Originally Posted by
terrymorse
And that rotating mass difference only matters when accelerating and decelerating. Heavier wheels accelerate AND decelerate more slowly. Total time over a course at a constant power will be identical, whether the weight is in the wheels, on the frame, or in the belly. Momentum is momentum, mass is mass, energy is conserved. Physics 101.
All these "I feel the difference" comments are irrelevant.
But there are a lot of different forces at work. Even though that air resistance plays a huge role in the fuel efficiency of a car, manufacturers also do what they can to reduce weight. They wouldn't do that if it didn't matter.