- [Narrator] Countersteering is an amazing technique
used by many bike riders
and is very useful in making a quick turn,
and doing some bike stunts like this.
At first, countersteering looks counter-intuitive.
You turn the handlebars to the left,
but the motorcycle makes a quick right turn.
What are the physics behind this strange phenomenon?
Let's explore.
Before understanding the physics behind countersteering,
we need to understand the physics
behind normal motorcycle steering
and no-slip wheel condition.
First, let's explore what is meant
by this no-slip condition.
The wheels are always trying to attain a non-slip condition,
which means that the wheels should have no relative motion
with the road.
Since the road is at rest, the wheel contact point
should have zero velocity.
But how is zero velocity possible for a moving wheel?
It is possible because the wheel has two kinds of motion,
a translational motion along with the vehicle
and a rotational motion on its own axis.
You can see that it is possible
to make the resulting velocity zero at the contact point,
since the translational and rotational velocities,
are in opposite directions.
In normal steering, to make a right turn,
what we do is just turn the handlebars towards the right
and lean the motorcycle inwards.
Let's analyze the normal steering operation
in a step-by-step manner,
to understand the physics behind it.
Assume that even after turning the handlebars,
the vehicle moves straight ahead.
Here, if you check the front wheel,
it will not meet the no-slip condition,
since the wheel and vehicle velocities
do not cancel each other out.
The only way to solve this problem
is by making the translational velocity inclined as well.
This is possible when the whole motorcycle makes a turn
around an instantaneous center.
The instantaneous center should be at the intersection
of both the wheels' normal lines.
It's clear that when the motorcycle makes a turn
in this manner, both the wheels easily satisfy
the no-slip condition.
In short, the no-slip condition
forces the motorcycle to make a turn.
However, a centripetal force is needed
for any object to make a turn.
This centripetal force is provided by the frictional force
between the tire and the road.
Let's do the torque balance of the motorcycle,
at one point during the turn.
You can see that the vehicle is not stable in this position.
The torque produced by the frictional forces
will turn the motorcycle down.
The only way to balance this torque
is by leaning your motorcycle inwards.
You can see how the gravitational and normal forces act
in the inclined motorcycle position.
This will produce another torque, which can counter
the torque formed by the centripetal force.
This is the way you normally turn the vehicle.
You turn the handlebars to balance the torque produced
by the centripetal force, just lean the motorcycle.
Here, the rider has to adjust his body position
to achieve the lean of the motorcycle.
Note that the handlebars turning and the leaning operation
happen simultaneously and are in perfect balance.
How is countersteering different from normal steering?
In countersteering, you turn the handlebars,
however, you do not lean the motorcycle.
Obviously, this is an unstable condition.
The torque produced by the centripetal force
will topple the motorcycle in the opposite direction.
In short, the motorcycle achieves a lean
in the opposite direction for a moment.
This lean is sufficient to achieve a perfect turn
in the opposite direction.
One thing to be noted here
is that during the lean operation,
the driver cleverly adjust the angle of the handlebars
so that it is suitable for a perfect no-slip condition.
In short, in normal steering, the lean of the motorcycle
is achieved by shifting your body weight.
In counter steering, the lean is achieved
by the motorcycles instability
caused by the centripetal force.
Obviously, countersteering is a quicker operation
but slightly risky.
If you don't steer the handlebars back to the proper angle
during the leaning operation,
you are going to fall down.
This is why proper practice is needed
to master this instability steering trick.
Countersteering is quite handy
to avoid sudden obstacles in the road.
Let's see how it works in practice.
- The trick of countersteering is that you turn the handle,
but don't lean.
Also practice it well.
(upbeat music)
- [Narrator] It is clear from this demonstration
that by turning the handlebars to the left,
the rider was able to shift the motorcycle
to the right side.
Obviously, the counter steering is a quicker method
to avoid sudden obstacles.
We hope you have enjoyed the science behind countersteering
and wish you all the best in mastering this art.
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