the equation off. With today’s newtires, there is virtually no difference in mpg due to tiresize.
As with many questions related to cars and tires, the answer tothis question can have nuances, conditions, and variations.The answer that applies to truck drivers is different from theanswer for the typical motorist. Before purchasing new tires,consider whether some of the aforementioned factors, such as yourvehicle’s transmission, would be impacted positively or negativelyby new tires, particularly if they are of a very differentsize. Tire treads can also affect your fuel efficiency, butdepending on the conditions you drive in, safety should be apriority. There are many factors to consider when buying tires… let the experts at DunnTire help answer your questions.
