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. 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.
Read more about this topic: Low-rolling Resistance Tires
Famous quotes containing the words measuring, rolling, resistance and/or tires:
“We recognize caste in dogs because we rank ourselves by the familiar dog system, a ladderlike social arrangement wherein one individual outranks all others, the next outranks all but the first, and so on down the hierarchy. But the cat system is more like a wheel, with a high-ranking cat at the hub and the others arranged around the rim, all reluctantly acknowledging the superiority of the despot but not necessarily measuring themselves against one another.”
—Elizabeth Marshall Thomas. “Strong and Sensitive Cats,” Atlantic Monthly (July 1994)
“Lift every voice and sing till earth and heaven ring,
ring with the harmonies of liberty.
Let our rejoicing rise high as the listening skies;
Let it resound loud as the rolling sea.”
—James Weldon Johnson (1871–1938)
“The resistance we make to our passions is due to their weakness, not our strength.”
—François, Duc De La Rochefoucauld (1613–1680)
“One never tires of what is well written, style is life! It is the very blood of thought!”
—Gustave Flaubert (1821–1880)