Originally Posted by
PeteHski
That Swiss study was specifically comparing two different models of mountain bike (not just wheel size independently) on a mountain bike off-road course. So there are numerous reasons why their newer 29” mtb might have been quicker over that technical course. Since then 29” MTBs have dominated XC racing, but not DH mtb, where smaller wheel sizes are still popular. But none of this is relevant to your Roadlite on pavement. All the studies of wheel size on pavement show no significant speed difference between 700c and 650b wheels.
Descending speed on the road is all about aerodynamics, rolling resistance and mass. It is not about wheel diameter. So rider weight, position on the bike and tire choices are what will differentiate their speed.
Incidentally did you know that smaller wheels on track bikes were banned decades ago because of their aerodynamic advantages? It’s before my time, but there was one team who had track bikes with very small wheels, which looked very odd but it was very fast because of the lower aero drag.
I did not know about the small-wheel ban on track bikes. The Reynolds AR41 650b wheels on my Roadlite might be considerably more aerodynamic than the DT Swiss P1800 700c wheels on my Ultimate. Both bikes have Continental GP 5000 28mm tires, and are both around the same weight. Maybe the Roadlite will ride even faster... we'll see soon.