BKT Tires: the Weight of Quality
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Apr 21, 2022
JATMA Study: Reducing CO2 Emissions by Reducing Rolling Resistance in Tires
… When considering CO2 emissions throughout the entire life cycle of tyres (raw material procurement, production, distribution, usage, end of life and recycling), more than 80% of CO2 emissions is accounted in the usage stage. Reducing the tyre rolling resistance improves vehicle fuel efficiency, which can reduce CO2 emissions.
In 2010, the Japanese tyre industry started the tyre labeling system applicable to replacement summer tyres for passenger vehicles ahead of all other countries in the world. General users can select fuel-efficient tyres1 with low rolling resistance while referring to the grades shown on the labels when they purchase tyres.
Tyres with lower rolling resistance have become more popular year by year thanks in part to this labeling system. JATMA conducted a survey to confirm the effect of reducing CO2 emissions through the widespread use of tyres with lower rolling resistance and published the results in 2015 and 2018. CO2 emissions were calculated for 2006, 2012 and 2016, before and after the labeling system started.
After that, we determined to conduct this kind of survey once every four years considering the product life cycle and other factors. This time, we summarized the CO2 emission reduction effect as a result of a survey of CO2 emissions in 2020.
Note 1: Tyres for which the rolling resistance performance is classified as A or higher and for which the wet grip performance is classified as a, b, c or d
(Refer to https://www.jatma.or.jp/english/environment_recycle/aboutlabelingsystem.html)
Status of reducing tyre rolling resistance coefficients
Fig. 1 shows the rolling resistance coefficients of tyres that the member companies sold in Japan.
The charts show the ratios of the numbers of tyres sold according to the grading in the labeling system (Table 1).
The ratio of tyres classified as A or higher (tyres with rolling resistance coefficients applicable to fuel-efficient tyres) accounted for 29.7% of total sales in 2006; the ratio increased to 54.7% in 2012, 76.9% in 2016 and 77.8% in 2020. Thus, the sales ratio of tyres with lower rolling resistance has been continuously increasing. The ratio of tyres classified as AA or higher was 3.8% of total sales in 2006; it increased to 9.7% in 2012, 28.5% in 2016 and 38.3% in 2020.
Table 2 shows the average values weighted by the number of sold tyres for each tyre rolling resistance coefficient (RRC) level. The value in 2020 decreased by 0.2 N/kN (2.4%) from that in 2016 and decreased by 1.56 N/kN (15.9%) from that in 2006. Thus, the weighted average RRC has been continuously decreasing.
Note:
This survey targeted original equipment tyres and winter tyres that are not covered in the labeling system to evaluate CO2 emissions of all types of passenger car tyres.
Table 1 Tyre rolling resistance coefficients (RRCs) and classifications in the labeling system
| RRC Unit：N/kN | Classification under JATMA labeling system | |
|---|---|---|
| RRC≦6.5 | AAA | Fuel Efficient tyres |
| 6.6≦RRC≦7.7 | AA | |
| 7.8≦RRC≦9.0 | A | |
| 9.1≦RRC≦10.5 | B | ― |
| 10.6≦RRC≦12.0 | C | |
| 12.1≦RRC | （Lower than C） | |
Table 2 Weighted average RRC (N/kN)
| 2006 | 2012 | 2016 | 2020 |
| 9.80 | 9.06 | 8.44 | 8.24 |
The Reduction effect of CO2 emissions when tyres are in use
①Based on Tyre LCCO2 Calculation Guidelines Ver. 3.02 issued by JATMA, CO2 emissions per tyre when tyres are in use3 were calculated from the rolling resistance values in Table 2. The value in 2020 was 196.6 kg/tyre. The CO2 emissions decreased by 4.8 kg (2.4%) from those in 2016 and by 37.2 kg (15.9%) from those in 2006 (Fig. 2).
Note 2:(https://www.jatma.or.jp/environment_recycle/globalwarming.html) In this survey, the emissions in the past fiscal years were calculated based on the new guidelines (revised in March 2021), so the values differ from those published in the past.
Note 3:
Emissions throughout the entire service life of a single tyre. The calculation conditions (e.g., fuel economy and tyres’ contribution to fuel consumption) are not the average market values. They are the values measured on the vehicle in JATMA test and values calculated with those.
②Since it is difficult to accurately determine the amount of CO2 emissions during tyre use in a year, the total amount of CO2 emitted by the end of service life of the tyres sold in the year is used as an alternative indicator for comparison. The CO2 emissions in Fig.2 is multiplied by the number of tyres sold in each year to calculate the total CO2 emissions in the Japanese market.
CO2 emissions in 2020 were reduced by 2.825 million tons compared to 2006 as the effect of rolling resistance reduction (Fig. 3).
Although CO2 emissions per tyre have been continuously decreasing, CO2 emissions reduction in the Japanese market is moderate because the number of tyres sold in 2020 is 11.22 million less than in 2016 partly due to the impact of COVID-19.
