Influence of rolling resistance on CO2
The 9th meeting of the informal subgroup on the development of the WLTP test procedure (WLTP-DTP) (16–18 April 2012, Bern) included a discussion of whether, and how, the selection of tires should be implemented in the test procedure. One of the proposals was to link tire selection to the combined vehicle test weight proposal, the current version of which is described in document WLTP-DTP-10-02. The idea was to select, from the range of tires on offer for the vehicle model, a tire in the worst rolling resistance class for the vehicle with the highest test mass, and a tire in the best rolling resistance class for the vehicle with the lowest test mass.
This led to some discussion on the influence that rolling resistance could have on the slope of the CO2 versus mass interpolation line. The ICCT offered to provide input on the influence of rolling resistance on co2 in order to make a well-informed decision on this issue. in the WLTP-DTP Subgroup on Lab Process&mdashInternal Combustion Engines (LabProcICE) meeting on 22 May 2012 in Brussels, it was agreed to leave tire selection out of the combined vehicle test weight proposal.
Still, there were some concerns (mainly by the Japan Automobile Manufacturers Association) about the width of the tire labeling classes in terms of CO2, which led to their proposal that the worst-case tire from the worst rolling resistance class should be tested. The intent of this paper is to quantify the expected effect of tire classification on CO2 as input for the discussion on tire selection.