In a message dated 21/04/01 13:50:57 GMT Daylight Time, KCTOMMY@email.msn.com writes:
> Regarding the lighter wheel set being easier to accelerate, I once had an
> engineering professor explain to me that because every pedal stroke
> accelerates and decelerates, you continually reap the benefits of lighter
> wheels. To my "dumb look", he explained that as your foot goes over the top
> and changes direction from up to down, it is in effect coasting and slowing
> down, and speeds up and your leg drives down through the power stroke. It's
> not noticeable on the flats, he said, but compare light wheels to heavy
> wheels on a steep climb when you're pedaling a slow cadence. I certainly
> noticed a much livelier feel when I climbed our local "bad hill" on my first
> set of tubulars. Likewise when I swap between my "touring wheels" and the
> "racy wheels" on the Marinnoni. Much more so than just throwing half the
> tools out of the saddle bag for equivalent weight savings
I hope that this engineering professor got a new job. Weight at the wheel hub is effectively the same as weight anywhere else (I know that I should say mass, but weight is more comprehensible). Weight at the rim/tire requires more force to accelerate than non-rotating weight; by the same token, the deceleration is slower when the driving force is removed. Travelling at constant speed on the level, the heavier wheel requires no more force to keep it going (assuming equal rolling resistance). Similarly, an overall heavier bike requires more force to accelerate, but no more force to keep it going at a steady speed on the level.