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Tyres: No more treading lightly

Tyres: No more treading lightly

With newer materials and technology, tyres are ever-changing in their sturdiness with technologies that allow them to run longer even with a puncture.

Given the amount of research done while purchasing a vehicle, customers need to be completely sure about the durability of the product. Of all the things that customers require of a car, the tyre is given the least amount of importance. OEMs are often left to figure out what is best for the passengers in terms when it comes to tyres. Safety is prioritised when buying a car, along with cost and then performance.

While brakes are often rendered as the safety system, the thought of attributing safety to tyres is a secondary one. A bulk of the tyres made in India and even abroad are natural rubber tyres or standard tyres. However, with the advent of synthetic materials replacing all natural forms of materials such as leather and metal in automotive applications, tyre companies are constantly researching and patenting newer raw materials for the structure of a tyre.

Of course, with standard tyres come the cost-effectiveness that Indian buyers are usually concerned about. The only change in these types of tyres seem to be the shift from tube to tubeless which is a benefit if the tyres need to be fixed.

Made out of hard compound rubber, standard tyres are cheaper and well favoured, with all Indian brands offering them for all OEM specifications. Not only is the cost a factor but also is the sturdiness to consider as the rubber compound increases the tyre life making it a good investment. Although not meant for rough conditions, they are perfectly fine in urban or semi-rural conditions. These types of tyres compromises on the handling and cornering capability of the vehicle, however it’s not noticeable at the city speeds. The tread on these tyres are designed to have maximum grip while reducing road noise and enables adequate dispersion of water on rainy roads. These tyres could be used in all climatic condition whether dry, wet, cool or hot.

For specifically dry terrains, another type of tyres with a soft compound rubber is used. Due its performance and cornering capacity mostly they are fitted onto sports cars. However, moist or wet environments render these tyres useless due to their lack of tread, which are the grooves on a tyre that help it to maintain traction. Also, the wear out rate on these tyres is faster than hard compound tyres.

Winter tyres generally have a larger contact patch with a bigger and more pronounced tread patterns. Hence there is maximum grip on snow and mud while using these tyres. These types of tyres generally come with tiny metal studs on the treads and cannot be used on normal road surfaces. These tyres are essential for driving on snow as they provide maximum grip while accelerating, cornering and braking on snow.

A combination of hard and soft compound tyres are used for off roading puposes or on SUVs. The tread marks on these vehicles are enormous for good grip on alternative terrains that have sand or mud. In urban conditions too, these tyres can thrive on uneven surfaces and potholes.

Natural rubber tyres are the most widely used, albeit with a combination of other compounds and materials. Sometimes they are used in combination with synthetic rubbers and elastomers such as styrene-butadiene copolymers. However, newer, sturdier materials are constantly being used.

New Materials

At Pirelli Tyres, where the company has over 5,800 patents worldwide, using new materials and derivative compounds becomes a necessity. Pirelli has been experimenting with materials like Kevlar and silica for their high-end customers such as BMW, Mercedes-Benz and Ferrari. Largely a European company, Pirelli does manufacture these alternative compound tyres for the Indian market as well.

“Kevlar was originally used in bullet-proof vests. Known for its strength and lightweight, Kevlar is instrumental in holding the air in a tyre when there is great amount of centrifugal force acting on it. This centrifugal force causes the tyres to expand when it runs at 250 to 300 kmph,” says Sanjay Mathur, General Manager, Pirelli Tyres India.

Kevlar is so far stronger than any other material or compound available, adds Mathur.

As Pirelli mainly has its operations in Europe, the company is interested in keeping to the environment norms prevalent in the region which are more advanced than other regions. For this purpose it is slowly trying to edge out carbon black and using more of silica or silicon oxide.

“Carbon black is derivative that comes from burnt oil. Evidently, the production process is not eco-friendly. Therefore, we are trying to use more of a compound like silica. In terms of performance too, silica is a better compound,” explains Mathur.

Despite the rise of materials like Kevlar and silica, synthetic copolymers are still constantly used. “With 5,800 new patents, we are constantly exploring new products and the derivative of several other polymers is going to come into it. However synthetic rubber will still be in use. While not being as advanced technology-wise, its usage goes makes up 15 to 16 per cent,” says Mathur.

In all of this, Mathur observes that natural rubber as a material would be very difficult to replace. “Natural rubber would be difficult to replace as it is very cost-effective and it still remains one of the most important component of a tyre. The other synthetic materials will still take time to gain popularity,” he says.

While new materials are explored in the tyre industry, companies are developing technologies to help them be more efficient in the game.

New technology

One of the first things that come to mind when driving a car is the fear of being stranded because of a flat tyre. A flat tyre often happens at the most inopportune moment or location. Because of this tyre companies are now trying to get their hands on the new run-flat tyre technology. At a lower, reduced speed, this pneumatic technology can allow the tyre to keep running even after a puncture. Of course the distance until which it can run is limited, but it is enough time to find a service station to get a new tyre. The tyre resists the effects of deflation with the help of a supporting system with specific reinforcements inside the walls. Originally these tyres were provided for heads of state or people with military protection. The objective for the same was to keep their tyres running even if they were shot and hit by bullets. Today, car manufacturers offer run flats so that they can save space and not increase the weight of the car by offering a spare tyre.

Run flat tyres made by Pirelli are used in custom vehicles like the newly launched BMW M5. “The latest tech that we have developed today are run-flat tires. A car can run for a distance of 80 km at the speed of 80 kmph despite a puncture and with no air in it. The tire’s sidewalls are heavily reinforced to support the vehicle when the air pressure is low or even when the tire has lost all its pressure,” says Mathur.

These tyres are beneficial for those that don’t know how to change a tyre themselves or are stranded in an unsafe location. A number of sports cars and luxury sedans have been using run flat tyres for many years now. The benefits include being able to drive on a flat tyre and even a tyre blowout due to its ability to support the vehicle without air. The driver can still be able to steer the car as normally as possible.

As this does not require a spare tyre to come with it, OEMs that custom-fit these tyres do not provide a spare or tools.

However, run flat tyres come with their set of cons as well. For one they are heavier than regular tyres and they have a hard ride. To counter this, tyremakers need to put in a softer tread compound on a run-flat tyre. A side effect of the softer compound is a shorter tread life. This means that the tyre needs to replaced regularly and is not as easy on the pocket.

Blowouts are still possible if a driver forgets to check the run-flat warning and drives beyond the zero-pressure range or above the speed limitation. The tyre can begin to disintegrate, with the same destabilising effects. They are also hard to find and there is less on-shelf availability of the same. Another side effect of the stiffer construction is that the sidewalls do not bulge if the air pressure is low. This means that it is critical to have a tyre-pressure monitoring system to check the pressure.

At the same time, while run flat tyres are gaining popularity, self-sealing tyres too are an innovative way of dealing with punctures at high speeds. The self-sealing tyre isn’t a run-flat tyre in the sense that it can operate without air. Instead, it has a layer of sealant inside the tyre that can maintain the air pressure in the event of a puncture. The tyres in this case have a sealing agent that sticks to the object that has caused the puncture which prevents the loss of air from the tyre. In case the object is removed from the tyre, it will pull a part of the sealing agent out with it which will take its place in the puncture, thereby completely sealing off the air.

“Punctures usually take place because of a sharp object like a nail getting lodged in the tread. Pirelli tyres have a chemical inside the tyre that can seal the hole if the nail that punctures the tyre is pulled out. Therefore that eliminates the puncture and you can continue to use the tyre without having to repair it at all,” states Mathur.

The biggest advantage of the self-sealing tire is that it resembles a traditional tire. It can be mixed and matched with standard tires and the tread life is the same. The downsides are the higher cost and lower availability.

However, a disadvantage of the self-sealing tyre is that any punctures or tears above 5mm cannot be sealed and the tyre will have to be replaced. Also the puncture that can be sealed should be near the centre of the tread. At the moment, Continental and Pirelli are the two tyremakers that produce self-sealing tires.

The noise from the tyres is one of the things that tyremakers aim to eliminate. A by-product of the friction created between the tyre’s surface and the road’s surface is the squealing noise that we hear. Although it has been possible in recent years to reduce the tyre noise and to enhance the ride quality to a certain amount, completely shedding tyre noise is impossible. And so, it is mandatory for anyone driving with a set of tyres on their wheels to be able to put up with the smallest level of tyre noise in all circumstances.

The primary reason is that the friction between the rubber and the road surface emits this squealing noise. With a tighter grip, a higher noise level is also expected. Another reason behind this is, when rolling at a high speed, air is pulled in and compressed between the tread grooves. This releases some noise as well. As a result, different types of tread designs will cause different levels of noise, for the groove pattern would differ between them.

Another factor leading to tyre noise is the chamber within the tyre. The void space inside of the tyre acts as a large resonant chamber, amplifying the noises arising within it.

Companies today are undertaking tyre noise with an intent resolve, and many of the premier tyre brands manage to engineer radials with the lowest noise emissions. Some tyre companies are designing their tread pattern in ways that makes the air compression noises cancel each other out. Specially designed grooves can reduce noise emissions by scrambling the sound waves arising from the air compression. An example is Bridgestone, which is already implementing this technology in many of its tyres. This is an innovative technique that many other companies are also beginning to employ today. Furthermore, some are designing tyre grooves in a manner that controls the noises bouncing underneath the car.

Pirelli has architectured an advanced technique to reduce noise emission to the fullest. Known as the PNCS, or the Pirelli Noise Canceling System. The inner lining of the tyre is imbibed with a strip of polyurethane.

“When we produce tyres there is a certain amount of oils that are used. To reduce the level of noise, Pirelli has created a technology that uses a derivative of non-aromatic oil, or another type of natural oil, in place of aromatic oils which are essentially crude oils,” explains Mathur.

Made as a spongy, noise absorbing material, this polyurethane consumes the noise bouncing within the large, empty inner air chamber of the tyre. As the spacious, empty inner chamber of the tyre is a primary cause behind the tyre noises experienced. As a result, this is a greatly effective method to gash out the most tyre noise possible.

Continental too has embarked on the development of tyre-noise reducing technology called ContiSilent. It is designed to reduce interior noise on all road surfaces. These tyres are equipped with an inner tire absorber, a polyurethane foam, attached to the inner surface of the tread area with an adhesive. Regardless of the temperature, the structure of the foam stays intact. These tyres help reduce interior vehicle noise up to 9 dB(A), depending on the type of vehicle, its speed and the road surface. The driving performance is not affected and there is no negative influence on mileage and load or speed capability.

Most of the tyre brands today help to bring the best ride comfort by asserting noise emissions as an active problem for their tyre designs, and using technology and innovation to bring the noise levels down as far as possible. Constant innovation and change is the only thing that can unleash the best potential in all inventions and products, and tyres are no exception in this regard.

“With 5,800 new patents, we are constantly exploring new products and the derivative of several other polymers is going to come into it.”

– Sanjay Mathur, GM, Pirelli Tyres India

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