Wet traction
Wet traction and rolling resistance tests were carried out by Prüflabor Nord. They followed UNECE Regulation No. 117, which is used in determining European tyre label ratings. Essentially the same regulation is used in other countries with tyre labels such as Japan, Korea, Brazil and soon also China.
In a typical dynamic-mechanical analysis (DMA) of tyre compounds, the glass transition temperature (Tg) of oil affects rubber behaviour. Higher oil Tg leads to higher tan delta at 0°C. This in turn is the most common wet traction indicator: the higher the tan delta, allegedly the better the traction. Aromatic oil (DAE) and RAE with higher Tg typically yield 5-15% higher tan delta than other tyre oils such as TDAE and naphthenic oils. Correlation of tan delta with traction, however, is not perfect.
Wet traction results are presented in the chart below. Tyres were compared with a 16” Uniroyal reference tyre (SRTT), and breaking results were indexed. It was found that the four tyre specifications tested yielded very similar indexes. Considering the deviation in the test, wet traction of each tyre specification was equal. Although the RAE compound had 10% higher tan delta, it did not result in better traction.