# My idea for how a bicycle balances **URL:** \ **Category:** In My Humble Opinion\ **Created:** [September 21, 2011, 1:24pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060 "2011-09-21T13:24:56Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [September 21, 2011, 1:24pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/1 "2011-09-21T13:24:56Z")
So I just discovered yesterday that the mechanism of how bikes manage to stay upright is still up for grabs. \ For decades the leading theory was that there was some gyroscopic effect responsible. But then it was shown mathematically that such an effect could not produce enough force to resist a rider’s weight. Then the leading theory was…positive castor? Something to do with weight being in front of the centre of the front wheel. Or something. Anyway that’s been refuted with the demonstration of a bicycle that has a very negative castor – or whatever the opposite is – that is nonetheless stable. So I was thinking – have we not just made this more complicated that it is? If I try to turn a corner on a bike, I lean into the corner to help me turn. And I feel a force pushing the bike upright because of the way my velocity is changing. Could it be that when riding in a straight line, any slight wobbles are immediately resisted as though I were trying to turn? (Possibly the rider might help this with steering because a bike pushed along with no rider is not very stable…) ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [September 21, 2011, 3:55pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/2 "2011-09-21T15:55:56Z")
I was going with inertia my whole life. Still going with inertia. Try to turn without managing the inertia (without leaning) and report back. Inertia. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [September 21, 2011, 4:09pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/3 "2011-09-21T16:09:01Z")
Yeah but your forward inertia doesn’t prevent you tipping left or right. How does it _balance_? ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [September 21, 2011, 4:43pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/4 "2011-09-21T16:43:13Z")
If you could devise a bike without wheels that might put your idea to the test. How about a bike with skates and a big push? ---
**Author:** ![BellRungBookShut-CandleSnuffed](https://avatars.discourse-cdn.com/v4/letter/b/bcef8e/32.png) [@BellRungBookShut-CandleSnuffed](https://boards.straightdope.com/u/BellRungBookShut-CandleSnuffed)\ **Post date:** [September 21, 2011, 4:44pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/5 "2011-09-21T16:44:41Z")
> [@Mijin](#): > > Yeah but your forward inertia doesn’t prevent you tipping left or right. > How does it _balance_? _It_ doesn’t balance, you do. There’s a reason people just learning to ride fall over. Once you get used to the tiny cues that your bike gives you that you’re leaning too far in one direction, you correct for them before the shift really becomes visible. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [September 21, 2011, 5:27pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/6 "2011-09-21T17:27:42Z")
> [@BellRungBookShut-CandleSnuffed](#): > > _It_ doesn’t balance, you do. There’s a reason people just learning to ride fall over. Of course the rider has an important role in balancing, but it’s much easier to balance on a bike the quicker it moves (within reason). It seems to require less adjustment or is it that smaller body movements…or is it that smaller body movements are required for adjustment? I think I’m right in saying that the physics of this is still debated. ---
**Author:** ![ModernPrimate](https://avatars.discourse-cdn.com/v4/letter/m/85e7bf/32.png) [@ModernPrimate](https://boards.straightdope.com/u/ModernPrimate)\ **Post date:** [September 21, 2011, 5:37pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/7 "2011-09-21T17:37:29Z")
Yes, try balancing on a bike when it’s not moving. Also, how can a wheel balance on its own after being pushed? There is definitely a force pushing it vertically. You shouldn’t be satisfied with just saying for example: “angular momentum” unless you have a coherent illustration of how it works. Yes it “wants” to continue going forwards, but it doesn’t “know” that if it falls to the side that it won’t be able to do that. It’s not as simple as it may sound at first. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [September 21, 2011, 5:39pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/8 "2011-09-21T17:39:09Z")
> [@BellRungBookShut-CandleSnuffed](#): > > _It_ doesn’t balance, you do. There’s a reason people just learning to ride fall over. Once you get used to the tiny cues that your bike gives you that you’re leaning too far in one direction, you correct for them before the shift really becomes visible. Your theory does not accout for the successful operation of [radio-controlled motorcycles,](http://www.youtube.com/watch?v=BIWzUApxYXA) for which kinesthetic cues are not transmitted back to the operator. In fact, the operator can take his hands off of the controls and expect the bike to continue merrily along without falling over. Something automatic and self-correcting is going on, independent of the rider/operator. ---
**Author:** ![YogSothoth](https://avatars.discourse-cdn.com/v4/letter/y/8edcca/32.png) [@YogSothoth](https://boards.straightdope.com/u/YogSothoth)\ **Post date:** [September 21, 2011, 9:41pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/9 "2011-09-21T21:41:20Z")
You read that [Cracked.com](http://Cracked.com) article didn’t you? I was thinking about posting that exact thing! I can’t believe we don’t know something so simple. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [September 21, 2011, 10:03pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/10 "2011-09-21T22:03:57Z")
> [@YogSosoth](#): > > You read that [Cracked.com](http://Cracked.com) article didn’t you? I was thinking about posting that exact thing! I can’t believe we don’t know something so simple. Hehe you got me…yes I did. I didn’t want to link the article because I thought people would just say “Dude it’s a humour article – they don’t know what they’re talking about” and not even think whether it’s true. Also that article does drop the ball somewhat on the _gravity_ entry (pun not intended). ---
**Author:** ![Tangent](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tangent/32/3098_2.png) [@Tangent](https://boards.straightdope.com/u/Tangent)\ **Post date:** [September 21, 2011, 10:15pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/11 "2011-09-21T22:15:51Z")
> [@Machine\_Elf](#): > > Your theory does not accout for the successful operation of [radio-controlled motorcycles,](http://www.youtube.com/watch?v=BIWzUApxYXA) for which kinesthetic cues are not transmitted back to the operator. In fact, the operator can take his hands off of the controls and expect the bike to continue merrily along without falling over. > > Something automatic and self-correcting is going on, independent of the rider/operator. [A similar (but non-RC) example that should be familiar to anyone who was a boy in the 70’s.](http://www.youtube.com/watch?v=eEUVm-Ja6lY&feature=related) ---
**Author:** ![Rachellelogram](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rachellelogram/32/8689_2.png) [@Rachellelogram](https://boards.straightdope.com/u/Rachellelogram)\ **Post date:** [September 21, 2011, 10:30pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/12 "2011-09-21T22:30:09Z")
> [@Machine\_Elf](#): > > Something automatic and self-correcting is going on, independent of the rider/operator. Clearly there’s a quantum relationship between your bike and a separate (but related!) anti-bike in an alternate universe. They communicate using bosons and Avocado’s delicious number. Fortunately, it’s not possible to explain the phenomenon to anyone having less than 2 Ph.Ds in physics, so it’s safe to turn on Jersey Shore reruns until your eyes explode into confetti, which then explodes into candy. Delicious eye candy. I’m sorry, what were you talking about? ---
**Author:** ![pabstist](https://avatars.discourse-cdn.com/v4/letter/p/e99b99/32.png) [@pabstist](https://boards.straightdope.com/u/pabstist)\ **Post date:** [September 22, 2011, 1:46am UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/13 "2011-09-22T01:46:08Z")
Have fun trying to figure out counter-steering. Basically, on a bicycle or motorcycle, you have to turn left before you go right, and vice versa. I ride both, and still can’t figure out why this is true. > **[Countersteering](https://en.wikipedia.org/wiki/Counter_steering)** > > Countersteering is used by single-track vehicle operators, such as cyclists and motorcyclists, to initiate a turn toward a given direction by momentarily steering counter to the desired direction ("steer left to turn right"). To negotiate a turn successfully, the combined center of mass of the rider and the single-track vehicle must first be leaned in the direction of the turn, and steering briefly in the opposite direction causes that lean. The rider's action of countersteering is sometimes Th... ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [September 22, 2011, 12:21pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/14 "2011-09-22T12:21:41Z")
> [@pabstist](#): > > Have fun trying to figure out counter-steering. Basically, on a bicycle or motorcycle, you have to turn left before you go right, and vice versa. I ride both, and still can’t figure out why this is true. > > [Countersteering - Wikipedia](http://en.wikipedia.org/wiki/Counter_steering) Countersteering is easy to understand. Two issues are at play: 1. Your handlebar inputs exert their effect at the road surface, where the tires make contact with the road. 2. If you want to turn, the bike[sup]\*[/sup] must first lean into the turn. #2 is true for any object balancing on its support. A person standing straight up wants to jump to the right? He has to lean right before he can begin moving in that direction; that means picking up his right foot to start falling right, or putting his left foot out to push himself to the right. Hovering helicopter wants to move right? First it has to roll right. So in order to _start_ a turn on your bike, the first thing you do is kick the tires out from under yourself. Want to turn right? OK, first, turn the handlebars to the _left:_ the tires steer out to the left, making the bike lean to the right. Once you’ve achieved a happy lean angle to the right, only then do you turn the handlebars to the right to actually begin following a right-curving path. Few bicyclists have ever heard of this concept (and few motorcyclists who have not received professional training), but they all use it. The ones who are consciously aware of the concept and adept at using it are the ones who are best equipped to execute evasive maneuvers that may save their lives someday. [sub]\* By “bike,” I am referring to the combined center of mass of the rider and the bike.[/sub] ---
**Author:** ![Fubaya](https://avatars.discourse-cdn.com/v4/letter/f/c2a13f/32.png) [@Fubaya](https://boards.straightdope.com/u/Fubaya)\ **Post date:** [September 22, 2011, 4:06pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/15 "2011-09-22T16:06:50Z")
I always assumed bicycle balance was from air pressure. Have you ever took something that blows air, pointed it straight up and sat a ball on top of the blowing air? The ball levitates. since the air is moving on each side of it, it doesn’t fall to the left or right. Bernoulli, etc. Same thing with a bike, I thought. Do they balance in a vacuum? ---
**Author:** ![silk1976](https://avatars.discourse-cdn.com/v4/letter/s/8edcca/32.png) [@silk1976](https://boards.straightdope.com/u/silk1976)\ **Post date:** [September 22, 2011, 4:15pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/16 "2011-09-22T16:15:20Z")
[Gyroscopic precession?](http://en.wikipedia.org/wiki/Precession) “Gyroscopic precession also plays a large role in the flight controls on helicopters. Since the driving force behind helicopters is the rotor disk (which rotates), gyroscopic precession comes into play. If the rotor disk is to be tilted forward (to gain forward velocity), its rotation requires that the downward net force on the blade be applied roughly 90 degrees (depending on blade configuration) before, or when the blade is to one side of the pilot and rotating forward.” ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [September 22, 2011, 4:30pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/17 "2011-09-22T16:30:27Z")
> [@Fubaya](#): > > I always assumed bicycle balance was from air pressure. Have you ever took something that blows air, pointed it straight up and sat a ball on top of the blowing air? The ball levitates. since the air is moving on each side of it, it doesn’t fall to the left or right. Bernoulli, etc. Same thing with a bike, I thought. Do they balance in a vacuum? It’s possible to ride slowly enough so that little to no breeze is created, and it’s possible to ride with the wind at your back, or in a cross breeze. I doubt it’s possible to balance in place during a hurricane. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [September 22, 2011, 4:36pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/18 "2011-09-22T16:36:34Z")
Not air pressure and not gyroscopic precession. Both of those forces are too small. If air pressure were the cause, how could you balance in even a small cross-wind? For gyroscopic precession, here’s an experiment you can do. Riding down a residential street, while standing on the pedals, you can easily angle the entire bike 20 degrees or so to the left or to the right, while still traveling in a straight line. If the force from gyroscopic precession was enough to keep you balanced, you wouldn’t be able to do that. It boils down to, a bicycle wheel doesn’t have enough mass or enough angular momentum to do much. You weigh more than the bike, so you can force the bike to lean. I’ll also point out that gyroscopic precession is not a _restoring_ force. It doesn’t tend to make the bicycle be upright. Once the bicycle is at that angle, it will want to stay at the angle it’s at, so it wouldn’t help you get back to upright. ---
**Author:** ![Terr](https://avatars.discourse-cdn.com/v4/letter/t/839c29/32.png) [@Terr](https://boards.straightdope.com/u/Terr)\ **Post date:** [September 22, 2011, 5:10pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/19 "2011-09-22T17:10:35Z")
Hm, when you’re riding a bicycle, you constantly counteract the bicycle leaning to one side or the other by turning very slightly into the lean - that is, if it starts leaning to the right, a slight turn to the right and vice versa. The same cannot be done while standing still because turning into the lean won’t correct the lean unless the bicycle is moving. But you can see it when people are standing still on the bike (or moving _very_ slowly) and are trying to balance - you see exaggerated turning of the wheel. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 22, 2011, 5:15pm UTC](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060/20 "2011-09-22T17:15:51Z")
Gyroscopic precession, positive caster, and user input all contribute together for the effect. It’s not a mystery. Bicycles are unstable, but the degree of instability decreases as it goes faster, because the physical forces play a larger part. But without user input it would fall over. People can develop the skill of staying upright on a bike without moving at all. **ZenBeam** , you can’t tilt a bicycle like that without changing the CG by shifting your body. The tilt you are talking about is just your perception of what an upright bicycle is. In fact, based on the CG, the bike is not titled at all. And you could go far more than 20 degrees if the shape of the tires doesn’t take you off course. [Next page](https://boards.straightdope.com/t/my-idea-for-how-a-bicycle-balances/597060.md?page=2)