Tire Pressure and Fuel Mileage

How to Increase your Fuel Economy With Proper Tire Pressure

You may have heard politicians and celebrities speak about the importance of choosing the right tires and proper tire inflation for safety and fuel conservation. I heard the talk and wondered; how important are tires in the big picture of gas consumption? So I went on an informational search to get answers. I found the Transportation Research Board Special Report on Tires and Fuel Economy. Let me summarize what I found.

The study focused on passenger tires sold for replacement; however their findings also apply to original tires. They concentrated on energy that is consumed by rolling resistance.

I know that sounds technical, but stick with me. Most of the fuel for your car is consumed as heat, during engine combustion and friction on the way down to the wheels.  Rolling Resistance’ refers to the amount of force at the axle that is needed to make a loaded tire roll. If you can reduce the rolling resistance you will improve fuel economy. A 10 percent reduction in rolling resistance for most passenger vehicles can improve fuel economy by about 1 or 2 percent.

Tires are the main source of rolling resistance so the choice of design, construction and materials used in the tires as well as tire maintenance and operating conditions is key to tire longevity and gas efficiency.

The original tires on a new car usually have less rolling resistance then replacement tires, so finding a tire that closely resembles the original tire is usual your best bet. Manufacturers tailor tire properties to each of their vehicles and this helps cars meet federal standards for fuel economy. On the other hand, replacement tires are made for a broader market to fit many cars.

Rolling resistance is not static over the life of the tire. Tire maintenance makes a big difference. Maintaining the correct tire inflation is essential in reducing rolling resistance because low air causes the tire to reshape or deform more then normal. The average passenger car tire should be inflated between 24 to 36 pounds, (see manufacturer’s specifications). You often can’t see an 8 pound decrease in tire inflation just by looking, but it can result in a 1 to 2% increase in fuel consumption. Periodically checking your tire pressure will save you gas and extend the life of your tires. You can also increase your tires efficiency by keeping the aligned and balanced.

Modern tire innovations, like radial tires, have decreased passenger tire rolling resistance by as much as 30% over the last 3 decades. Thicker and deeper treads on tires usually result in higher rolling resistance but better durability. Manufacturers are now looking for ways to reduce rolling resistance without reducing the wear resistance in tires by changing the amount of materials used along with tread dimensions and design.

The report concluded that a national 10% reduction in rolling resistance could result in an annual fuel savings between $2 to $4 billion in the US. The report also stated that a 10% reduction is both feasible and attainable within 10 years.[1]

In conclusion, I’m going out to check my tire pressure, but I realized I haven’t checked my tires in a while (I usually get someone else to do it), so I brushed up on the steps. Here they are in case you need a little too.

 

How to check your tire pressure

  1. Check your pressure when the tire is cold – driven less then 2 miles.
  2. Look in your owner’s manual for the standard cold tire inflation pressure. (It’s often also posted on the inside of the driver’s door.)
  3. Remove the valve cap from the valve stem on the tire.
  4. Press the air pressure gauge into the valve stem and read the number.
  5. If the pressure matches the manufacturer’s specifications, you’re done. Replace the cap and drive away. If the number is lower, fill the tires with air, then replace the cap and drive away. (Don’t drive away until you check all the tires.)





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References

1 Transportation Research Board Special Report 286: Tires and Passenger Vehicle Fuel Economy, 2006. Retrieved on May 20, 2010. http://www.onlinepubs.trb.org/onlinepubs/sr/sr286.pdf

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