Originally Posted by
cshell
and yet, I can see this as correct at the same time.
On a grand scale, consider this.
Let's say it takes the same amount of time for Mercury to make one full revolution around the sun as it does Neptune. (I know this is NOT true, but for the example...)
(Mercury is closest to the sun, Neptune is farthest).
They both take X amount time to get around one full revolution.....
Which planet was moving faster? Take a 1/4 of the distance of each planet, and measure that speed. You'd think if Neptune had to travel SOOO much more distance in the same amount of time, wouldnt' it be traveling faster?
But at the same time, they end at the same points, at the same time, yet Neptune travel milliions of miles farther.....
This is a completely irrelevant analogy. The distance traveled on a bike is entirely dependent on the distance traveled by a given point which is the distance of the contact point from the center of the wheel.
The magnet is simply a tool to measure revolutions, and then the distance (and speed) are calculated as a function of these revolutions and the radius entered into the computer.
In other words, it does not matter what point you use to measure the revolutions, because we don't care how far that point travels at all. We only care about how quickly that point makes revolutions, because that is the only input that matters for the computer. It should be obvious that the distance of the point from the center has no impact on number of revolutions.
Edit: You'll notice, however, that the radius is a key variable in the calculations that the computer makes. Having fuller or flatter tires WILL have an impact on distance recorded. Accurately measuring from the center to the contact point (while loaded) will yield the most accurate computer measurements.