Quote:
Originally Posted by Vekke
I will try to do some kind of coastdown test with two suberb tires:
145/80R14 Bridgestone B381 Ecopias. Original Audi 3L tire size.
175/70R14 Nokian Hakkapeliitta R. One of the best LRR tire available at the moment.
So the test will be a coastdown test from 140 km/h to 0. I will measure the distance diffence but also the times which it will take to 140-65 (aero) and 65-0 (Rolling resistance). I will appreciate more aero but those are also 3% taller so I have to test them also while driving to see which is actually better... Rolling resistance wise Nokians should be best with clear margin  . Pressures in both tire sets always 3.5 bar. |
Rolling resistance always plays a role, however its effects are masked by the aerodynamic road load forces above a certain speed. Therefore the force that it requires to overcome the sum total of the wind resistance, grade resistance and road load force combine in their effects upon the coast down distance from any speed. As a rough calibration it may be possible to roughly estimate the forces required through the use of the road load calculations, however they will only be as accurate as the input data, which will require knowing the rolling resistance of the tire (a standard tire might have a crr of 0.010 and a lrr tire a 0.008), the aerodynamic coefficent of drag, the target speed or speed range, the frontal area and the mass of the vehicle.