Originally Posted by
makeinu
Myth: Since small wheels have less inertia they accelerate faster.
Fact: No. Since a properly designed geartrain will make small wheels spin faster (so you don't have to pedal more) they will not have less inertia and they will not accelerate any faster unless they are lighter. Physically speaking this is really the same myth as the "pedal more" myth, but, paradoxically, proponents of small wheels usually cite the former while opponents usually cite the latter.
Your words "unless they are lighter" are critical on this issue because small wheels are lighter than comparable large wheels.
Assuming that we are talking about comparable wheels with similar width and style of tyres, similar rim cross sections similar hubs and similar spoke types:
Small wheels have both less linear inertia and less effective rotational inertia.
Linear inertia
Small wheels have less linear inertia because they are lighter. They are lighter because the smaller circumference means that the tyres tubes and rims weigh less and the smaller radius means that the spokes weigh less.
Effect of Rotational Inertia
Your argument correctly identifies that the rpm of a small wheel is correspondingly greater than a large wheel. At any given road speed, the tangential velocity is independent of the size of the wheel.
Since its the mass at the rim that matters for rotational inertia and it has to be accelerated to the same velocity regardless of wheel diameter there would be no significant difference in effective rotational inertia if the mass at the rim were the same.
As the mass at the rim (rim, tube and tire) is actually much less, then so is the effect of rotational inertia on your ability to accelerate the bike.
David