Originally Posted by
Fredo76
I believe my signature is a concise statement of the physics, and not an exaggeration.
For mass at the rim, it's a concise statement of the impact on inertia. However, the statement...
"
When you're trying to go faster, an ounce off the wheels is worth two off the frame."
...presents it as a holistic description of how mass affects performance, which is not the case. Even if we're only looking at the high-level kinematics, there's also gravity, which on many rides consumes a much larger total energy contribution than inertia.
More broadly, mass also affects how a bike dynamically feels, and this can depend heavily on the specific distribution. For example, mass at the saddle has a larger effect on how easily a bike throws side-to-side than mass at the bottom bracket. Or if we're looking at the steering effects of gyroscopic precession, mass on the front rim has an essentially infinitely-larger effect than mass on the bottle cage.
That being said, the impacts that
these things have on "
performance" are extremely difficult to quantify, and it's not necessarily the case that greater mass is always detrimental with respect to them.
Or, put another way...
If you know the correct coefficient for the simplifying assumption that the rotating weight is all at the radius, do tell.
...Unless caveats are added to make the matter more specific, it's a loaded question. You can't reduce the effect of placing additional mass on the rim versus the frame to a single generally-applicable number.