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Low rolling resistance tires minimize wasted energy as a tire rolls, thereby decreasing required rolling effort — and in the case of automotive applications, improving vehicle fuel efficiency. Approximately 5–15% of the fuel consumed by a typical car may be used to overcome rolling resistance.〔(Low Rolling Resistance Tires ) (Website). Energy Efficiency and Renewable Energy, U.S. Department of Energy. Retrieved on 2007-08-11.〕 A 2003 California Energy Commission (CEC) preliminary study estimated that adoption of low-rolling resistance tires could save 1.5–4.5% of all gasoline consumption, but that current data were also insufficient to compare safety and other characteristics.〔(California State Fuel-Efficient Tire Report: Volume I ) California Energy Commission, July 2003. Retrieved on 2007-08-11.〕 A database of much more complete data will be released by the CEC pending completion of an ongoing study.〔(Tire and Fuel Efficiency ) California Energy Commission, June 2006. Retrieved on 2007-08-11.〕 A U.S National Highway Traffic Safety Administration (NHTSA) study in 2009, if 2% of the replacement tyres would reduce their rolling resistance by 5%, there would be 7.9 million gallons fuel and 76,000 metric tons of CO2 saved annually. == Measuring rolling resistance in tires == Rolling resistance can be expressed with the rolling resistance coefficient (RRC), which is the value of the rolling resistance force divided by the wheel load. A lower coefficient means the tires will use less energy to travel a certain distance. The coefficient is mostly considered as independent of speed, but for precise calculations it is tabled at several speeds or an additional speed-dependent part is used. The Society of Automotive Engineers (SAE) has developed test practices to measure the RRC of tires. These tests (SAE J1269 and SAE J2452) are usually performed on new tires. When measured by using these standard test practices, most new passenger tires have reported RRCs ranging from 0.007 to 0.014.〔("Tires and Passenger Vehicle Fuel Economy: Informing Consumers, Improving Performance -- Special Report 286." ), National Academy of Sciences, Transportation Research Board, 2006. Retrieved on 2007-08-11〕 In the case of bicycle tires, values of 0.0025 to 0.005 are achieved.〔http://www.biketechreview.com/tires/AFM_tire_crr.htm〕 These coefficients are measured on rollers, with power meters on road surfaces, or with coast-down tests. In the latter two cases, the effect of air resistance must be subtracted or the tests performed at very low speeds. In 2009 The CEC used a rating called Rolling Resistance Force RRF. RRF and RRC, rolling resistance coefficient are very similar. Difference is taking the RRF and dividing it by the load(weight) to get RRC. So a Michelin Harmony tire rated at 9.45 RRF at 1000 pounds load would be .0095 RRC.〔(California Energy Commission )〕〔(77 tires RRF )〕 In Canada, Transport Canada tests will be conducted on a number of different tires mounted on 15 and 16-inch rims – the most common tire sizes in Canada – to determine how rolling resistance is influenced by vehicle size, tire width and profile. Results will be used to inform Canadians about the types of low rolling resistance tires available in Canada, and whether they can help reduce fuel consumption and pollutants from passenger vehicles.〔(Transport Canada LRR Study )〕 SAE J2452 is a standard defined by the Society of Automotive Engineers to define the rolling resistance of tires. The rolling resistance coefficient (RRC) indicates the amount of force required to overcome the hysteresis of the material as the tire rolls. Tire pressure, vehicle weight and velocity all play a role in how much force is lost to rolling resistance. The basic model equation for SAE J2452 is: Rolling Resistance ( N / Lbs) = Pα x Zβ x (a + bxV + cxVxV) where: P is the tire inflation pressure ( kPa / psi) Z is the applied load for vehicle weight ( N /Lbs) V is the vehicle speed ( km/h / mph) alpha, beta, a, b, c are the coefficients for the model. The units of the coefficients are matched to the units used in the model, i.e. ( metric / Imperial) This model is newer than SAE J1269 and provides more accuracy over a range of different vehicle loads (weight), tire pressures and vehicle speeds. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Low rolling resistance tire」の詳細全文を読む スポンサード リンク
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