Quote:
Originally Posted by Big Dave
Check out http://greenseal.org/resources/repor...resistance.pdf
Especially the graph on page 4 and the tabulation on page 5.
The low rolling resistance 14 inch tire was the Bridgestone B381 185-70R14 (OD = 24.2 inches) Rolling resistance coefficient = 0.0062
The low rolling resistance 15 inch tire was the Mihcelin Arctic Alpine 235-75R15 (OD = 28.9 inches) Rolling resistance coefficient = 0.0081
The low rolling resistance 16 inch car tire was the Continental Conti Touring 205-55R16 (OD = 24.9 inches) Rolling resistance coefficient = 0.0083
The low rolling resistance 16 inch truck tire was the BF Goodrich Long trail T/A 245-75R16 (OD = 30.5 inches) Rolling resistance coefficient = 0.0092
The little Bridgestone 14 incher had a rolling resistance coefficient that is 33% lower than the BF Goodrich. The 14 incher had an OD that was 21% smaller than the BFG.
The 15 inch Michelin filled the middle range but the Conti was anomalous.
Yeah the data is five years old but you use what you’ve got. Rolling resistance coefficients are not something easily found.
I do agree that "bigger diameter = more rolling resistance" seems counter-intuitive but tires are generally considered the “voodoo” of vehicle dynamics. |
I can't read pdf from here but it's plain to see that your examples are not comparable tires that are merely different sizes. As sidewall and tread thickness goes up, r.r. goes up- these tires are plainly meant for different load ranges. Also the treads are likely to be quite different in design and depth. You are claiming that because a big heavy truck tire has higer r.r. than a light little passenger car tire, larger diameter leads to higher r.r.. You know the flaws with that and I shouldn't have had to point them out.