Abstract
European Union Regulatory Framework on tires has produced regulations for tires sold within EU to help achieve the CO2 emission objectives set in EU for year 2020. Regulations EC 661/2009 and EC 1222/2009 aim to encourage consumers to acquire better tires by fuel-efficiency labeling.
The fuel-efficiency labeling of tires is determined by EC regulation 1222/2009 and the measurement method by UNECE Regulation 117 measured rolling resistance. This test is performed on a freely rolling tire, which doesn’t take into consideration transient driving situations and the differences of tires’ efficiency to deliver traction power to road. Therefore, currently tires’ fuel-efficiency label depicts mainly tires’ rolling resistance on vehicles freely rolling axle.
Methodology
This study was aimed to get a better understanding of tires’ influence to overall energy efficiency of a vehicle. In this study VTT has performed measurements on a chassis dynamometer in laboratory conditions with different tires in a given vehicle. Initial measurements were made with eight tires in 205/55R16 size, which is the most common tire size in modern passenger cars. After the initial study two tires were selected for additional measurements. The second tier study included alternations of the tire pressure, the weight of the rim, the width of the tire and the diameter of the tire. These alternations were made one by one, while other variables were kept constant.
Results
Results show, that besides rolling resistance, tires’ efficiency to deliver traction also affects to tires overall fuel-efficiency. It is seen, that the size and the weight of the tire has also an impact on vehicles energy efficiency. This paper describes the used test methods and the key findings within this study.
Limitations of this study
In this study the tire rolling resistance was measured only with an in-house test method using a chassis dynamometer.
What does the paper offer that is new in the field including in comparison to other work by the authors?
This study provides a novel approach for studying of tire rolling resistance influence to vehicle energy consumption.
Conclusions
Tires have a major impact on vehicles tractive resistance and therefore to overall energy consumption of a vehicle. Albeit the EU’s fuel-efficiency labeling of tires improves this knowledge among consumers, current tire test method alone is inadequate for comprehensive energy efficiency estimation.
KEYWORDS – tire, rolling resistance, test methods, energy efficiency, chassis dynamometer