Tire sidewall height vs rolling resistance?

[CapriRacer]

Originally Posted by MeteorGray

Going back to this thread's title question: "Tire sidewall height vs rolling resistance?"

With a given wheel diameter for a car and all other things being equal, for less rolling resistance is it better to have more rubber in the tire's sidewall with a smaller metal hub/rim, or is it better to have less rubber in the tire's sidewall with a larger metal hub/rim?

Stated another way, for lower rolling resistance is it better to achieve a 26-inch-diameter wheel with a 16-inch metal hub/rim or an 18-inch metal hub/rim?

OK, you asked 2 different questions:

1) If the "wheel" diameter is fixed, what affect does the sidewall height have on RR? I'm going to answer this question where "wheel" means the same as "rim" - which is not what I think you meant. If I don't assume that, then this question is the same as #2).

2) If the overall diameter of the tire is fixed, what affect does different rim diameters have?

For #1) - applying the bigger is better rule: More sidewall height = better RR.

For #2) - It's a bit more complicated, but more sidewall height = more load carrying capacity (which is another way of measuring "bigger"), so less rim diameter = better RR.