Over 20 per cent difference in braking distance between Winter Tyres and All Season Tyres Nokian Truck Tyres arranged a test event in Ivalo to test the behaviour of new winter tyres and new All Season tyres that are typically used in Central Europe and their differences under winter conditions. The event was arranged in co-operation with Liikenneturva (Central Organisation for Traffic Safety in Finland), Scania, PNO, the University of Oulu, and Oulu Vocational College. Based on the test results, the difference between the winter tyres and the All Season tyres was over 20 per cent in favour of the winter tyres in terms of both braking distance and acceleration. The test conditions were very wintery, as the temperature varied between -16 and -27 degrees Celsius during the event. Broadly speaking, the lower the temperature falls the smaller the differences between the tyres become as the friction of the surface increases. If the test had been conducted during the most slippery and demanding conditions at temperatures near zero, the differences between the tyres would most likely have reached over 30 per cent. The tests used two similar semi-trailers with new Scania trucks. One truck and trailer combination was equipped with the new Nokian Hakkapeliitta Truck F winter steer tyres and the new Nokian Hakkapeliitta Truck E winter drive tyres. The tyres on the second truck and trailer combination were new, typical European All Season tyres. The tests focused on braking distances, acceleration, and the handling of the truck and trailer combinations during double lane changes. Increasingly varying and demanding winter weather presents challenges for heavy vehicles The Hakkapeliitta Test Experience of 2013 was a continuation of the previous year’s event that tested the differences between new and worn tyres. The purpose of these test events is to improve the safety and efficiency of heavy vehicle combination by paying attention to the tyres fitted on the vehicles and their significance in terms of overall handling. Furthermore, the intention is to provide operators with researched information concerning the properties that make winter tyres for heavy equipment safe and effective even under demanding conditions. This type of research is also very important when considering the basis for winter tyre regulations on heavy vehicles. – We want to use test events in order to promote traffic safety and productivity for heavy vehicle. We require more versatile research information on the subject in order to make the winter tyres on heavy combinations even safer, says Teppo Siltanen, R&D Manager for Nokian Truck Tyres. In addition to safe driving, winter tyres that can ensure excellent grip on icy and snowy roads are essential for fluent and efficient transport under demanding winter conditions. Rapidly changing, demanding winter conditions have always been a part of Northern winters, but in recent years, winter conditions have become increasingly common throughout Europe. The more demanding conditions have caused many surprising situations in European traffic over the past few years, and that means that more attention should be paid to tyres everywhere in Europe. Differences of over 20 per cent in average braking and acceleration distance In the braking distance tests, the truck and trailer combinations performed braking from different starting speeds. The average difference in braking distance between the different truck and trailer combinations was over 20 per cent in favour of the winter tyres. The road surface also greatly affected the braking distance, as the distance on packed snow was over 30 per cent shorter than on polished snow in the middle of the lane. Based on earlier tests, this difference in braking distance will cause a collision at a speed of over 35 km/h with the worse tyres. In the acceleration test, the difference between the combinations was also above 20 per cent on average. The more snow the road surface has the larger the differences in acceleration distances become. When reviewing the results of the acceleration test, you should also note that the same tyre characteristics are important when the vehicle is setting off or climbing a hill. Higher grip on the driving wheels ensures that the vehicle can move and climb steep hills even under slippery conditions. In recent years, heavy snow storms have been experienced throughout Europe, and heavy vehicles have been stuck on steep hills and intersections when trying to set off again. This slows down traffic, causes traffic jams, and may even lead to accidents. Tyres that operate flawlessly under the most severe winter conditions are an absolute requirement for the timely and safe operation of transport. Good winter tyres also work in surprising situations In addition to the braking and acceleration tests, the test event also featured double lane change tests. The highly experienced driving instructors from Oulu Vocational College, who drove the truck and trailer combinations, gave their first-hand comments after the test. The drivers alternated between the vehicles during the tests, allowing both of them to gain a feel for both tyre sets. According to the drivers, the winter tyres made it easy to drive around the track and to keep the truck and trailer combination in the middle of the road. The driving feel was good, although the good grip did make movements somewhat sharp. With the Central European All Season tyres, the combination felt more slippery and loose. Driving this truck and trailer combination required special care and a carefully selected driving line. The truck and trailer combination equipped with All Season tyres was also problematic in cornering. Here, the grip of the driving wheels is especially important in order to prevent the vehicle from jack-knifing due to a sudden steering movement. All in all, good winter tyres were reliable even when it was not possible to anticipate everything and quick steering was required. - Based on test results from two years, we can say that the selection of tyres can have a significant effect on the driving safety and productivity of heavy vehicle combination. Very often, special [...]
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