The 26 Sep 2011 natural gas vehicle road trip across Oregon (a favorite region due to the lack of public fueling) using a 2004 Honda Civic GX showed a ten percent improvement in fuel economy using the Bridgestone B381 tire. This is in comparison to the same trip in 2009 using the Goodyear Integrity tire (which is standard on Prius hybrids.)
Distance of the run and the pressure drop in the fuel tank measured were:
215 miles 2160psi Chico - Medford (Siskiyou summit 4310)
216 1900 Medford - Salem (
190 2000 Salem - Seattle
The 2009 trip had 200 psi less in the fuel tank when reaching Salem from Medford. An oil filled tank pressure gage installed by AFTech Huntington Beach CA was used for test measurements. Cruise control was set at 60 mph for all runs. RPM was held to below 3000 when climbing mountain passes, sometimes bringing speed down to 40mph (just like the big rigs.) Tires on both trips were inflated to 41 psi to allow road heat to increase pressure to the 44 psi maximum. (1)
The Society of Automotive Engineers (SAE) has developed test practices to measure the Rolling resistance coefficient (RRC) of tires. The value of the RRC is the force divided by the wheel load. Using the tests (SAE J1269 and SAE J2452) most new passenger tires have reported RRCs ranging from 0.007 to 0.014. (1)
0.0097 Goodyear Integrity P185/70/R14
0.0062 Bridgestone B381 P185/70/R14
Trip was made possible due to CNG time-fill arrangements in the Oregon City area as well as using (public) fast fill stations in Chico, Medford, and Seatac.
Bill Stallman 510 479 5374
Low Rolling Resistance Tires:
For conventional passenger tires, an increase in inflation pressure from 24 to 29 pounds per square inch (psi) will reduce rolling resistance by 10 percent. For a tire inflated to pressures between 24 and 36 psi, each drop of 1 psi leads to a 1.4 percent increase in its rolling resistance...there is a long-standing rule of thumb that a 10 percent reduction in RRC will yield a 1 to 2 percent increase in vehicle fuel economy.