Originally Posted by
thdave
So??? You're cranking for a longer time and the wheel's heavier. I think it has been proven that the efficiency difference between the wheels is next to nothing.
If the crank arms are the same size, why would you be cranking for a longer time (assuming you're feet are moving at the same speed) ?
The larger wheel will be heavier of course, -all else being equal, but you've got to spin the smaller wheel faster to cover the same distance so now the aerodynamics of spokes and what not come more into play. I would guess too that there's more friction issues at the hub on the smaller wheel, since it has to spin faster, but I think the larger wheel would actually have more friction with the road (smaller wheel would curve away more sharply). On the other hand, the spokes on the smaller wheel would be shorter and that might compensate for the additional drag of having to move faster... ;-)
Interesting stuff but there's probably not that much difference in practical matters since the wheels aren't radically different in size and 26" tires tend to have taller sidewalls anyway so the effective difference is probably even smaller.