Effect of retreading on rolling noise of truck tyres

We studied the rolling noise of 30 truck tyres on four different road surfaces, TSL8, DAC16 (grinded), ISO10844 and SMA11. Tests are performed under coast-by conditions at speeds between 40 and 80 km/h. Both SEL and LAmax values in one-third-octave bands are recorded at the standard positions on 7,5 m distance and 1,2 m height. A height of 3,0 m was added. We also recorded narrow band spectra close to the tyre. The tyre set comprises 10 steer types, 10 traction types and 10 trailer, 24 of these are original tyres, 6 are retreaded. In 5 cases both the original and retreaded version are tested. From all test tyres, the tread profile, the tread rubber hardness and the tread mobility is recorded. Some general results were published in Euronoise 2015. From this extensive data set we selected the data sets of the five identical tyre sets that were tested in both the original and retreaded version. The coast-by levels, both total A-weighted and one-third-octave spectra are compared on all tested road types. We observed in general an increase in coast-by values, but with varying spectral distribution of the effect. From the spectral differences possible causes of the observed change will be identified. This will be commented with the measured tread pattern geometry, tread rubber hardness and tread mobility spectra. Finally the implication on the effectiveness of the present type approval schemes will be sketched.