Abstract
The study conducted by a study group on the prediction of car fuel savings realized through tribology development organized by the Japan Society of Tribologists showed that the fuel loss caused by tires was 7.5% for constant velocity running at 60 km/h. Furthermore, the Japan Automobile Tyre Manufacturers Association estimates that the contribution rate of the reduction in tire rolling resistance to fuel savings is between 20 to 25% in the case of constant velocity running, and these figures cannot be explained if we consider the fuel loss of tires alone. The study group adopted a threefold improvement in fuel economy, as it reduces both the exhaust and cooling losses in the same ratio. In addition, the study group proposed a novel retroactive effect, which states that reduction of downstream elements’ losses decreases the upstream elements’ losses. The contribution rates of the individual elements to the fuel consumption can be calculated by taking the threefold improvement and the retroactive effect into consideration.
