Tyre developers are constantly trying to keep up with customer demands and statutory regulations, not to mention doing battle with the laws of physics and chemistry. But while they may not be able to square the circle, the new family of hybrid tires family sees Continental come pretty close.
Andreas Härtwig runs his hand over the piece of black rubber lying on his desk, a section of the new Conti Hybrid HD3. “Look at the tread, it’s really slim,” says the equally slim man wearing a short-sleeved shirt. “That helps to reduce the rolling resistance.” Härtwig takes a red screw driver from his pen holder and uses it to open up a narrow sipe in the tread on the tyre section. “The moulded corners here improve cornering performance.” Siljana Lietz, who shares an office with Härtwig, points to another groove: “and the thin zigzag pattern here increases grip, even when it’s snowing,” she explains.
The two product developers for Continental Commercial Vehicle Tyres are clearly very proud of their new “baby” and they have every right to be, because the Conti Hybrid tyre family for trucks combines the best of both worlds. The tyres are ideal not only for long-distance, straight-ahead driving but also for goods delivery vehicles, where constant manoeuvring means the tyres are subjected to high levels of stress. On the highway, they can help to save fuel; in urban areas, they don’t suffer wear as much as “conventional” long-distance tyres.
Finding the right balance
Developing a high-tech tyre like this is no easy task. “It takes around four years from the initial idea to the production maturity stage,” says Siljana. “To begin with, we receive a challenge from our marketing colleagues: The customers in a particular region need a product with such-and-such properties. In the case of the Conti Hybrid, our challenge was to find the perfect combination of maximum mileage and minimum rolling resistance – a real brain-teaser for the developers. “We know what works in theory when it comes to optimizing individual properties,” says Andreas. “…but measures that reduce wear can increase rolling resistance. The challenge is to find the right balance.”
Essentially there are three key parameters that developers can tweak: the design of the tyre, the rubber compound for the tread strips, and the tread shape. Two teams – one focusing on drive axle tyres and the other focusing on steer axle and trailer tyres– started work on developing the new Conti hybrid family. The development of a tyre is subject not only to the input from marketing and the laws of physics but also to legal regulations concerning rolling resistance, durability, and noise levels. It took eighteen months to identify the optimum material mix for the new Conti Hybrid. Why so long? “We process anything up to 20 different substances in a rubber compound,” explains Siljana. “This gives us a myriad opportunities to find the perfect mix.” And every new variant needs to be tested both chemically and physically. And what about traction performance? Does the compound offer the right level of elasticity?
In parallel with the lab-based work, the right tread pattern is developed, initially on the computer. “We know right from the outset how many grooves a tyre needs on which axle,” says Andreas. “After all, we’re highly experienced in this field. It’s more about the details: Should we make 80 cuts or just 75?” Once the computer simulations have given us the answers we need, it’s over to the ‘tyre carvers’. Even though certain work steps can be performed by robots, we still need our specialists with razor-sharp knives and laser beams to carve out the computer-calculated tread pattern from perfectly smooth tyres. One carver can spend a whole day working on a single tyre to create an exquisitely handcrafted prototype.
Dreaming of the perfect tyre
However, the tests that the prototypes undergo – whether on test machines, in the lab, with X-rays, computer tomography, or as part of field trials on vehicles – take much longer. The prototypes are fine-tuned with ever-greater precision on the basis of the test results. When it came to the new hybrid tyres, for example, the development team thought long and hard about how the tread should be designed in order to reduce the amount of grit and gravel that gets stuck in the tires when the trucks travel along dirt roads. To the average person, one tyre may look exactly like another, but in a Continental tyre, even the smallest sipe is there for a reason.
The new Conti Hybrid family features Continental’s most recently developed rubber compounds. The tread, too, is particularly ingenious. However, the developers will not be resting on their laurels – after all, tyre development is an ongoing process. Andreas Härtwig, who has been a product developer for the past eight years, dreams of the perfect tyre. “When a new design emerges for the first time from a mould in one of our plants, that’s a really great feeling,” he says, with a grin on his face. “I offer all the help I can and make sure that everything is done exactly as we envisaged.” His colleague Siljana Lietz adds: “There is always room for improvement.” The trained mechanical engineer, who also has a doctorate in materials science, is already looking forward to the next generation of “Conti Hybrid” tyres– in another four years time.