Let it roll: Low-resistance tires save drivers money

Jan 17, 2014
Let it roll: Low-resistance tires save drivers money

(Phys.org) —Drivers who switch to tires with low rolling resistance can save an average of nearly $150 a year, says a University of Michigan researcher.

"One parameter on which differ is their rolling resistance—the force resisting the motion when an object rolls," said Michael Sivak, research professor at the U-M Transportation Research Institute. "Tires with low rolling resistance roll easier and, therefore, get better mileage than tires with high rolling resistance."

The U.S. Transportation Research Board estimates that a 10 percent increase in tire rolling resistance will result in about a 1.5 percent decrease in vehicle fuel economy.

Sivak examined the rolling-resistance measurements for 63 new same-sized tire models obtained by Consumer Reports at the same load and inflation pressure to calculate the fuel consumed annually by an average driver. He then calculated differences in fuel used (and money spent) between tires at the extremes of rolling resistance.

The tires represented a cross-section of the currently available T-, H- and V-speed-rated tires for light-duty vehicles on the U.S. market (maximum speeds for each of these types of speed-rated tires are 118 mph, 130 mph and 149 mph, respectively).

Rolling resistance (RRf) for the combined set of all tires examined ranged from 6.89 lbs. to 12.5 lbs., with a median of 10.28 lbs. For the average vehicle currently on the road, the rolling resistance extremes translate into a maximum fuel economy of 22.4 mpg (RRf at 6.89 lbs.) and a minimum of 20.7 mpg (RRf of 12.5 lbs.), with a median of 21.4 mpg (RRf at 10.28 lbs.).

"Consequently, the obtained rolling resistance extremes yield a minimum and maximum annual fuel consumption of 505 gallons and 547 gallons, respectively," Sivak said. "At the average 2013 price of regular gasoline, the obtained fuel-consumption results in a $147 difference in the annual cost of gasoline per light-duty vehicle."

For the combined set of all tires, the added fuel consumed with tires at the current maximum rolling resistance represents an 8.3 percent increase compared to the fuel consumed with tires at the current minimum rolling resistance.

Sivak's study is the first comprehensive evaluation of how much fuel a driver can save when using tires with low rolling resistance.

Explore further: Fuel economy of vehicles sold last year at record-high

add to favorites email to friend print save as pdf

Related Stories

Fuel economy of vehicles sold last year at record-high

Jan 10, 2014

Gas mileage of new vehicles sold in the U.S. was 24.8 mpg in December, the same as the average for all of 2013—the best annual mark ever, say researchers at the University of Michigan Transportation Research Institute.

Vehicle fuel economy up in October

Nov 13, 2013

Gas mileage of new vehicles sold in the U.S. rose 0.2 mpg last month, say researchers at the University of Michigan Transportation Research Institute.

Fuel economy up 23 percent since 2007

Dec 06, 2013

Gas mileage of new vehicles sold in the U.S. was 24.8 mpg in November, up 0.1 mpg from the revised October figure, say researchers at the University of Michigan Transportation Research Institute.

Recommended for you

Are electric cars greener? Depends on where you live

Nov 25, 2014

Long thought a thing of the future, electric cars are becoming mainstream. Sales in the United States of plug-in, electric vehicles nearly doubled last year. Credible forecasts see the number rising within ...

User comments : 11

Adjust slider to filter visible comments by rank

Display comments: newest first

OZGuy
1 / 5 (1) Jan 17, 2014
Given I'm concerned with stopping safely and rapidly in the event of an emergency, does anyone know what impact this would have on braking?
wealthychef
not rated yet Jan 18, 2014
Is rolling resistance commonly reported for tires? As a consumer can I factor this in?
alfie_null
1 / 5 (1) Jan 18, 2014
Given I'm concerned with stopping safely and rapidly in the event of an emergency, does anyone know what impact this would have on braking?

The author's merely taking data from a magazine article and applying some simple math. Talk about inexpensive research. He expresses the result solely in terms of fuel costs saved, ignoring a bunch of factors that otherwise have to go into selecting an optimal tire. Factors like your traction. How about adverse weather performance? Durability (how many miles do you get)? Ride comfort and road noise? The cost of the tire itself?
PeterPiker
not rated yet Jan 19, 2014
Such tires may also reduce road noise since it takes energy to produce sound.
TheGhostofOtto1923
3 / 5 (1) Jan 19, 2014
U of Mich researchers should know that these tires aren't very good in the snow.
Eikka
not rated yet Jan 19, 2014
Low rolling resistance tires are made of harder rubber to minimize energy loss due to deformation, and they're built narrower to minimize contact with the road surface, and larger in diameter to stretch out the contact area to smooth out the bumps to stop energy loss to vibrations. Think bicycles versus wheelbarrows.

Unfortunately this means the wheels have worse dynamic traction (slip) characteristics, both due to the reduced contact area and harder rubber, because there's less adhesion to the road surface so that when you lose grip, you lose it suddenly and sharply. That applies in acceleration, braking, and cornering. Once you start a wheelspin, it just spins.

That's why racecars have fat soft tires even though it loses them lots of power. Old time racers had narrow motorcycle wheels for speed, because they didn't have as much power, but they in turn were terrible around corners and incredibly dangerous to drive.
Eikka
not rated yet Jan 19, 2014
U of Mich researchers should know that these tires aren't very good in the snow.


On the contrary. Narrower tires are better in snow because they exert more surface pressure, so they bite into it instead or riding on top of it. The most dangerous thing in the winter is if you ride on top of a shallow snow crust on top of ice

Studded winter tires are always narrower than summer tires to get more pressure on the studs.

It's all a bit of a balancing act. Wet weather tires would also be better if narrower, because you're trying to avoid hydroplaning, but again on dry weather the higher surface pressure would wear them out quicker, and also wear the road surface out quicker.
TheGhostofOtto1923
1 / 5 (1) Jan 19, 2014
On the contrary. Narrower tires are better in snow because they exert more surface pressure, so they bite into it instead or riding on top of it. The most dangerous thing in the winter is if you ride on top of a shallow snow crust on top of ice
If you look at a typical snow tire you'll see they have deep patterns and gaps.

"Winter Tires-Winter tires are notorious for losing mpg as their tread patterns often create more resistance to the road that summer and all-season tires. "

"Snow tires (also known as winter tires) have tread patterns specifically designed to dig down and bite into snow and ice, plus they are made from softer rubber compounds that retain their flexibility in cold weather, allowing the tire to better conform to the surface of the road"

-Or you could make up your own bullshit explanation.
nik_kelly_54
not rated yet Jan 19, 2014
How do 'low resistance' tyres handle pot-holes and parking up kerbs ??

I've seen several drivers come to grief, especially those with low-profiles and alloy wheels...
Eikka
not rated yet Jan 20, 2014
If you look at a typical snow tire you'll see they have deep patterns and gaps.


Yes, again to increase surface pressure by reducing contact area, and also give the snow somewhere to go under the tire, and to give it mechanical grip with the ground. Winter tires are not low rolling resistance tires, but they have some of the features, i.e. the narrower profile.

You have to understand that when a tire is rolling, its surface is essentially stationary against the ground, so static friction applies. In that situation, the size of the contact patch doesn't matter because the resulting friction force is the normal pressure (weight) per area times contact area times coefficient of friction. The size of the wheel essentially cancels out of the equation, so the narrower wheel has exactly the same grip as the wider wheel - as long as it doesn't start to slip.

TheGhostofOtto1923
1 / 5 (1) Jan 20, 2014
The size of the wheel essentially cancels out of the equation, so the narrower wheel has exactly the same grip as the wider wheel - as long as it doesn't start to slip.
Again, your imagination does not reflect actual tire design. Low resistance tires are not as good as regular snow tires for winter conditions because they're not engineered that way.

Snow tires are soft rubber with aggressive tread patterns because engineers have found that that's what works best in cold and snow. These features decrease mpg.
You have to understand that
You have to understand that tires are the result of engineering and field testing in actual conditions, not speculating and imagining.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.