Re ECF Project: 2010-25

Project Title: Characterisation of low-noise tyres for the roads of Hong Kongt

Applicant: Dr. HUNG Wing-tat of Hong Kong Polytechnic University

Total Approved Grant: $1,072,069 (ECF & WWGF: 50/50)

Duration: 1/1/2012 to 28/2/2014

Project Status/Remarks: Completed

The project aims to use the newly designed and fabricated Close-Proximity vehicle to conduct a systematic on-road study on the acoustic properties of tyres in order to identify the measurable characteristics of low-noise tyres. These characteristics include a) tyre rubber hardness; b) tyre tread pattern; c) tyre tread depth; d) tyre pressure; e) tyre temperature.

Summary of the Findings/Outcomes:
This study on low noise tyres started with a market survey on the sales and usage of various tyres locally in Hong Kong as well as to record the characteristics of various brands and makes of tyres. 941 private cars, 175 HGV, and 37 taxies were surveyed. Most common brands of tyre with a carefully selected size and tread block patterns were selected for testing on one commonly laid road surface, namely wearing course (WC), and one low noise road surface, namely polymer modified friction course (PMFC) at 50 and 70 km/h to assess the characteristics of tyre/road noise generated under various singular and combinations of tyre and road factors. Over 30 new and old tyres with varying properties of rubber hardness, depth and sizes were tested; tyre/road noise, air and road surface temperature, tyre pressure and vibration data were recorded. In order to identify the tyre properties on tyre/road noise, over 500 runs on the roads were made. It was found that the bi-directional and asynchronous tyre pattern was the quietest on WC. The asymmetric pattern was the noisiest on PMFC. The tyre block size and distribution may also contributing factors. The tyre/road noise increased as the tyre rubber hardness increased owing to aging but decreased as the tyre tread depth decreased. Since minimum tyre tread depth was specified for road safety, it was not recommended to make further specification for tyre/road noise reduction in order to avoid confusion. The tyre size had very little effect on tyre/road noise. It is therefore not recommended to specify the tyre size in order to reduce noise. The major results were published in eight conference and one journal papers, presentations of research findings were made in five local and international workshops and conferences.