Originally Posted by Carbonfiberboy

Conventional wisdom has been that a pound on the wheels = 2 pounds on the frame. I've often wondered about that, because physics suggests this is not the case.

Wheels are different from a frame in that their energy is composed of both forward momentum and angular momentum. Thus a heavier wheelset will cause a bike to accelerate more slowly than the same additional weight on the frame.

Many people climb standing or with a strong downstroke instead of pedaling circles. In these cases, the bike is accelerated with every pedal stroke. Physics says that you get the energy spent performing this acceleration back during the deceleration phase. However, everyone knows that a lighter bike with lighter wheels feels easier on a climb, more so than losing the same weight off one's body. Hence the desire for lighter equipment.

My guess is that the higher momentary energy output required of the leg muscles to accelerate the heavier wheels is not returned completely during deceleration. IOW, the peaks and valleys of muscular output are more pronounced. That makes one tired.

New tandem captains who are experienced single riders can be blown away by this. One can produce the same power or ride at the same HR as normal, yet be more exhausted in one hour on a tandem than one was by 2 hours at the same apparent effort on one's single. I think it's because the heavier bike resists momentary accelerations and thus places higher momentary loads on the leg muscles. A new captain eventually adapts to this and learns to pedal and apply power more smoothly, but the adaptation can take a long time.