# Way the cornering forces are felt when riding a motorcycle

• Erunanethiel
In summary, when cornering on a motorcycle, the rider experiences a sensation of being pushed down onto the seat due to the centripetal force pulling the bike inwards towards the center of rotation. This is often mistaken for a centrifugal force, but in reality, it is a result of the centripetal force and the rider's own body weight acting in opposition to maintain balance. This concept is further explained in the linked article, which also debunks the myth of centrifugal force.
itfitmewelltoo said:
More interesting is what is called counter steering. The wheels, in particular, the front wheel, is a gyroscope. The angular momentum of the front wheel is significant. In order to turn left, the rider pushes forward on the left handle bar. The bike then leans to the left and the bike turns to the left. The effect is more pronounced as speed increases and there is a transition speed below which the steering is as expected and above which angular momentum dominates

Erunanethiel
itfitmewelltoo said:
More interesting is what is called counter steering. The wheels, in particular, the front wheel, is a gyroscope. The angular momentum of the front wheel is significant. In order to turn left, the rider pushes forward on the left handle bar. The bike then leans to the left and the bike turns to the left. The effect is more pronounced as speed increases and there is a transition speed below which the steering is as expected and above which angular momentum dominates

That's not a gyroscopic effect - rather, it comes from the fact that if you turn the wheel to the right (by pushing the left handlebar forward), the wheels will steer to the right, out from underneath the CG of the bike. Since the wheels are now to the right of the CG, the bike "falls" to the left, initiating the left lean needed for the left turn.

itfitmewelltoo, Erunanethiel and berkeman
Erunanethiel said:
Everybody says when going around a corner on a motorcycle and leaning, you feel the g forces vertically (like pushing down on your spine) as opposed to horizontally when cornering in a car.
The rider feels a net force vertical with respect to the lean angle of the bike (if the rider is not leaning inwards or outward relative to the bike). If the bike is leaning at 45 degrees (and in a coordinated turn), then the rider and bike are leaning at 45 degrees, and the rider feels a net force that is also at 45 degrees, so the rider doesn't feel any sideways forces (if the rider is not leaning inwards or outward relative to the bike). This is essentially the same as a coordinated banked turn in an aircraft.

If the rider leans inwards on the bike, the rider would feel a torque and also a force that is not inline with the angle of the rider. The rider could lean to one side with the bike going straight (the bike leaned a bit the other way) and the feeling would be similar, just less force than if leaning inwards while cornering.

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Erunanethiel
The minimum force and acceleration is when the cycle is parked (or moving at a constant velocity). The acceleration due to gravity and the cooresponding weight.

The total acceleration when the bike is cornering, accelerating or decelerating on a straight line will always be more, the vector sum of gravity and cornering.

I believe that what they are referring to when they say the rider experiences 0.5g is that which is not due to gravity.

cjl said:
That's not a gyroscopic effect - rather, it comes from the fact that if you turn the wheel to the right (by pushing the left handlebar forward), the wheels will steer to the right, out from underneath the CG of the bike. Since the wheels are now to the right of the CG, the bike "falls" to the left, initiating the left lean needed for the left turn.
https://en.m.wikipedia.org/wiki/Countersteering

cjl said:
That's not a gyroscopic effect - rather, it comes from the fact that if you turn the wheel to the right (by pushing the left handlebar forward), the wheels will steer to the right, out from underneath the CG of the bike. Since the wheels are now to the right of the CG, the bike "falls" to the left, initiating the left lean needed for the left turn.
Oh, reading further in that link, "One effect of turning the front wheel is a roll moment caused by gyroscopic precession. The magnitude of this moment is proportional to the moment of inertia of the front wheel, its spin rate (forward motion), the rate that the rider turns the front wheel by applying a torque to the handlebars, and the cosine of the angle between the steering axis and the vertical.[10]".

Note the term "of turning the front wheel is a roll moment caused by gyroscopic precession."

itfitmewelltoo said:
As the link shows, you can countersteer at speeds slow enough so that gyroscopic effects are minimal. cjl is correct that the main effect is to move the front tire's contact patch out from under the COM, which causes the bike to tip in. There is a small gyroscopic effect as well at higher speeds, but only adds a bit in my experience.

cjl said:
That's not a gyroscopic effect - rather, it comes from the fact that if you turn the wheel to the right (by pushing the left handlebar forward), the wheels will steer to the right, out from underneath the CG of the bike. Since the wheels are now to the right of the CG, the bike "falls" to the left, initiating the left lean needed for the left turn.
Let's consider this intuitively. The classic presentation of the gyroscopic effect is a guy holding a spinning bicycle tire, sitting on a rotating chair. Compare the weigh of this bicycle tire and rotational velocity to the weight and rotational velocity of a motorcycle wheel at 40 mph. The bicycle pales by comparison. It can hardly be said that the precession of that motorcycle wheel is negligible. Clearly it is not.

And, the phenomena does not occur at low speed. There is a crossover speed at which the steering changes from as expected to counter steering. As speed increases, the effect becomes more pronounced. What has changed? What has changed is the rotational velocity of the wheel.

itfitmewelltoo said:
Let's consider this intuitively. The classic presentation of the gyroscopic effect is a guy holding a spinning bicycle tire, sitting on a rotating chair. Compare the weigh of this bicycle tire and rotational velocity to the weight and rotational velocity of a motorcycle wheel at 40 mph. The bicycle pales by comparison. It can hardly be said that the precession of that motorcycle wheel is negligible. Clearly it is not.

And, the phenomena does not occur at low speed. There is a crossover speed at which the steering changes from as expected to counter steering. As speed increases, the effect becomes more pronounced. What has changed? What has changed is the rotational velocity of the wheel.
Do you ride? What do you ride?

itfitmewelltoo said:
Oh, reading further in that link, "One effect of turning the front wheel is a roll moment caused by gyroscopic precession. The magnitude of this moment is proportional to the moment of inertia of the front wheel, its spin rate (forward motion), the rate that the rider turns the front wheel by applying a torque to the handlebars, and the cosine of the angle between the steering axis and the vertical". Note the term "of turning the front wheel is a roll moment caused by gyroscopic precession."
The precession only exists while a torque is applied. Once the steering is completed, initially outwards to induce a lean, the precession stops since it's a reaction to torque, not angle.

itfitmewelltoo said:
There is a crossover speed at which the steering changes from as expected to counter steering.
There are two primary speed ranges, one below the speed of self-stability, one in the range of self-stability. For a mathematical model using razor thin tires, there is a third speed range (capsize speed), above which a bike would tend to fall inwards at an extremely slow rate, but with real tires, this speed range doesn't exist or only exists well beyond any speed that a bike could achieve.

Counter steering is in effect at all speeds. At slow speeds, it's much less noticeable as the steering input is very light. It's easier to see this effect in the case of unicycles, which don't have the self correction related to trail on a two wheeled bike.

itfitmewelltoo and berkeman
rcgldr said:
The precession only exists while a torque is applied. Once the steering is completed, initially outwards to induce a lean, the precession stops since it's a reaction to torque, not angle.

There are two primary speed ranges, one below the speed of self-stability, one in the range of self-stability. For a mathematical model using razor thin tires, there is a third speed range (capsize speed), above which a bike would tend to fall inwards at an extremely slow rate, but with real tires, this speed range doesn't exist or only exists well beyond any speed that a bike could achieve.

Counter steering is in effect at all speeds. At slow speeds, it's much less noticeable as the steering input is very light. It's easier to see this effect in the case of unicycles, which don't have the self correction related to trail on a two wheeled bike.

"Counter steering is in effect at all speeds."

Yes. It is one of a number of effects that vary with things like wheel weight and radius, the bike's weight, angle of the front forks, distance from front to back wheels, and ... things I haven't considered. Some of these are in opposition to the counter steering affect, what we might call "normal steering.". It is apparent that the counter steering affect decreases as speed decreases, becoming negligible. My impression, from riding around a parking lot, is that at 20-25 mph, "normal steering" is predominant.

It begs the question if why is there no apparent speed at which counter and normal steering component simple cancel out and make the bike simply unsteerable?

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