Quote:
Originally Posted by mort
Hi Diesel_Dave,
See here.
The EPA temperature adjustment for tire rolling resistance:
So tire RR decreases about 22% at 0 compared to 68 degrees F. Which is going the wrong direction. The largest contributor to RR in modern tires is the stiffness in the steel belts, and that is almost unchanged for the range of temps that a tire sees. The change in the flexibility of the rubber at low temps is likely unimportant. In fact, as the rubber gets stiffer it flexes less so it should roll easier. I'd look at the viscosity of bearing and gear greases as the main culprit.
-mort |
So that means they assume it's linear and the RR increases 1% for every 3 deg F you drop from 68 deg F.
That seems ballpark reasonable. Several flolks around here have a rule of thumb for FE vs. temp which is ~1% FE change per 2 deg F change. I think if you calculate air density changes you can ascribe ~1/2 that to aero.
This paper from '77 does talk about the changes to the rubber hysteresis, however, they don't give much data (see page 8):
http://www.edccorp.com/library/TechRefPdfs/EDC-1038.pdf
I also found a reference to an SAE paper from '80, but haven't found the full text yet:
http://papers.sae.org/800090/