Mick F wrote: You can see that the cheaper wheels went further! (albeit only half a wheel revolution further)
Why is this?
I started reading this thread with a gut feeling that different wind resistance, as a result of different riding postures, could be as significant as different rolling resistance.
I then went to CJ's calculator. Mick, you suggested you may have topped at 5 mph. At that speed, wind resistance, with a drag coefficient of 1 and a frontal area of 0.5 square meters, would be 3.6 watts. Rolling resistance, however, with a coefficient of 0.006 and a mass of 100 kg, would be 13.7 watts.
So I concluded that wind resistance was indeed, as you had claimed and contrary to my instinct, likely to be small compared to rolling resistance.
But your latest measurement has barely 1 - 2% difference. That is small enough I could believe it could be attributed to differing drag coefficients. But equally it is so small it could be attributed to a wet road or warmed-up hubs as you suggest, or to the tyres being pumped to a marginally different pressure, or to almost anything else!