Text: Marc ALIAS
Photos: Marc Alias and DR
With more than 900 million vehicles worldwide and the double expected within twenty-five years (!), The pressing need to save non-renewable fossil resources and above all, the preservation of our fragile health also requires the use of tires with low rolling resistance. As for the planet, it has seen others and will recover once again, but what about us? On the strength of this observation, most manufacturers are also going in the right direction. Starting with Michelin, a world pioneer in low-consumption tires. Accompanied by less polluting manufacturing, these tires, as rational as they are delicate to develop, seem to have succeeded in reconciling the irreconcilable. With the current advent of the 5th generation, now is the time to take stock of this success story…
1- Tires with less resistance to travel ...
... rather than green tires since some readers think that they come from recycling or are really this color (It exists)! All this is not a sight of the mind or an umpteenth marketing trap and it deserves to be underlined! Have you ever pushed your vehicle into your garage and worse, with a flat tire? On these occasions, you have been able to physically experience this famous resistance to advancement, very aggravated by the puncture or even under inflation. Indeed, let us recall once again that with a deficit of only 1 bar of pressure, one causes not only a great insecurity with a real risk of bursting but also an overconsumption therefore an over pollution of 3%. As such, we cannot highly recommend the installation of 4 clever K-pressure plugs with optical direct reading patented by Pirelli.
Let’s close this practical parenthesis and continue our point: even under optimal conditions, this loss of energy is equivalent to climbing a constant fictitious slope of 1%. In other words, 20% of the energy consumption necessary to drive a motor vehicle thermal or electrical is lost in tires. Worse, from one full in five, we go to one in three in the case of heavy goods vehicles or an electric vehicle in urban use! However, between the best and the least gifted of competitors, internal Michelin tests revealed differences of up to 50% of this resistance.
Since 1992 and the first generation of Michelin Energy tires, currently all manufacturers, including Bridgestone with its ECOPIA series, have offered a range of "green" tires. As with "clean" cars, this misleading term is overused in the traditional media, which is still as incompetent in technology. That said, it applies quite well in the particular case of the patented Goodyear BioTred for its gum mixture based on corn starch, instead of silica, which also has (very!) Elastic qualities which reduce tire rolling losses. This project is even supported and subsidized by the EEC within the framework of the global European environmental project LIFE of more than 12 million Euros in total.
The origin of rolling resistance is a unfortunately unavoidable physical phenomenon that appears through the grip cone dear to my students in STI technical terminals. This theory provides that the maximum tangential traction or braking force is proportional to the weight supported by the wheel and to the coefficient of adhesion, f, which must be as high as possible to ensure this ... precisely! As is the case for rolling resistance, this challenge is a real Chinese puzzle. If engineers cannot therefore reduce it to zero, at Michelin, we predict an additional drop of 25% in the ten years to come.
Today, various levers can act on these losses more and more independently of the other characteristics of the final tire: there lies all the know-how of the famous manufacturer! Thus, at design time, the materials, i.e. 200 different components on average, and the structure have the same influence on the rolling resistance while an increase in the depth of the tread patterns by 50% degrades this performance by 12%. In the same vein, a large wheel diameter will have a positive impact unlike the speed index…
Michelin, the great precursor ...
For the first generation of Energy tires in 1992, labeled "Green X", Michelin had successfully increased the percentage of silica in the rubber compound. On this subject for 20 years, it is therefore clear that its research and development department, with an annual budget of more than 500 million euros, has acquired an incomparable advance, experience and expertise! This is why, in addition to the range for private vehicles, Michelin has also developed no less than 3 successive generations intended for heavy goods vehicles.
In a constant concern for improvement, the second version appeared in 2 with an envelope that heats up as little to reduce fuel consumption while being able to heat quickly but locally at the level of contact of the rubber with the road. This last quality, still current, makes it possible to offer short braking distances even on wet ground. According to the graphics of the famous manufacturer, successive generations have brought a significant improvement in grip before reaching the balance of the current Saver. In 2003 years, the more than 3 million units sold at the end of August 38 have saved more than 2010 million liters of fuel, i.e. 136 t of CO273 or the equivalent of 000 cars that would have driven without any release of carbon dioxide! To crown this achievement, it also obtained nearly 2 technical approvals from the largest car manufacturers on the planet!
But, in a general context more ecological than ever, all the major manufacturers are asking for fuel savings from all their equipment manufacturers. Between 2012 and 2018, European penalties will directly tax manufacturers whose new cars exceed certain thresholds of CO2 emissions according to the following scale and per unit sold:
- up to 1 g of excess: € 5
- Between 1 and 2 g of overshoot: 5 € + 15 € / g for the fraction of overshoot beyond 1 g.
- Between 2 and 3 g of overshoot: 20 € + 25 € / g for the fraction of overshoot beyond 2 g.
- Beyond 3 g of overshoot: 45 € + 95 € / g for the fraction of overshoot beyond 3 g.
- From 2019: 95 € / g.
The percentage of vehicles taken into account for the calculation of the average emissions of each manufacturer is progressive: 65% in 2012, 75% in 2013, 80% in 2014 and 100% from 2015.
(Source: Regulation 443/2009)
In addition, from November 2012, another European regulation will impose an informative label at the time of the sale of the tires. It will inform customers about 3 essential qualities which are:
1- fuel economy
2- the braking level on wet surfaces
3- the outside noise level while driving
Note that if a tire could not meet one (or more!) Of the 3 minimum performance thresholds required, it would be prohibited from sale. It is estimated that 30% of the tires currently on the market will be withdrawn from the market in 2014!
Saver 5
Historically linked to Citroën, the Clermont-Ferrand manufacturer has reserved the world premiere of the 5th generation of its famous Energy (or Saver) series for the new C4 unveiled at the 2010 Paris Motor Show. an average gain of 5 g of CO2 instead of 4 previously. Since Citroën has been using Energy Saver tires, the two companies estimate the savings at nearly 30 million liters of fuel and therefore 72 t of CO000.
Logically, it will retain its excellent reputation for mileage, which remains one of the strong points of this range and of the brand in general.
To be more complete, here is a bonus, an interview with M.Menendès Pierre, director of technical communication at Michelin carried out during the presentation of the previous generation Saver and still current.
MA: »Why and how have you been working hard for almost 20 years on this delicate problem, yet little known to customers? "
MP: »This thorny problem, which represents 20% of the consumption of light vehicles and more than 30 for heavy goods vehicles, can be resolved by our engineers by playing on the nature of the materials that make up the rubber of these Energy tires. Reducing fuel consumption means reducing pollution and spending for our customers! For over fifteen years, our more than 4000 research and development specialists have been working to reduce their hysteresis, that is to say the difference between the energy absorption of the tire and its return to the road. Of course, this difference should be as small as possible. We are coming to this improvement by replacing, in particular, the carbon black fillers with silica which makes our rubber much more elastic, therefore less plastic and less dissipative of energy. This approach makes it possible to preserve the adhesion properties, or even to improve them on wet ground, while reducing the friction on the ground for consumption gains of the order of 3% or 2 to 5 g of CO2 / km. Another advantage, these tires allow on average 25% more kilometers than their competitors. Note also that we have particularly collaborated with Peugeot for its 308 HDI which is fitted with the fourth generation of Energy Saver tires as standard. Peugeot has made a considerable effort to reduce consumption, so the rejection of C02 and Michelin tires were an important and immediate contributor. ”
MA: “We can also think that thanks to your synergistic efforts, the new Citroën C4 will make less than 140 g CO2 / km (110 to 127 produced, ndla) in order to benefit from a divided company vehicle tax (TTVS) by two. By the way, what happened to the promising Proxima tire presented at the 2006 Geneva Motor Show?
MP: »I remind you that this was a prototype study of tires with very low rolling resistance, inflated to 3,5 bar to reduce its deformation and not intended for direct marketing in Europe. That said, we have used the many lessons learned during its development for the 4th and 5th generation of Energy tires coming soon. Thus, we were able to optimize the operation in the rubber area in contact with the ground under various driving conditions in order to further improve the grip despite the new reduction in rolling friction! Another area of progress, we have reduced its mass by 10% in order to reduce power losses during acceleration, braking and even stabilized! "
MA: “Logically, given the increasing price of fuels, just like the masses of modern vehicles, these optimized tires should be generalized as much as possible! What is the share of Energy tires in your current sales? "
MP: »It now accounts for more than 75% of our sales in Europe for light vehicles and we can predict a further increase thanks to the imminent release of the new Energy generation. In terms of commercial vans, our Energy range is the most efficient on the market and heavy trucks equipped with our A2 Energy see their fuel consumption drop by up to 6%, which is essential on average consumption of l35 L / 100 km. Likewise, our X One, which replaces twin tires, improves payload and stability while reducing consumption by up to 8%. Of course, this approach to reducing rolling resistance applies globally to other influencing factors with, for example, monitoring and active control of the inflation pressure continuously. Truckers will gain autonomy, performance and profitability. Finally, these tires have a longer lifespan than conventional tires, which makes them doubly profitable. Finally, be aware that Michelin, within ETRTO and the Rubber Manufacturer Association, campaigns for clear information for customers. They will thus be made responsible at the time of their choice by an energy index linked to each tire, in the same way as the energy label applied to all new vehicles under concession since early 2006, in France. ”
MA: "Regarding responsibility and to broaden the subject, how will Michelin respect the standard for manufacturing tires without volatile organic compounds (VOCs) which will be mandatory at the start of 2010? "
MP: »Our brand is continuously working on this in the general interest. However, this positive development must be done without any compromise on the overall performance of our products. Our laboratories have already validated a new manufacturing process without using aromatic oils. This will be generalized in all our manufacturing by the application of this new standard, in January 2010. In addition, there are other areas of confidential improvement on which our research and development teams are currently working since Michelin reinvests almost 5% of its turnover each year. "
With the inevitable increase in the price of fuels in the short and long term, it is inevitable and desirable that the classic automotive world also make its revolution or disappear. As such, these "green" tires will also be at stake in a fierce battle between manufacturers, or ultimately, the customer will emerge victorious ...
Photos and diagrams:
Here at the last Mondial Auto Porte de Versailles, Michelin presented the fruit of almost 20 years of RetD with the arrival of its 5th generation Saver. A range that is still as attractive as it has successfully achieved the feat of reducing parasitic resistance to advancement without degrading, on the contrary, the other performances of the tire!
Here Michelin has made an inventory of the main parasitic forces that oppose the advancement of a vehicle. Of course, depending on the type of traffic, highway, road or urban, their share varies greatly. Thus in town, rolling resistance is double (30%) of losses on the highway! Copyright Michelin
During the press conference, Michelin tried to make journalists who were rather incredulous understand that the squaring of the circle was well on the way to being achieved thanks to the Energy Savers, which was brilliantly proved by 2 tests carried out before our eyes. and those of the two bailiffs present…
Whether in terms of the braking distances in the wet carried out by the journalists present or the comparative consumption test between conventional competitor tires and the Michelin Savers, the results are all positive! These objective results have been officially certified by the 2 bailiffs appointed by Michelin…
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Here is a graph that clearly shows the progress made by Michelin since the origin of the brand: rolling resistance has been divided by more than 3. Note the two major innovations with the advent of radial in 1946 and the introduction of the silica in the 1st Energy generation in 1992. The 4th arrived in early 2008 under the evocative name of Energy Saver and the 5th evolution gradually followed in 2011… Copyright Michelin
This demonstrator running in 195/65 R15 will remain a prototype despite fuel economy qualities slightly higher than the current Energy ranges. That said, a production tire is always a compromise and it cannot be marketed if some of its qualities as crucial as grip, were sacrificed on the altar of fuel economy, for example. Strongly the 5th generation Energy Saver range at the start of 2011, which will inherit the latest Proxima innovations, notably an almost identical economy! Copyright Michelin
Here is a rare photo of the Michelin research and development center. A technician measures the rolling resistance of a tire using this specific rolling machine. You might think that the next Energy Saver tire will still be there when you read these lines ... Copyright Michelin
Also at the Michelin research center, a power bench is used to measure transmission losses, including the share of tires, during deceleration. Here a Peugeot 307 which has certainly given way since, to the 308 HDI 90 cv equipped with Energy Saver to stay under the fateful barrier of 140 g / km of CO2. Copyright Michelin
At Goodyear, we took the expression "green tires" to the letter with the patented BioTRED technology. This resides in the introduction during its manufacture, of a corn starch extract instead of certain petroleum derivatives and silica, in particular. Not only can GT3 tires save you up to 5% in fuel, but they require less as soon as they are made!
Michelin has always been emulated: Bridgestone has since 1999, a green range called Ecopia with the same stated objectives. Here, the new compound of Nano Pro-Tech rubber combined with a new design of the sculptures promises 3% savings in consumption…
Kpressure: An essential complement so as not to spoil the meritorious efforts of manufacturers of low rolling resistance tires, Pirelli has created these plugs for monitoring the optimal inflation pressure. Available in 13 calibrations between 1,8 and 3 bars, their sensor with an accuracy of +/- 0,025 bar (!) Will signal the natural pressure drop of 0,2 bar every 3 months by changing from white to red and this, from 10% fall. Knowing that an under inflation of 20% increases the tire wear by 25% and the fuel consumption by 3%, these smart caps are not a gadget! Ditto on a motorcycle ...
Indeed, you have not understood everything, so read again because it is not yet SIA or bac + 5 level !!!
This is very good and the low resistance tires are a real technological advance adopted by manufacturers because it reduces the polluting emissions of their vehicles.
