Editing Rolling resistance (section)

== Measurement ==
There are at least two popular models for calculating rolling resistance.

#"Rolling resistance coefficient (RRC). The value of the rolling resistance force divided by the wheel load. 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{{Citation needed|date=June 2008}} 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."<ref name = "NAS286" /> In the case of bicycle tires, values of 0.0025 to 0.005 are achieved.<ref>{{Cite web|url=http://www.biketechreview.com/tires/AFM_tire_crr.htm|title=Roller Data|last=Willett|first=Kraig|website=www.biketechreview.com|language=en-gb|access-date=2017-08-05}}</ref> These coefficients are measured on rollers, with power meters on road surfaces, or with [[coast-down test]]s. In the latter two cases, the effect of air resistance must be subtracted or the tests performed at very low speeds.
#The coefficient of rolling resistance ''b'', which has the dimension of [[length]], is approximately (due to the [[small-angle approximation]] of <math>\cos(\theta) = 1</math>) equal to the value of the rolling resistance force times the [[radius]] of the wheel divided by the wheel load.<ref name = "Hibbeler" />
# [[ISO 18164:2005]] is used to test rolling resistance in Europe.

The results of these tests can be hard for the general public to obtain as manufacturers prefer to publicize "comfort" and "performance".