Originally Posted by
Ogsarg
As I understand it, an object will sink when the mass of the object exceeds the mass of the liquid that it will displace. It has no direct correlation to the amount of air other than an object filled with air weighs less than an object filled with most other substances. This makes for a tricky calculation when considering a bicycle.
If you separate the frame from the wheels/tires, it may help somewhat. Since steel weighs roughly 10 times as much as water, a steel frame that did not hold air would sink for sure. The wheels and tires on the other hand would obviously float since the volume of the wheel (the amount of liquid it needs to displace) is made up largely of air, which weighs a tiny fraction of water
Of course it's displacement that matters. But balloon tyres and disc wheels "hold a lot of air" is another way of saying that "it displaces a lot water with not much weight since it's a hollow shell and water cannot fill it."
Carbon is lightweight, but only when made into structures. Solid carbon sinks really fast on its own.
So it comes down to weather the buoyancy of the wheels is enough to overcome the lack of buoyancy in the frame. I guess if you had all the details on every part, you could figure this out, but way too much work.
A frame as in the video is also hollow. Some old steel bike, while hollow, isn't really displacing enough water (i.e. have enough volume that can't be flooded) to float.
At the end of the day, if the Ferry starts to sink, I suspect the least of your worries will be whether your bike floats.
I agree. Who gives a flying flock about the safety of one's bike in such a situation.