Tire-Pavement analysis toolkit to standardize Rolling Resistance and Grip measurement tests
In comparison to conventional tires, the low rolling resistance (LRR) tires often have higher prices, shorter mileage life, reduced wet and snow grip performances, and depending on the target market fuel saving much lower than their published values. However, they can also be extremely cost-effective in fuel economy and environmental impact. Studies suggest that LRR tires could result in a potential fuel savings of 4-11% and similar reductions in gas emissions. However, many organizations, experts and consumers have expressed concerns about the end benefits of LRR tires. Performance of LRR tires is usually presented using rolling resistance coefficient (RRC) parameter, which may not be accurately measured. Moreover, standard rolling resistance (RR) and grip tests regulated by ISO and SAE are performed on different surfaces, hence, resulting in errors in RR due to the influence of the micro- and meso-roughness of the pavement. A toolkit is proposed to estimate the realistic performance of the tires marketed as 'LRR' over their conventional counterparts with respect to different road surfaces. A comprehensive procedure for standardizing RR and grip tests with respect to micro-texture and tire wear rate will be presented. A correction factor to the current RR and grip measurements will be developed based on pavement surface and tire material. The project focuses on micro-to-meso scales interactions in material-pavement contact profile, and bridges that to the existing models on macro-scale performance of tires. The proposed toolkit will assist tire and pavement engineers in (i) analyzing the trade-off between pavement grip and RR and (ii) instituting pavement surface mix design for different traffic conditions, thus allowing road surface optimization.
Unrealistic expectations and lack of factual data on performance of LRR tires significantly limit the public adoption of LRR tires. While tire manufacturers are already emphasizing the significant of fuel reduction (sometimes up to 25-30%) by using LRR tires, customers often get less than 10% fuel reduction, which is sometimes accompanied by loss in grip and tire durability. On the other hand, Federal studies indicates that gasoline use would be dropped by 4% if all the replacement tires sold were LRR tires. To promote public trust on LRR tires, the proposed toolkit will provide consumers and fleet managers with adjusted RR and grip performance ratios, based on average road conditions in the target market. This will provide DOT with the needed information to encourage the adoption and use of LRR tires.
Michigan State University
May 10, 2017
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