Groucho Marx's pithy review of a collection of pieces by the brilliant New Yorker humorist S. J. Perelman: "I laughed until I stopped."

In the absence of the biological component, bikes remain upright until they fall over.

Of course, they remain upright as long as they do thanks to their being counter-steered by an unseen agent of the spirit world.

Well, it's complicated enough that full definitions eluded the best engineers and scientists until that 2011 study from Delft and Cornell. Previous studies using physical tests had proven that positive trail/caster improves stability, and a bike is nearly unridable with negative trail, but still felt that some positive trail was essential. Other studies had also built bikes with counterrotating wheels to cancel gyroscopic effects, and proved that gyro helped, but was not essential. But before 2011, no one had conclusively proven the effects of mass distribution. There may have been some general statements, and I recall a sales poster from Blackburn decades ago, illustrating best locations for mass distribution on bike racks. But the 2011 study not only demonstrated via physical tests, but created mathematical methods, speeded greatly by computers, that indicated stability based on mass distribution, and exactly where stability began to vanish based on that, and verified in actual tests. That was a big advance.

Two wheel vehicle dynamics have always been more difficult than four wheel (due to the degree of wheel tilt, i.e., camber change, on two wheel vehicles), and I'm sure that analysis happened on motorcycle design before unpowered bicycles, as it's more critical; Instability issues at high speed can devolve into "tank-slapper" uncontrollability, and many, if not all, high speed motorcycles require a steering damper to improve stability. On bicycles, front "shimmy" on high speed descents was a thing, and I think has disappeared with frames that are stiffer in torsion and forks stiffer laterally; I'd bet money that now, all high-speed capable road bikes are modeled and/or tested for shimmy before going into production. The analysis might be performed on homegrown computer applications, or perhaps using ADAMS (currently MSC ADAMS) dynamic software application.

I purchased my copy of this about 65years ago. It has a very thorough explanation of two wheel steering dynamics and I'm fairly certain that Mr.Irving was far from the first to explore that. BTW, he designed the Vincent/HRD motorcycle among other things

https://cimg4.ibsrv.net/gimg/bikefor...f171c3408.jpeg

A circus bear knows better than many BF'ers how a bicycle works.

This is not surprising. ;-)

55murray was right. It's biology, not physics. Bears can learn counter-steering!

There's no doubt that counter-steering works to control a bicycle. But it's not required to keep a bicycle from falling over.

Generally, when some with no science background claims "science doesn't understand xyz", it just means the person making the claim doesn't understand xyz.

I'll just see myself out.
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I still prefer pith over fiss (phys). Less boring. I found my physics class interesting and excruciating.

Bicycles don't ride themselves. They just fall over without a rider.

Yes, they do.

Really!

Right. As I understand it, deliberate/intentional counter-steering is necessary with (heavy) motorcycles but is optional with bicycles.

Bicycles fall over eventually, but only when they run out of forward motion.

Bicycles. Are. Self-stabilizing.

Not quite
But
Newton's First Law will assist ...... ........ Until ...

For extra credit: would a wheel alone roll longer than the bike? Would a ski bike do this?

Good questions.

A wheel rolling alone is pretty stable, but once it starts to tilt over, it won't correct, instead spiraling into smaller and smaller circles until falling over.

A ski bike... there are numerous issues. There's no gyro stability. The front ski length will inhibit self-steering, regardless of mass distribution on the ski-bike. Maybe if the front steering axis were well ahead of the front ski, so castering effects, as the bike falls over, perhaps the castering will make it steer into the fall. Very difficult to predict.

That tandem fairly GLOWS! :love:

I met Phil Irving at a Vincent Owners Club meeting in Chicago about 50 years ago. (Sadly, I was not a Vincent owner.)

This book occasionally comes in quite handy. :foo:

Yowsa ! That would have been fantastic ! I did get to ride on a Black Shadow once but that was as close as I ever got.

I was in awe. So much so that, to my lasting embarrassment, I referred to his wife as "Mrs. Vincent". :o
Both of them took it in good humor, and were very pleasant. Mr. Irving was a bit self-deprecating about his design of the Vincent V-win engine... he said he just overlaid a tracing of the single-cylinder engine, rotated it a certain number of degrees, and noticed that there was a place for a second cylinder.
In 1981 I went to a national Vincent Owners Club meeting at Nelson Ledges Road Course where I got to take my BMW R100S out on the track. I got up to 100+ MPH on the straights, the whole time being passed by vintage British bikes like I was standing still. There was a Concours d’Elegance exhibit where I got to sit on the bike that Rollie Free rode at the Bonneville Salt Flats in 1948. It was a memorable event.

:o. Lack of use - unfortunately.
Physically, tho' = it served a purpose with 2 kid stokers.

https://cimg8.ibsrv.net/gimg/bikefor...7a971c822f.jpg

It would be more accurate to say that the person creating this video doesn't understand how a bicycle works. Bicycling Science, 4th Edition, Wilson, was published by MIT press in 2020, and the 1st edition was published in 1974. A lot of knowledge out there for those who wish to seek it out, study it, and understand it. Bicycling is like church: many attend but few understand.

I've quoted David Gordon Wilson a few times on these Forums. Each and every time there is a huge chorus of proclamations this author does not know WTF he is talking about. Being an emeritus professor at MIT and Cambridge does not count. Being the world record holder for miles on an epicyclic hub does not count. Being the founder of the International Human Powered vehicle Association does not count. Having an internet opinion does count.

As I have pointed out several times, Mercans are born knowing better.

I'd say it starts with a nut loose behind the handlebars.

And there you have it. As Stephen Colbert famously said: Truthiness. My gut feelings trump your science every day! And let's not confine that to just the internet.