Originally Posted by ExMachina
Perhaps I misread you initial post since I thought I was talking about wheels too
Anyway, I agree, that a heavier bike/wheel combo will take more energy to get up a hill.
However, after having had my morning coffee, I am more certain than ever that neither the weight nor the distribution of weight in a wheel set (provided that the overall weight of the bike stays the same) will by itself affect the total energy expended by a rider (ie, an avg speed over a set distance). Wheel weight and wheel weight distribution will only affect the
rate of acceleration/decelleration--the work being preformed by the rider will stay the same.
Yes, weight will affect the rate of accelleration, but also the peak rate of velocity and energy use. Assuming you want to maintain a constant speed.
For practical physics I like to use extreme examples:
Think rolling a tennis ball and a 100 lb lead ball up a 15% grade. You want to keep them both rolling at 1 MPH. Which will require more energy? Obviously the lead ball. Now which takes more energy to keep moving on a flat surface? Again, the tennis ball, but the difference in energy required to keep both objects in motion narrows considerably.
Next, think about rolling two wheels, both six feet in diameter. Both weight 100 pounds. One has
a 99 pound lead weight as the axle.
The other has 99 pounds of lead strapped wire wrapped around the outside of the hoop. Which will require more energy to keep moving at a constant rate of speed up a 20 degree hill?
When you're riding you are constantly accellerating and decelerating, sometimes in minute increments. Going uphill these these accellerations more pronounced, requiring more energy to keep all things moving.
Regardless of gradient, it takes more energy to keep a heavier object in motion.
My comments also assumed that we were talking wheel weight on the same bike, not different bikes of equal weight.