Degradation of reference tyres used for CPX measurements

Measurements of tyre/road noise using the Close Proximity Method are based on reference tyres that are described in ISO/TS 11819-3. The standard specifies two tyres, namely "P1" and "H1" that should be used during measurements. To be used for measurements each tyre must fulfill certain conditions that are listed in the standard. The conditions are related to the tread pattern depth and rubber hardness. During experiments performed at the Technical University of Gdansk (TUG) two identical tyres of "P1" stored in very different condition types were periodically tested for hardness, tyre/road noise and rolling resistance. The paper describes results of the experiments that were carried out for nearly two years.