There are a lot of things that come together to make your car fuel efficient. Auto companies spent millions of dollar on the research and development of a new engine or body design to make them as efficient as possible and as aerodynamic as possible. The new Toyota Prius is a prime example of this. The new hybrid is 10% more fuel economical than the previous model.
Vehicle components like engine and transmission affect the efficiency more than anything else. But there are other smaller things that come together and make the car affordable. And energy-saving tires are one of those necessary parts. Not many might know, but tires play a significant role in maintaining fuel average of your car. And often this side of the story gets neglected when choosing tires for your vehicle. According to the United States Environmental Protection Agency, tires affect the fuel consumption of a vehicle by as much as 17%.
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And what affects the most when it comes to tires and fuel economy is the rolling resistance of that tire. Higher the rolling resistance, more power it is required from the engine to rotate that wheel. And of course, when the rolling resistance is less, it’s easier for the engine to spin the tires. Hence, fewer revs and less required fuel. The rising cost of fuel in last three or so decade internationally forced the automakers to come up with ways to make their cars more fuel efficient. The tire makers also came up with tires that would grip nearly as good as regular tires but with less rolling resistance.
Tire manufacturers reduce the rolling resistance through a couple of methods, one of them is by reducing the internal friction. Internal friction is caused by contact of the road and footprint of the rubber. Other things the count are the compound of the rubber used in the tire and the tread pattern as well.
Also Read: Decrypting The Tyre Sidewall
These are of course tires for your general use and are not recommended for high-speed driving or racing. Read the side marking of the tire for the exact safe speed limit. The automakers around the world are moving towards these fuel efficient tires. All new hybrids are being sold with such tires. These tires are also considered relatively more environmentally friendly.
If you have any experience with such tires, please do share with the rest of the readers in the comment section below.
Watch the video for the better understanding of rolling resistance.
I have Michellin Energy Xm2 in two of my cars running on 5W30 fully synthetic oils(which are claimed to be fuel efficient as well). I havent been able to detect any difference in mileage so far, maybe its a negligible difference or just nothing at all. Drive under 2k Rpms at 60km/h with a very light foot with any tyre or oil and then see what fuel eficiecency is.
Michelin Energy Saver is the tyre for least fuel consumption. Energy XM1 and XM2 have no special features for reducing consumption.
Energy Saver has extremely soft sidewalls, This means longer stopping distance, and tyre tends to lie down on the sidewall (does not maintain its shape) during even the normal, slow-speed cornering that is possible in the urban traffic. In addition, when the tyre is in this position, the sidewall gets rubbed on the road (you can see the marks after a few months of use), possibly picks up nails or thorns and the tyre is gone. Because (for any tyre) the sidewall is much softer and/or thinner than the tread, it is much easier to be penetrated by any nails, thorns or shards of glass. And for Michelin Energy Saver, this effect is pronounced because of extra soft sidewall.
Michelin Energy Saver used to cost much less than Energy XM1 and XM2, though belonging to the same series. A good alternative is Dunlop Lemans LM702. It is much lighter in weight compared to other brands of the same size and has much less road noise compared to Opus Windsor (now obsolete), EC-201, LM-701 etc., has a beautiful pattern, readily available and durable, and the sidewall is hard enough for decent cornering yet soft enough to provide a comfortable ride.
Internal friction:
I think it is not clear to the writer about internal friction. Internal friction happens between the elements of the tyre itself. As the tyre is under load, the parts such as steel belts, nylon belts, and even the solid rubber twists and distorts (in fact it is a technical term in mechanics called internal shear). This internal shear requires energy to happen. As per the law of conservation of energy, this energy will not be created on the sopt out of thin air, but this energy will have to come from somewhere. This energy (internal friction losses) is derived from the machine rotating the wheel. Which is the engine.
Therefore to make a better design, if we reduce internal friction, we also reduce the chances of a certain quantity of energy which is going to waste because it would not provide useful output, but will provide useless output in the form of heat released to the surroundings due to the internal friction.
The greatest breakthrough for internal friction was the introduction of radial tyres. They have much less internal friction because the skeleton’s belts do not cross each other, therefore there is no “knife action” during the time the tyre is deforming under the load. Now the load on the tyre can be many types such as weight of the car, steering (the effect of turning) load, acceleration, braking, etc.
Now begs the question: How does reducing internal friction reduce rolling resistance? This could be explained by an example.
Suppose tyre A needs X energy to move. 10% of this energy is consumes by the parts of those tyres moving against each other (or rather, trying to move against each other) as the tyre is loaded in various manners. (An example of this deformation is hold a book and then try to make a roll out of it. The edges of the pages are all in a precise line initially, but after you roll the book, they sort of “fan out”. Many students write their name on the book by doing this.When this “fanning out” is happening, each page is moving against the other two pages it is sandwiched between. And where there is movement, there is friction too. Similar thing happens in tyre too. Now if the book has some butter paper, internal friction against being rolled up would be less, if the paper is coarse, internal friction of the book would be greater too.)
Now if the internal friction of the tyre is reduced, the energy lost in overcoming the internal friction would be reduced, thus resulting in less fuel consumption. Less fuel consumption would decrease the environmental impact of fossil fuels, therefore it is highly environmental. If the reduction of internal friction requires some hazardous chemicals or increases the occupational safety hazards of the workers of the manufacturer, or the repair shops, or the users, the level of environmental-ness could be debatable.
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Low rolling resistance tyres offer a longer stopping distance.
Arif please suggest good tires manufacturers and dealers in Pakistan. For local cars. Especially in Rawalpindi-Islamabad.