Tires may seem to be an unlikely eco-product. But, according to a new market report from Smithers Rapra, the global market for "green tires" will reach $70.6 billion by 2017 or 28% of the total tire market.

Can We Save Energy with Vehicle Tires?

Len Calderone for | AltEnergyMag

 

One of the things that we would not expect to be energy efficient is vehicle tires. Yet, fuel efficiency and tires actually go hand-in-hand. The demand for increased fuel efficiency in vehicles has been met not only by auto manufacturers, but also the tire manufacturers. Because of advancements in tire performance, drivers can get more mileage out of every tank of gas and shrink their fuel budget.

It's smart to keep that in mind, especially since we have no idea where gas prices will be in the future. In terms of fuel efficiency and tires, each tire is manufactured and tested to roll in a very specific way across a road surface. In order for that tire to roll, exactly as intended to achieve maximum efficiency and optimal tire performance, it's necessary for tires to be properly inflated. Variables such as over-inflation or under-inflation cause tires to be less fuel efficient.

Rolling resistance measures how much effort the car has to put into making the tires roll along the pavement. Tire manufacturers have responded to environmental concerns and high gas prices by investing in more fuel efficient tire technology, known as low rolling resistance tires. These tires are designed to offer low resistance to the vehicle's motion as the tires roll. This low resistance requires less energy from the vehicle's engine, using less gas.

When a tire rolls across the road, creating resistance, many variables come into play. Other types of resistance also occur regardless of the size of the tire's footprint. These are based on various tread designs and their interactions with the road surface. The science behind low rolling resistance tires is quite exciting. Approximately 5–15% of the fuel consumed by a typical car is used to overcome roll resistance.

As the wheels turn to move the vehicle forward, the tires change their shape in order to make and maintain contact with the road. The section where the tire meets the road is called the contact patch. All of the forces needed for acceleration, braking and cornering are transmitted through this contact patch. As the tire makes contact with the road, heat is generated, and energy is consumed and is called rolling resistance. Tires having a low rolling resistance require less energy to deform into the contact patch, reducing energy loss.

The challenge here is to have the tire flex just enough to meet the road while minimizing internal friction and wear. Tire makers have been experimenting with compounds, such as styrene-polybutadiene rubber and neodymium-polybutadiene rubber, along with silica to reduce the rolling resistance. Construction and materials are important, but tire pressure, vehicle weight and speed all play a role.

Low rolling resistance tires are said to enhance fuel economy over the life of the tire, resulting in less money being spent at the pump. Goodyear claims that their Assurance Fuel Max tire reduces rolling resistance by up to 27%, improving fuel economy by 4%.   Michelin states that their Energy Saver A/S tire can save up to $400 in gas over the life of four tires. As more auto manufacturers continue to meet higher fuel economy standards, it is likely that a new vehicle will come with low rolling resistance tires as standard.

The problem with low rolling resistance tires is that there is no federal standard to make the claim. Therefore, if a tire manufacturer claims that its tires will increase fuel economy by 4%, they are comparing that figure to their own tires. The goal of low rolling resistance tires is to help vehicles meet the Corporate Average Fuel Economy (CAFE) regulations. If that is accomplished by the vehicle itself, low rolling resistance tires would not be needed. There needs to be a federal benchmark for these tires and not just the manufacturer's comparison.

Rolling resistance has traditionally been measured through an official Society of Automotive Engineers (SAE) test procedure known as J1269. It measures the force required to roll a tire against a dynamometer at a fixed speed of 50 miles per hour. A rolling resistance differential of 20 to 30% is not uncommon among tires of similar size, type, and performance. Tire choice can have a larger impact on fuel economy than most people realize with an efficiency difference of up to 60%.

Low rolling resistance tires require a greater stopping distance. Rolling resistance is defined as the force resisting the motion when a tire rolls on a surface. Low rolling resistance tires are designed to have less resistance. Therefore, the tradeoff is better fuel economy versus a lower traction rating. Braking distance is greater with low rolling resistance tires as distances increase as the rubber grips less. Is this trade-off justified? Maybe, if the reason is to decrease the traction with the road and increase mileage.  

Tires may seem to be an unlikely eco-product. But, according to a new market report from Smithers Rapra, the global market for "green tires" will reach $70.6 billion by 2017 or 28% of the total tire market. Up until now, the growth in green tire production has resulted from governmental pressures, raw material shortages and price volatility, with consumer demand playing a very minor role. This is largely due to a lack of awareness of the green tire technologies, such as the low rolling resistance tire technology, but in time green tires should be standard fare.

To get the most out of your tires be sure to keep your tires properly inflated. Check the label on the driver's doorjamb for the correct pressure. The pressure should be checked at least once a month when the tires are cool. If the tires’ air pressure is too low, the tires won’t perform as they are designed.

There isn't any magic that can dramatically increase mileage overnight. Other ways to improve mileage is to drive slower, as the slower you go, the better fuel economy you have, so try to stick to the speed limit and your fuel economy will improve. Accelerating rapidly will use up more gas than if you were to slowly accelerate up to speed, and use the cruise control to help maintain a constant speed. Using the correct weight of oil in your car will cut down on engine friction, and this could account for at least as much in fuel-efficiency gains as the tires.

If you are satisfied with the tires that came with the car when it was new, consider replacing them with an identical set. Low rolling resistance is a common trait of original-equipment tires.

 

For additional information:

  1. https://www.wbdg.org/ccb/GREEN/REPORTS/cgrtirerollingresistance.pdf
  2. http://www.epa.gov/smartway/forpartners/documents/verified/420f12024.pdf
  3. https://www.tirerack.com/tires/tests/testDisplay.jsp?ttid=121

 

Len Calderone - Contributing Editor

Len contributes to this publication on a regular basis. Past articles can be found in the Article Library and his profile on our Associates Page

He also writes short stores that always have a surprise ending. These can be found at http://www.smashwords.com/profile/view/Megalen

Len Calderone

 


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