Quote:
Originally Posted by mort
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
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I disagree.
As a winter bicyclist I'm keenly aware of a
massive increase in r.r.. Bearing losses for motored vehicles are considered by SAE to be small enough to ignore in performance calcs (and their bearings have draggy lip seals); indeed when I spin a bike wheel in the cold it seems to spin nearly as well as ever (WARNING! Completely subjective!). I blame the tires themselves.
You say steel belts are the biggest
contributor to r.r. when actually they are the biggest thing that
reduces r.r.; steel springs back efficiently thus returning nearly all the energy it took to deform it vs rubber which due to hysteresis doesn't return as much when "undeforming"; thus the rubber is the culprit in absorbing energy when rolling.
I think the amount of flexion isn't changed much by temps (???) because the load on the tire is constant.
Oh, to have low r.r. steel belted bicycle and motorcycle tires!!! I think the super low r.r. tires used on solar racers are steel belted...
We know that tubeless tires have lower r.r. than tubed; more rubber = more r.r.