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Goodyear Dunlop is developing a new tyre that will automatically maintain the correct pressure by Air Maintenance Technology (AMT)

Paolo Ferrini

For the moment at least, air is one of the things that drivers do not have to pay for. And yet, let's be honest, there are really very few people who regularly check their tyre pressures. The figures speak for themselves. A survey carried out in Europe in 2011 by Goodyear Dunlop revealed, for example, that 73% of the interviewees did not know the correct tyre pressures, that almost half did not know exactly the right time for checking tyre pressure (when the tyres are cold), and although 59% declared that they regularly checked tyres pressures, at least half admitted frankly that they would set off on a long journey without doing it. Negligence that is really dangerous because driving on tyres that have too much or too little pressure can be expensive, not to mention unsafe.
But in the medium-term something could change. Not only because drivers are beginning to realize that it's a mistake, but also because of the commitment of Goodyear researchers. At the laboratories in Akron (United States) and Colmar-Berg (Luxemburg) there is in fact a new tyre in an advanced stage of development that is able to maintain and automatically correct tyre pressures. Understandably, Goodyear is keeping the project under wraps, but what we can say is that at the basis of this innovation is the new Air Maintenance Technology (AMT), a special self-inflation system with a miniature pump located inside the tyre. Without doubt, this is a solution that would make vehicles safer and more efficient.
At the moment, Goodyear is not making any forecasts about when this new technology will be launched on the market, but confesses that the interest shown by the U.S. Department of Energy and by the European Union should contribute to accelerating development times.
The new Goodyear tyres could solve a whole series of important problems that go well beyond user laziness. Mileage, comfort, the transmission of traction and braking forces are all affected by tyre pressure. Insufficient pressure causes excessive flexion of the casing which, in its turn, causes excessive heating of the tyre and an increase in rolling resistance resulting in uneven wear. In extreme cases, insufficient pressure can damage the tyre. On the other hand, too much pressure can reduce mileage and cause uneven and rapid wear.
"Drivers frequently make three classic errors" - said Luca Crepaccioli, chairman and CEO of Goodyear Dunlop Tires Italia - "they do not check pressures before setting off, they check the tyres when they are hot (which gives an incorrect reading), or they inflate tyres without taking the weight of the vehicle into consideration. There is a distinct difference between an empty vehicle and one that is fully loaded".
To keep a vehicle at optimal performance levels (and in particular its grip on corners), tyres must always be at the correct pressure. Many problems begin with a gradual and undetected drop in pressure. "If tyres are not sufficiently inflated, the weight of the vehicle is all on the outside of the tread, which increases pressure on the tyre walls or shoulders, instead of being distributed evenly over the entire width of the tyre. This means that when the tyre is rolling, the walls heat up more than they should to the detriment of performance and safety" Crepaccioli continued. "With insufficiently inflated tyres, pressure on the ground is less evenly distributed so that the area of the tread in direct contact with the road is also reduced. These effects reduce grip and, especially if the vehicle is heavily loaded, can have a significant impact on driving behaviour. Braking distances are longer and the ability to take corners becomes less reliable and precise, which could lead to a loss of control".
In the space of three months, tyres can lose up to 0.2 bar of pressure simply because of the daily propagation processes in the tyre. "Too many drivers make the mistake of thinking that they can judge tyre pressures by kicking them or looking at them. You cannot see a reduction of 0.2 bar with a visual inspection. Some studies carried out in the European Union show that the tyres on over 64% of vehicles have incorrect pressures. The majority of drivers simply do not check tyre pressures often enough, with significant consequences for vehicle safety."
As we said, insufficient or excessive tyre pressures do not make use of the entire area of the tread. Not enough inflation increases wear on the outside of the tread and too much inflation increases wear on the inside of the tread. Both have a negative effect on mileage. Vehicle fuel consumption increases and drivers get fewer miles for a litre of fuel.
"Drivers must look after their tyres and all the other aspects of the vehicle that are important for safety. Tyre pressures must be checked regularly and, above all, before setting off on a long journey with a fully loaded vehicle" Crepaccioli concluded.

• Pressures always electronically controlled

An ever-increasing number of new cars are fitted (as standard or on request) with electronic devices for checking tyre pressures.
These devices can be direct or indirect. The former, known as Tyre Pressure Monitoring Systems (TPMS), have sensors inside the four tyres which are attached to the respective rims by means of a mechanical system; they are either balanced by a suitable counterweight or mounted inside the tyre valves. Indirect devices are often connected to the ABS and they detect any loss in pressure by measuring the rotational speed of the wheel (higher speed indicates a small circumference and therefore an insufficiently inflated tyre). This system, known as Deflation Detection System (DDS), is connected to the vehicle rather than the rim. Many cars are already fitted with pressure monitoring systems as standard equipment. They have been mandatory since 2008 for new vehicles sold in the United States and will be also in Europe from 2012.

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