Low rolling resistance tire
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. 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. A database of much more complete data will be released by the CEC pending completion of an ongoing study.
A U.S National Highway Traffic Safety Administration (NHTSA) study in 2009, if 2% of the replacement tires would reduce their rolling resistance by 5%, there would be 7.9 million gallons fuel and 76,000 metric tons of CO2 saved annually.
Rolling resistance can be expressed by the rolling resistance coefficient (RRC or Crr), 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. In the case of bicycle tires, values of 0.0025 to 0.005 are achieved. 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.
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. SAE J2452 is a standard defined by the Society of Automotive Engineers to define the rolling resistance of tires.
...
Wikipedia