Studded tyres greatly reduce skidding and accidents on snow or ice covered roads. However, all too often the studs come into contact with the road surface. The use of studded tyres is very costly in terms of annual load wear. Additionally, as the studded tyres wear the pavement they eventually cut ruts in the road that can fill with water to create a hydroplaning hazard in wet weather. A further issue is the polluting dust that is created. The Prall Test (Method A) has proved to be the most successful way to investigate abrasion due to studded tyres. At the same time reproducibility has been an issue. At Cooper we have assessed the aspects of the test crucial to performance and improved them, via the fitment of a second test chamber, thus significantly reducing variability.
The CRT-PRALL is designed to carry out the Prall Test according to EN12697-16 Method A in which a cylindrical specimen of asphalt having a diameter of 100mm and a length of 30mm is tested at a temperature of 5°C. The specimen is worn by abrasive action over a standard time period of 15 minutes by 40 steel spheres. The loss of volume in millilitres is recorded and reported as the abrasion value.