My 16Yr old daughter understands it.........

Urban Myth? I'd say Gyroscopic effort is very real. Just grab a spindle of a spinning wheel and try and turn it - it's hard and the heavier or faster the wheel's turning the more force needed..

The larger diameter and/or greater weight or speed, require a bigger input to move and counteract against.

Lightweight wheels are a big deal and is why race teams spend so much and manufacturers of performance bikes put effort into lightweight wheels/discs/tyres and then there's wheel diameters. The change from a 16" front wheel being too easy to turn to a 16.5" GP front being right to a 17" being slow is all a result.. As for a heavy 21" with high windage and you need more force to make the thing move or turn.

GULG - You sound like a man who knows and just try a 17" front on the Ten' and feel the difference. That's gyroscopics..

There are many different effects all of which have their part in how and why a motorcycle behaves as it does. It is certainly not correct to isolate one effect to explain cause and effect.

Certainly there is a rolling cone effect to be considered, certainly the wind and aerodynamic properties of bike and rider will provide input into the mix. Centrifugal/centepetal forces acting against the frictional resistances provided by the surface. Gyroscopic effect is part of this - clearly demonstrable and certainly not a myth.

What I always do, with strong sidewinds and passing a large truck: next to the truck hold the throttle, the moment I pass the truck open it up when the wind comes in full speed. It always works.
Greetz, Hans.

Sorry, maybe I need to elaborate a little, in terms of counterster and the upright ability of a bike, which is ofen explained by centripitle or gyroscopic forces, is a myth. Of course these forces are present and are many many more, but in such small quantities that they do not have a noticable impact to the handling of a normal road bike. It's relaitive, In fact, as you are all so interesed I'll post up the full explanation of the forces on the front wheel of a motorcycle during a turn, but the OP was about wind effect and to be honest turning forces (and those involved in a change of direction) have little to do with the effects of a headwind, my intial diversion into turning forces was to explain the error of one reply.

I beg your pardon?

That's a very bold statement. It's also, how can I put it...wrong. Yeah that's the word ;)

I await your explanation with interest.

It is when you take it out of context. The discusion is about the effects of a side wind on the motorcycle, so yes Gyroscopic effect is an urban myth in this respect. So no, the statement is not wrong.

if the statement was made regarding the general handling of a motorcycle then yes, you are correct, but that isn't the topic, is it.

Ok then, I'll be a bit more constructive than my last post. But I don't think I'm taking this out of context...

I struggle to read that as being specific to cross-winds and not talking about morotcycle handling in general. And yes the person who first mentioned countersteering was wrong in saying it had anything to do with leaning into the wind. But you didn't *correct* him, because what you said wasn't correct.

Camber thrust, or what you refer to as 'rolling cone effect' is very real, and is what causes a motorbike which is leant over to follow an arc rather than a straight line.

However, in order to generate camber thrust, you need to get the bike leant over, and you absolutely, definitively cannot change the lean angle of a bike* without making use of gyroscopic forces.

Wheels and tyres are pretty heavy things, particularly on production bikes. They also have most of their mass concentrated out around the rim/tyre. Which means they have a large moment of inertia about the wheel spindle. And they are spinning pretty fast, so there is a lot of gyroscopic effect going on. If you think otherwise, ask why so much is spent on lightweight wheels for racing.

This means that a motorcycle with both wheels pointing straight ahead wants to stay upright and carry on in a straight line. This is quite a useful thing, as it means we can get beyond the end of our streets without falling off. People have built bicycles with contra-rotating flywheels to cancel out the inertia of the wheels, and they're pretty unrideable.

Where you go wrong is in your assumption that because you can get a motorcycle to turn, the gyroscopic effects are insignificant. In doing this, you are ignoring the fact that you can turn the front wheel, and a fun little phenomenon called gyroscopic precession.

Anyone that's been to a science museum on a school trip will have experienced this (and this is way before A-level age). The old experiment of putting someone in a swivel chair, holding a spinning bicycle wheel out in front of them by the spindle, and observing that tilting it to the left or right causes the person, and chair to revolve. You're doing exactly the same thing to change the lean angle of a bike, except this time you are rotating the wheel around a (near) vertical axis - the steering head - which is causing the bike to revolve around a horizontal axis (the line between the tyre contact patches). To make the bike tilt left, you steer right, and vice versa. This is what is referred to as counter-steering, and like it or not, unless you only ride at walking pace, you *are* doing it.

To summarise:

- Gyroscopic effects allow you to change the lean angle of a motorcycle.
- Camber thrust causes a leant over motorcycle to follow an arc rather than a straight line.
- Both are significant.


As to the point of your OP...I'm still digesting that. There's some things in there which jar a bit with me, but I'm trying to figure out whether the problem is with the physics, the explanation, or the ignoring of other factors.


*at a significant rate. You can get a bike to change its lean angle by energetic use of your bodyweight, but not quickly.

That's better, I see now where you are coming from, and yes you explanation agrees with my understanding.

The post you reffered to was (in hindsight a mistake) a brief and broad attempt to direct the terms used, into the correct area of discussion, not a full description of the forces that act upon a bike during a manouver.

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To add to the OP, and the 'spoon' explanation, looking at saling craft (the ones with no parts in mechanical perpetual motion). Have you ever wondered (probably not) how they can sail into the direction of the wind, yes we all know it's by tacking, but how do you convert a force pushing you (say for instance) south into a northerly travel direction?

It is the same principle (no I'm not suggesting that a motorcycle has a mast or sails, or is indeed amphibious, has gills, scales or rope), and this is very simplistic (as I don't fully understand the mechanics of it, but I do understant the principle - Maybe SteveD can add to this?) in that you fill a sail with air, and this forms a dome on one side and a shorter surface on the other, the trick is then to get the wind to pass along the sail (not blowing it along like an old can of coke) which causes the air to pass over the curved surface faster than the air passing over the 'flat' or short surface (Technically it's not flat as it curves inward due to sails being made of fabric/plastic/thin stuff). The speed differential creates lower pressure on the curved surface with normal pressuer on the 'flat' surface. The net result is that the sail (and the attached water craft) will move from the high pressure area to the lower pressure area propelling the boat forward, while the wind direction is coming from the side. In the same way the wing of an aircraft creats lift, or a 'spoiler' on a car (racing, F1 or otherwise) uses the same principle to creat downward force to press the car onto the road.

In the case of the OP, and in particular Toms comment, I would suggest that the OP is correct to a point, and that point would be as the cross wind speed approaches the head wind speed. At which point the effects of pressure would be overcome by the pure directional force of the wind over the available grip and mass of the motorcycle. And thus you would become the tumbling coke can.... or rolling truck, tree or building (clearly your bike would not turn into a 4 storey block of flats, or a 40ton truck, or grow branches, or develope a sugary fruit-ish flavoured drink inside it's engine)

I'm happy to debate these points, not least as it helps me solidify my understanding but if people are going to make statements that contain no explanation as to why they disagree then I have to ask what the point of it is ? (the statement), and how it can benifit others understanding, or substantiate the point they are making, especially those that are reading this as new understanding or learning. Questions are fine, and good, and help everyone.

I suppose there is always a danger in attempting to explain things by a one way conversation (like a forum) as things get mis-understood, mis-read, mis-quoted, but this shouldn't stop people from being bold and attempting to spread the knowledge. If you are not interested then you don't have to read it. Some folk are happy to just get on the bike and ride, others like to add shiney bits and polish, some like to use them to get to work, other like to learn a bit......

this thread seems to be a bit like herding cats :D bet you glad you offered the snippet in the 1st place eh Daz :P
I liked it by the way and cant wait to try the knee out tip.