Bike frame stiffness: Why it matters and all you need to know

Re:Bike frame stiffness: Why it matters and all you need to ... by fluoridation on Wednesday December 21, 2022 @07:43PM (#34088306)

No, it's not wrong. Given the same cross-section and initial speed, a heavier object moving through a fluid over a certain time will decelerate less than a lighter object, and so will require less energy to bring it up to the speed it had before decelerating, because the difference in speed will be less. For the same reason, you would not ride while dragging an open umbrella behind yourself, but you'd have no problem putting a metal cube of the same mass on your stem. It's the ratio of cross-section and mass.

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Re:Bike frame stiffness: Why it matters and all you need to ... by roelschroeven on Thursday December 22, 2022 @07:20AM (#34092610)

> a heavier object moving through a fluid over a certain time will decelerate less than a lighter object

True

> and so will require less energy to bring it up to the speed it had before decelerating, because the difference in speed will be less

False

The higher inertia of the heavier object resisted the deceleration, and that same higher inertia will resist acceleration too in exactly the same way. You've gained nothing at all.

> For the same reason, you would not ride while dragging an open umbrella behind yourself, but you'd have no problem putting a metal cube of the same mass on your stem. It's the ratio of cross-section and mass.

Now you're talking about aerodynamics which is a whole different matter. For aerodynamics, cross-section is of course a major factor (not the ratio of cross-section and mass!). That's pretty obvious, but has nothing to do with a discussion about mass.

(Ratio of cross-section and mass is relevant for things in free fall, because there gravity is the relevant force. Completely different from a vehicle on a flat road.)

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