I am giving the right handlebar a steady push. I am not turning the handlebars clockwise in any way. And yet I am turning left. According to the claims in the thread, I am not doing something wrong; I am doing something impossible.
It sounds like you are describing what was happening while you were actively traveling through the turn, whereas the experiment I described upthread is about what happens at the outset to get the turn started.
That being the case, your body must have been leaning off of the bike toward the inside of the turn. When you do this, the bike wants to turn harder, and some forward push on the right grip is necessary to prevent it from spiraling into a tighter turn than you would like. This happens to me on a 600-pound motorcycle, where my own 180-pound mass has limited effect on the location of the combined center of mass. If you were on a ~25-pound bicycle, then even a slight lateral movement of your body pretty much dictates where the center of mass is and will have a huge effect on steering behavior.
No. The centripetal force is directed horizontally; it cannot add to the downforce. If you and your bike weigh 400 pounds, the downforce against the ground will be 400 pounds. That’s all there is to it. It doesn’t matter if you’re going in a straight line or turning, or if you’re leaning off this way or that, or if the turn is banked; the downforce can only be 400 pounds because gravity is only pulling you down toward the ground with 400 pounds of force.
Chronos, you need to test it by filming the bike from the front as you turn. Countersteering on a bike is very subtle and using your method does not preclude you from unconsciously cheating. You don’t test countersteering by examining your physical inputs (though it can be enlightening to do that), you test it by checking whether your front wheel is very subtly and briefly turned opposite to the direction of lean. We are talking only a few degrees.
Also I think the statement that you can’t lean without countersteering is misleading. You can ride a bike handsfree, using your hips to move the bike underneath you. I think you’ll find though, and I’m not about to test it myself, that the countersteering still happens, but that it is managed by your hips rather, than directly moving the bars.
Not even a few degrees. In this particular case, about half a degree. That’s from the Wikipedia page on countersteering, and shows the results from a computer simulation of bicycle behavior at 13 MPH:
Well of course the fork is going to rotate a small amount prior to the turn. The fork is always rotating a small amount, even when going straight. That’s part of what makes bicycles stable.
And we’re moving the goalposts here, anyway. If I’m not giving the bicycle any counter input, then I’m not countersteering. At most you could say that the bike is countersteering despite me.
This your problem. You are riding too slowly. At low speeds the countersteering is buried beneath all the constant corrections. The signal gets lost in the noise so to speak.
At higher speeds the fork moves much less, and countersteering is much more noticeable.
Try riding as fast as you can, and then while riding with just your right hand, start a turn to the left. If you are going fast enough, you will notice that you need to pull with your right hand to start a left turn.
If you like. The fact is that countersteering happens, whether you are conscious of it or not is beside the point. And yes, the movement gets lost in the small corrections made at low speed. Try this experiment, ride at a reasonable speed, say 10-15 mph, then with out trying to or thinking about leaning, just turn the handlebar abruptly to the right. Which way does the bike fall? Now, if you wanted to make an aggressive turn to the left, which way do you think you’d have to turn the handlebar to get that turn happening? The same thing happens with gentle turns but it is so subtle and instinctive for an experienced bicycle rider that you just don’t realise you’re doing it.
Watch this video. Note that the countersteering movements are exaggerated for demonstration purposes.
If you think of it more as pushing the bike down with the inside handle bar, you may become more conscious of it. When I turn a bike, my inside hand pushes on the handlebar, e.g., for a turn to the right, my right hand pushes the right handle bar which causes a slight turn of the front wheel to the left. Once the lean angle is established, I relax the push on the right handle bar allowing the front wheel to follow the turn. Depending on the stability of the bike there may still be some noticeable push on the right bar to maintain the lean angle and prevent the bike’s tendency to straighten up. On my mountain bike, which is more stable than my road bike, the countersteering is more noticeable.
This method of riding using pressure on the inside handlebar is why I find it a bit difficult to indicate with my arm and turn at the same time, sure I can do it, but I have a lot more control with my inside hand on the bar so I will typically indicate before a turn and then have my hand back on the bar during the turn.
Another thought is that if you are not a particularly confident rider, you may be unconsciously waiting for the bike to fall in one particular direction as part of its constant wobble of stability and then you just go with it. In this case the only movement of the handlebar you’d be conscious of is the movement in the direction of the turn to prevent the bike from leaning too far. In this case the bike’s inherent stability is providing the initial counter-steer.
Another time you may be able to see counter-steering in action more prominently is when transitioning from cornering in one direction to riding straight or cornering in the other direction. If you just turn the handle bar in the desired direction you will lean further over and fall off, you initially need to turn the handlebar further into the turn (or for a very stable bicycle, allow the handlebar to turn further into the turn) in order to force the bike to lean in the opposite direction. Note that the more stable a bike is the more it will do this on its own, but in that case you should be more aware of counter-steering just to keep the bike established in the turn.
Hey! Are you calling me and/or my bicycle fat? 
Anyhoo, did you not just say this:
For centripetal force, read lateral G force if you like. Let’s eliminate a few variables and say it’s flat ground, and the bike’s cornering path is a perfect arc. Also the grip is perfect, and we’re ignoring energy transferred in other ways (heat, sound, tyre deformation, electromagnetic radiation etc.). No matter what the (successful) cornering technique, some of the bike and/or rider’s mass needs to lean into the turn or the lateral G forces will flip the rider over towards the outside of the turn. Some of that lateral G will go into downforce in the tyres, and some will go into maintaining the potential energy of the centre of mass of a system that’s gone outside its own footprint, i.e. keeping the bike/rider from falling on the ground towards the inside of the turn.
How about the same setup but in a car? Can’t lean the car into the turn, and the effect of the driver moving around is negligible. Here the lateral G forces of cornering go into compressing the outside suspension (energy is stored in the compressed spring), making the tyres’ cross-sections go a bit trapezoidal (again, energy stored in a spring-like thing), deforming the outside tyres through extra downforce (rubber spring thing) and raising the air pressure in the outside tyres through deformation (air spring thing). We’re ignoring tyre squealing and heat in the 4-wheeled example, but I’ve slipped tyre deformation back in. I think EM radiation can still safely be ignored. Compression of the suspension is a giveaway for additional downforce on the relevant tyres, and extra downforce means extra grip.
Sometimes I like to extrapolate to extremes to help me grasp a linear concept, so how about a motorbike rider on the Wall of Death? That’s about as leaned over as you can get, and although it’s not a flat, level surface like the previous two examples you could say it’s the same as an (impossible) bike with perfect grip leaning over so far they’re near-as-dammit horizontal. One centripetal force vector balances against gravity and keeps the rider from falling, and another centripetal force vector adds downforce to the tyres. It also adds downforce to the rider’s intestines to such an extent that good bowel control is a pre-requisite for this discipline.
Of course I could be labouring under a misapprehension here - do correct me if I’m wrong. I did originally think that centripetal force could only hinder grip when cornering on a flat surface as its origin is 90 degrees to gravity, but it’s got to go somewhere - the universe demands balance…
I just did a short ride on my mountain bike, reinforcing some things mentioned in this thread:
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If you are rolling in a straight line and deliberately rotate the handlebars even a very small amount in either direction, it’s glaring evident that the bike immediately leans the other way - you must quickly rotate the handlebars that way to avoid a fall. You can maintain the lean - resulting in a turn - or stop it and continue straight.
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If you limit yourself to gentle turns at low speeds, it’s easy to overlook the countersteering that’s happening. The inevitable minor balance instabilities result in small leans left and right; these are associated with small, easy-to-overlook handlebar rotations in the opposite direction to the lean. If you wish to turn, just wait for a “random” lean in the desired direction and avoid correcting for it. Because the countersteering was subtle and not something you deliberately did, it’s easy to convince yourself that no countersteering was involved.
When the original point was “if you want to turn left, you have to turn the handlebars right”, then it’s not beside the point at all if you don’t have to do that.
And I don’t see the point of an experiment consisting of a deliberate crash. I don’t want to fall over when I turn, so why would I try something that makes me fall over, in order to prove a point about the turns where I don’t fall over?
This is important. unskilled riders (or riders who are not particularly aware of countersteering) have a difficult time riding with a high degree of precision/control.
There is a stretch of road on the Tennessee/North Carolina border called Deals Gap, AKA “Tail of the Dragon.” It’s 11 miles long and has 318 turns in it, including numerous 2nd-gear hairpin turns and slaloms. I’ve ridden through there more times than I can count, and riders who have not consciously learned/practiced countersteering are easy to spot, in that they ride at a snail’s pace and seem to struggle with making the bike turn when they want it to.
The goalposts are right where they started. I’ve been arguing all along, repeatedly, that:
[ul][li]a turn can only be initiated by a countersteer, and[/li][li]that countersteer is done either by direct handlebar inputs from the rider’s hands (conscious or not), or by the bike’s self-stabilizing steering geometry, when the rider leans the bike away from the turn by shifting his body weight to the inside of the turn.[/ul][/li]
No, it won’t. It can’t. Since the bike is not accelerating in a vertical direction, the sum of forces in a vertical direction must equal zero, which means the vertical load on the tread must equal the bike’s weight.
The tires on the outside of the turn become more heavily loaded, but the tires on the inside of the turn become less heavily loaded by an equal amount. In the extreme case, the tires on the inside of the turn will lift off of the road - in which case the tires on the outside of the turn will bear all of the vehicle’s weight (and nothing more). The sum of the downforce on all four tires must exactly equal the car’s weight.
We need to be careful not to muddle our directional references. I will continue to use “vertical” to mean a direction parallel to the gravity vector, “down” to mean a direction toward the center of the earth, and “weight” to mean the pull of gravity on the bike/rider. Using these conventions, the vertical tread loading is still exactly equal to the weight of the bike/rider. As you’ve noted, with a banked turn such as the Wall of Death, yes, there is a component of centripetal loading that is normal to the riding surface and can therefore increase the available traction.
When turning on a flat/horizontal surface, there is no component of centripetal loading that is normal to the riding surface, regardless of whether you’re hanging off of the bike or not.
So you accept that counter-steering occurs to initiate the lean, either by rider control or by the bike’s movements?
You don’t crash it, you observe the result of your actions then correct the situation. Just like Xema describes doing above. All you are doing is initiating a turn.
As another answer to the OP, the way you go round and exit a turn can be very different on a motorbike because of the control the throttle gives you. Main difference being the throttle lets you straighten up a bit quicker than you otherwise would.
I don’t think you can pedal furiously enough on a bicycle to do the same thing.
For tight turns at modest speed and intelligent gear selection, hard pedaling can be useful to stand the bike up out of a turn, but yes, nothing like using an engine to rapidly pick up speed and exit a turn.
Are you trying to make some pedantic point?
We all know that you can successfully ride a bike, even around turns, with your hands completely off the handlebars (look, mom!). Even riding without hands, you have to countersteer to get into a turn. The fact that you’re countersteering without using your hands to push on the handlebars doesn’t mean that it’s not countersteering. To countersteer, you have to make the front wheel point briefly in the direction opposite the turn you intend to make. The front wheel is directly connected to the handlebars, so turning the front wheel is also turning the handlebars, whether it’s with your hands or with your hips.
You’ve got this backward.
Imagine a broomstick, balanced vertically on your palm:[ul][li]If it starts to fall to the left, and you don’t want it to, you have to move your palm to the left to get back under it. [/li][li]If it’s stable/stationary and you want it to fall to the left, the first thing you have to do is move your palm to the right to make it fall to the left.[/ul]Now think of the bicycle/motorcycle:[ul][]If it starts to lean to the left and you don’t want it to, you have to move the contact patches to the left to get back under it; you do this by steering to the left. []OTOH, if it’s traveling in a stable straight line and you want it to lean to the left (as for a deliberate left turn), the first thing you have to do is move the contact patches to the right to make the bike lean to the left; you do this by first steering to the right.[/ul][/li]
Self-stabilizing steering geometry is stable because it tends to turn the handlebars in the direction the bike is leaning.
Stand on one foot. Now lean your upper body to the left. Your entire body will want to fall to the left. You don’t need to move your foot to the right to lean left. Your body isn’t a broomstick.
On a bicycle, you can lean the bike just by body leaning. On a motorcycle at low speeds, you can do it to if it’s a light enough bike. On a heavy motorcycle or at higher speeds, there’s just too much mass and momentum for it to be a practical way of leaning the bike.
If you turn a bicycle with no hands, the wheel will tend to naturally countersteer a bit as you initiate the lean. If you want to turn a bicycle without countersteering you are going to have to hold the handlebars.
Absolutely correct, your body isn’t a broomstick. When you’re standing on one foot, you are kept stable by muscles in your leg that are managing forces on that foot. Said foot has significant width, versus the negligible width of the pointy end of a broomstick.
Want to lean your body to the left? You will adjust your muscles so as to decrease the force on the left side of your foot, and/or increase the force on the right side of your foot. Now the net upward force of the ground upon your foot has shifted to the right of your center of mass: the up-force from the floor is now exerting a moment about your center of mass that will cause you to rotate about your roll axis to the left.
If you want a more apt comparison with the broomstick-on-your-palm example, take your body and put it on a single ice skate. What to lean left? You first have to steer that skate out to the right so the ground can apply a torque to you that rolls you to your left.
If you are riding in a straight line and lean your body to the left, the bicycle/motorcycle will (at first) lean right. Or do you think Newton was just plain wrong about that?