Test tyres equipped with the most refined electronics, laboratory chemical analyses, x-ray images, and even computer tomography: Continental's testing methods for developing the perfect tyre are becoming ever more sophisticated and feeding our favorite colleague – the computer.
Rüdiger Menz looks through the iron bars on a green machine as tall as a person. It looks like an oversized washing machine. In the center, a thick wheel is turning on a drum. "This is where we measure rolling resistance," he explains. "It is especially important for a tyre's energy efficiency." The athletic Rüdiger quickly strides into the next testing room. In one corner, a steel drum 1.7 meter in diameter rotates behind thick safety glass. It is turning four mounted truck tyres at once. "We let the tyres run until they start to break apart" he says. "We are testing to see which conditions the different kinds of tyres can withstand and for how long."
Rüdiger Menz is the head of the expert field endurance evaluation. He is responsible for the test method development for tyre endurance at Continental. And he is tackling one challenge: Continental tyres last so long. "Some can run for a million kilometers. If we were to test the tyres in the field, a tyre would have to run for years so we can reproduce its entire life cycle.” Today, the test tyres run on our own vehicles and on the truck fleets of partner freight companies. And Rüdiger and his colleagues are working under intense pressure to come up with procedures to speed up tyre testing.
Hungry for data
Computer simulations produce the fastest results: What effect does a harder rubber compound have on endurance performance or rolling resistance? Do jagged grooves on the tread pattern increase driving safety? Our colleague the computer calculates the results in just a few hours. But for the results to be reliable, the calculation formulas have to be correct. And that can only happen when they are fed with data taken from real-life testing. Take one of the drum tests in the research and development hall in Hanover-Stöcken for example.
Here, individual truck tyres are subjected to a load of up to ten tons. "A drum test is performed under extremely precise conditions," says Rüdiger. "Which is why this method also produces extremely accurate data. The drawback: You can only test one load characteristic at a time, like a specific load, a specific temperature, or a specific air pressure." The test results of various factors must then be calculated together – difficult to do with all the interactions. Yet high-end tyres from Continental must still satisfy all the requirements at the same time when on the road.
Field tests on the road may take a long time, but they are still necessary. The testing team incorporates refined measuring instruments into the tyres, which record temperature development for instance. In hotter regions, for example, tyre temperature is an especially important factor to take into account when assessing tyre durability, explains Rüdiger Menz. Small holes are drilled into the tread pattern for the measuring devices – by remote control in the X-ray chamber. It's a question of tenths of a millimeter. X-rays also help us rapidly monitor the construction of test tyres. And they show us any "internal injuries".
Testing methods are becoming ever more sophisticated. Continental premium tyres perform to such an extraordinarily high level that simply looking from the outside with the naked eye doesn't get us very far. This is why sections are cut out of test tyres that have been driven and then chemically examined in a laboratory. Using Computer tomography (CT) allows minute details such as changes in tread depth to be analysed with pinpoint accuracy.
And the in-house CT equipment runs around the clock. The research and development team virtually dissects hundreds of tyres per year into thin, mm-wide layers. Scanning a complete commercial vehicle tyre takes about 24 hours – sliver by sliver. This yields valuable data – which can then be fed into algorithms for computer simulations. This is where Rüdiger Menz thinks the future lies. "By continuing to refine our measurement and testing procedures, we are getting ever closer and closer to our goal: virtual trials that are as short as possible and can accurately demonstrate real tyre performance." Speed is particularly important when it comes to developing new tyres. Because whoever slows down falls behind the competition.
"In recent years, we've become twice as fast at getting product ideas out on the road," says Rüdiger Menz as he types columns of digits into his computer. It's clear to see that Rüdiger Menz, who has a doctorate in mechanical engineering, enjoys building mathematical and physical models. "Our team embodies the spirit of invention" he beams. "We are doing pioneering work with the endurance models we are developing. We are at the intersection between theory and practice. We research, hone our testing methods, write programs – and always feel really close to the product." The tyre in the green "washing machine" keeps turning and turning.