22.11.2015

Many drivers strive to fit the widest tires with large rims to improve the visual appearance of the car. However, few people think about the direct impact of tires on fuel consumption during operation. The main subject of disagreement is the tire rim and profile width. Today, all drivers are divided into two directly opposite camps. One part of drivers is trying unsuccessfully to prove to others that by purchasing smaller tires they have been able to significantly increase the fuel efficiency of their car.

Arguments of the defenders of the theory

Advocates of the theory offer arguments that much more force is needed to spin larger wheels. Accordingly, for the processes of starting movement and acceleration, an increased amount of gasoline will be required, however, the average speed will increase by 10-15 km / h (which will play into the hands of fans of an active driving style). Despite the objectivity of the data, it is extremely difficult to calculate the exact percentage of increased fuel losses, since it depends on a number of very diverse factors (disk weight, technical condition of the machine, etc.).

The most ardent defenders of the theory are sure that fuel consumption increases non-linearly, therefore it directly depends on the selected speed mode. In the process of driving at low speeds, the increased fuel consumption will not be significant, but with the development of speeds above 40-50 km / h, its consumption will increase sharply.

Opponents' arguments

In an attempt to find out the truth about the effect of wheel size on fuel consumption, most experts resort to knowledge of physics. Due to this, there is a theory that low fuel losses will cause an increased number of engine revolutions, because the work will be performed equally. Gasoline consumption will mainly depend directly on the mass of the vehicle and aerodynamic braking.

The existing "theory of the car" implies the presence of a special formula, which can be used to calculate the directional consumption of gasoline Qs, which makes it possible to neglect the dynamic values \u200b\u200bof the radius. In this case, the used tire profile height must be taken into account: the higher the profile height, the greater the fuel consumption.

Profile width and its role in fuel efficiency

Probably everyone understands that wheels with a wider profile require more fuel, because the weight of such a wheel will be large. In addition to this, the engine will require increased effort to move the machine. In addition to weight, the contact patch area usually increases, and with it rolling resistance and acoustic noise.

The fact that the car consumes much more fuel than stated by the manufacturer: the standard driving cycles until recently differed greatly in terms of load from real operation. But sometimes the fault lies with the driver.

Wider tires of larger bore on heavier rims lead to a noticeable drop in dynamics and an increase in fuel consumption. Well, I don't need to explain how pressure and fuel consumption are related. It is not for nothing that in recent years TPMS pressure monitoring systems have become standard equipment on all machine classes. And in the US and Europe from 2014, all new passenger cars must be equipped with a similar system.

I will not open America: the higher the pressure in the wheel, the lower the fuel consumption. True, it does not decrease linearly; after a certain threshold, fuel consumption remains almost unchanged. On the other hand, the negative phenomena associated with pumping are becoming more and more noticeable. And this is not only a loss of comfort, but also a deterioration in the grip of the tire, and a general deterioration in handling due to a violation of the frequency characteristics of the tire-suspension ligament.

For this reason, tires have a recommended pressure, which the manufacturer always indicates in the documentation. Typically, for base tires, the data can be found on the information decals on the body. The optimal pressure indicated on the decals is determined by experiment and depends on the characteristics of a particular tire model. Exceeding it without understanding the processes occurring with the tire is not worth it.

An increase in the contact area of \u200b\u200bthe tire with the road surface is usually associated with an increase in the width of the tire. But an increase in the outer diameter is also a fairly effective measure. And this is understandable: the larger the outer diameter, the larger the contact patch. Unfortunately, the large wheel also has disadvantages, first of all - the increased masses of the tire and rim.

Downloading further!

In practice, fuel efficiency and grip do not mix well in one tire model. To achieve the lowest fuel consumption, a separate line of ContiEcoContact rubber is produced. It is distinguished by lower rolling resistance, lower weight, and lower resource. And, of course, maximum efficiency, even when compared to the ContiPremiumContact 6.

But in the line of tires of quite classic dimensions and appearance, there is also one completely new model. Don't be surprised, its dimension is 195/55 R20. I did not describe, the landing diameter is exactly 20 inches, and the tire width is 195 mm.

Remember what I wrote above about the relationship between the working pressure of a tire, its width and diameter, fuel consumption and grip? It looks like engineers have found a new way to reduce fuel consumption. This path is not easy, it includes several solutions at once.

First, the new tire material makes the wheel grip more efficient.

Second, the large outer diameter of the wheel improves traction even more. But the width of the tire has been reduced to reduce rolling resistance.

And most importantly, don't forget about pressure! The developed tread material allows you to maintain grip at a higher internal tire pressure, which, as you already understood, gives a benefit in economy.

Greetings, dear motorists and amateurs!
It is generally accepted by all of us that when installing wheels of a larger diameter on our car, we have to throw out a few extra hundred into the exhaust pipe, as the pet starts to eat more.
Every day the thought that this is not leaves me, I know that a lot has been said and retold about this, but now I will try to give my hypothesis on this matter, I think it will seem to you nonsense of an inexperienced boy who does not understand anything, but I don’t have much I understand and do not know in the car and I ask you the nut and key masters not to condemn if something is wrong, but to fix it.
Take a wheel that rolls 1m along the road in one revolution, we find not tricky calculations that for 100 km it will rotate 100,000 times.
Take a wheel of a smaller diameter, which in one revolution rolls 90 cm along the road, by the same calculation we find that for 100 km it will turn 111.111 times (the data is slightly rounded) It turns out that at the same distance, wheels of a larger diameter rotate at a lower frequency, respectively, the shafts, transmission gears and internal combustion engines too.
(Further material from an article from one of the sites) "The speedometer is driven from the transmission by a" flexible shaft "- a special cable that transmits rotation well. Since the same speedometers are found on different cars, a simple gearbox is used in their drive, the gear ratio of which is matched to the car. On a rear-wheel drive, the speedometer usually monitors the rotation of the secondary shaft of the gearbox. This means that the readings depend on the size of the tires, the gear ratio of the rear axle gearbox and the intrinsic error of the device. However, the gears of the reducer are not rubber - therefore, there is no perfect match of the speedometer to the tire size, and they still wear out ... The total error of readings up to 10% and even more is a common thing. Often this explains the records of yard racers.
Front-wheel drive transverse engine speedometers usually "service" the left wheel drive after the main pair. This means that the effect of rounding the road is added to the error of the speedometer and the influence of the tire size: when cornering to the left, the "indicated speed" is slightly less than in the middle of the car, and to the right - a little more. What is the impact of oversized tires? Replacing a 175 / 70R13 tire with a 165 / 70R13 tire or vice versa changes the speedometer reading by 2.5% "
It is clear from the article that when the tire is worn out (that is, when the diameter decreases) and when the wheel moves when turning to the right when the left wheel goes along the outer radius, the speedometer winds up excess.
How do we measure consumption? (your car has 14 wheels) We reset the odometer, drive for example 100 km and look at the fuel gauge, let's say it turned out 10 liters, you are happy!
You changed the shoes of your beauty on 16 discs, reset the odometer and drove off, having driven a hundred, you were horrified, your pet swallowed 13 liters. There is no limit to your disappointment!
In my opinion, this is an illusion caused by incorrect readings of the speedometer due to the fact that with a smaller wheel diameter the speedometer twists the real mileage and for the odometer to show 100 km, you will actually need to drive a shorter distance, and with a larger diameter you need to drive in reality a distance exceeding 100 km from here and increased consumption comes out.
If anyone has a desire to check, drive the distance from home to work on the same wheels, change the car and drive along the same path on these wheels (exactly along the same path) and compare the odometer readings, in my opinion the readings will be different.
Once again, I ask if something is wrong, if I'm wrong, correct it, but do not criticize, I am not yet experienced.
Thanks to all!
"We all know from childhood that this and that is impossible, but there is always an ignorant who does not believe in it. He makes discoveries." Einstein

Although it is often impossible to significantly reduce the average fuel consumption of a car, it is quite possible to save on fuel consumption by using high-quality energy-efficient tires. What tires are we talking about? What is behind this concept?

What are Energy Saving Tires

Let's dwell on the concept of energy efficient tires. By this is meant tires that have a sufficiently low rolling resistance. This creates little resistance or minimal friction in relation to the rest of the tires. Energy saving in tires occurs due to a decrease in the heating of the rubber in contact with the road surface and the rim of the wheel disk.

Rolling Resistance: Michelin Enegy Saver Example

Rolling resistance and grip

There is a rather big difference between the two. Although at first glance these concepts are closely related, they are not interdependent. This means that even if the rolling resistance decreases, the overall grip performance will remain the same.

Manufacturers of durable and reliable tires strongly advise to refrain from saving on such tires, because we are talking about safe driving and even someone's life.

Rolling resistance and pressure

In order to be guided by this indicator when buying tires, it is worth learning one unshakable rule - stiff tires have less rolling resistance. Therefore, it is very important to carefully monitor that the tire pressure is always at the optimum. Regardless of the rubber used, it is important that the pressure is always correct so that you can count on fuel economy.

If this parameter is always observed at the proper level, then the fuel economy can be from 0.3 to 0.5 liters for every 100 kilometers. Too low tire pressure increases the rolling resistance by changing the shape of the rubber itself. And if the car gets into extreme conditions on the road, this further affects the complications associated with handling. If the pressure is optimal, then this is a guarantee that the rubber will run easily on the roadway, thereby reducing the amount of harmful emissions from the car as a whole.

If there is free rolling, then it is quite normal to talk about the car's fuel economy. In order for fuel consumption to be uniform and economical, it is important to develop the most optimal driving style and manner. By avoiding aggressive driving, as well as sudden jerking of the car or emergency braking, you will be able to use fuel in the minimum amount and evenly.

How rolling resistance is measured

Although this is not specifically specified anywhere, if the rolling resistance of the tire is reduced by 10%, then the fuel economy increases to 2%, but everything will depend on both the car model and the quality of the tires.

Since 2012, the European government has mandated tire manufacturers to label new tires with fuel efficiency markings that are directly related to rolling resistance. A whole staff of professional engineers test different product models and compare them with each other. In the experiment, the amount of forces that are needed for rolling on 1 dynamometer is determined, taking into account that the speed of the car will be ~ 80 km / h. The tire is then graded from A to G, with the top letter representing maximum efficiency.

It directly affects the economy of consumption. Two parameters are at issue: wheel diameter and profile width. Soon, adherents of this theory appeared, who argued that they bought wheels of a smaller diameter or smaller width and already significantly saved on gasoline, and opponents who ridiculed this assumption.

Defenders' arguments

It is believed that with an increase in the diameter of the wheels, the engine requires an order of magnitude more effort to start moving. Starting and accelerating will require more fuel, but the top speed will increase by 5-10 km / h. At the same time, it is extremely difficult to name the exact fuel losses, since gasoline consumption depends on various factors, including weight.

The adherents of this version believe that the flow rate increases non-linearly and depends on the speed of movement. At low speeds, the difference in consumption will be negligible, and at high speeds or during acceleration, fuel consumption will increase significantly.

Opponents' arguments

In an effort to find out how the size of tires affects fuel consumption, many turn to the laws of physics, examples from life. Many of them argue that a slight loss will only be observed with the difference in the number of engine revolutions, since the work will be the same. Fuel consumption is largely dependent on aerodynamic braking and vehicle weight.

"Vehicle theory" refers to the existence of a formula for the road fuel consumption Qs, which reduces (read, neglects) the dynamic and rolling radius values. It demonstrates a minimal reduction in consumption (counting per milliliters) while reducing the dynamic diameter of the wheels. At the same time, it is also important to take into account the tire profile height, which on wheels of a smaller diameter can negate all the desire for savings if the new rubber is higher than the old one.

Profile width and its effect on fuel consumption

The wider the tire profile, the greater the fuel consumption, as the weight of the wheel increases significantly. This again requires more effort from the engine to move the vehicle. In addition to weight, the contact patch, noise level and, accordingly, rolling resistance also increase, which again negatively affects fuel consumption, requiring high costs.

In fact, fuel consumption is significantly affected by the kinematic rolling resistance coefficient, which increases with increasing section width and decreasing tire outer diameter, tire pressure and changes in tire design. Other ways do not provide significant fuel savings.