If your bicycle is on the deck of a transit ferry and falls into the water, take one last look because that will be the last time you ever see it. Doesn't matter it it floats or sinks, wave goodbye.

2 inch tires look to get about 2.5-3 liters for the set so not looking great here neglecting buoyancy of the rest of the bike.

Now if you get a fat bike and something like 5 inch tires your are probably at 12-15 kg so looks maybe doable.

I didn't try to math too much but should be close enough...

I can assure you based on practical experience that a 90s steel hardtail is going to sink like a rock.

I’ve walked my mtb through some pretty deep waters on occasion. Wheels fully submerged. They stayed resolutely in contact with the bottom. 26x2”
My brother’s Fat Bike didn’t even get the hubs wet.

Kaching, with a resounding CHING!
"You have reached SimplyDevineInsuranceCo claims dept, how may I help you today?"

Fuji Tahoe or Chevy Tahoe?

To me, the only relevant question is, Is it still rideable or worth anything after being pulled from the water, whether it was "on" it or "in" it or "under" it.
That said, I read somewhere that the airplane that Capt. Sulberger landed ON (not in) the Hudson River without loss of life after it lost power was salvageable.

don't worry , didn't happen. This was just covid pandemic boredness mulling.

Planes are very, very expensive, rescuing/reusing parts of it was most likely worth it. A bike would propably mean you could reuse some parts too, but propably not the hubs, rims, etc. The saddle, seatpost, handlebars, and so on would certainly be salvageable. But the rest on a steel bike? I don't think so. Imagine the frame on the inside after a couple of months down the line. Ugh.

You could use a plastic can tied to the bike.

I could be wrong but I think they were actually able to fly it. There was very little damage, the greatest being to both engines from the geese that had met their demise in them. The hull/fuselage wasn't breached and the wings stayed on. Large aircraft rarely survive ditching attempts. In every previous attempt to land a civil airliner on water, either the tail breaks off or one wingtip hits rough water first and the plane does a cartwheel, with loss of all souls as the plane disintegrates or the fuel ignites.. (Unlike the Air Canada pilot who landed a 767 with empty tanks on an abandoned airstrip, Sulberger had fuel on board and no time to dump it. The Right Stuff I guess.)

But back to the topic, maybe the inflated evacuation slides contributed to buoyancy. .

That's impressive! I didn't know that.

Thanks for the feedback and pondering. This is very much just a thought exercise to pass some time. That's how it all started, as I was contemplating various things while being ferried (I refuse to simply stare at my phone, as 99% of the other passengers do), and then at a certain point I said to myself, 'I should see what the people on the forum think would happen.'

I don't think I'll ever have to find out the hard way, and certainly hope not, but as people have said my bike would be the least of my concerns.

On my one "fancy" bike, yes, I do. But I very rarely ride that one to work.

That's a good point, as I hadn't really thought about duration..

It's looking like tires size/volume will play a big part. There are also different levels of buoyancy (in my mind, anyway) as some object are will barely stay at the surface while others are actually hard to push down. I was surprised to see how the fat bike in that video fared, and the same with the carbon bike.

Also, having spent a lot of my childhood swimming in a river with various flotation devices and lifelines around for safety, it's sometimes surprising how much buoyancy objects have. Anyone familiar with those square, foam seat cushions knows that one of them will pretty easily keep you afloat, despite not being that large. Likewise, I've been able to keep myself afloat with just a half inflated volleyball.

I know my Pugsley will float ... Not sure if it'd support me and itself.

In Amsterdam (I believe) people toss a ton of bikes into the water...so much so that they have to dredge them out on a regular basis (saw that documentary on Prime Video). I've never seen a floating bike. I believe there are Fat Bikes that float, but those are with really wide tires.

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

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.

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.

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.

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.

I agree. Who gives a flying flock about the safety of one's bike in such a situation.

This.

If we assume that the shape of a tire/rim/tube is a toroid (fancy name for donut), the volume is 2 X Pi^2 X R X r^2, where R is the radius of the wheel and r is the radius of the tube (half the width). For a 700x50mm wheel, the volume of air is 3.8 liters. A liter of water weighs about 2.2 pounds, so the bike would need to weigh less than 17 pounds to float. Bye bye, bike.

There probably aren't many 700 X 50 wheeled bikes that weigh less than 17 pounds, so you need to be solidly in fat bike territory to have a bike that reliably floats. a 26" x 2.4" tire would float about 11 pounds.

A 27.5" x 3", the tube would displace 8 liters, or 18 pounds. Two tires means 36 pounds of bike. Now we are getting somewhere A fatbike tire (26"x4") would displace about 14 liters, or 62 pounds of bike and gear. Getting closer. 26"x5" would displace 22 liters, or 96 pounds of bike and whatever or whoever is clinging to it.

No other tube is sealed well enough that it will not eventually sink. After the tires, bar tape and empty water bottles are your only salvation.

I was concerned about this as well, so sealed up my bike’s frame and filled it with helium.

As a bonus, the lighter bike is faster and climbs more easily.

This only works with carbon though. Steel may be real, but you can’t float it with any of the noble gasses.

You should also be realistic about how much time, effort, and money you put into this given your time on the water. I only did it cause I’m on a ferry a couple times a year at least.

To be as pedantic as before in this thread: You didn't fill it up with helium, you displaced the air with helium.

I, personally had a long think about it, and just bought* two packrafts. They weigh a bit (but not much), but I don't have to float around waiting for rescue. Now, where did I put my Torqeedo motor.


*No, obviously not for real.

The Wright brothers first accepted as successful powered flight was only 12 seconds.

How long does this have to float to say it floats?

Personally I'd think long enough to not have to go diving for it would be good enough. So 10 seconds maybe?

To save the bike when the ferry sinks, I'd say "much longer than 10 seconds".

The human body is right near neutral buoyancy. I'd rather have something that has 5 pounds of buoyancy than 5 pounds of sinkable weight.

I don't think the idea was that the ferry sunk. More that the bike fell off.

When I had my sailboat, it didn't take very long to grab a pole to fish out hats, buckets or other stuff that all my lily-livered scabby sea bass crew let fall off. If it fell off near the bow, I could nab it as it came past the aft cockpit without having to stop or worse, come about. <grin>

Don't know why I care about buoyancy at all. If I'm diving, as in SCUBA diving, I'll either have a BC vest on me that will more than overcome the bike weight or I'll take a line with me.

LOL, he meant falling over board? In that case, it doesn't matter if it floats. He should just tie a long string to it and to the ferry at the other end, that way it ought to be pretty easy to retreive regardless of it floating or not. Or lock it to something so it doesn't fall overboard by "accident".