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5.5 Weight on the foot pegs and tightening up the knees:

5.5.1 Contribution:

- Standing up on the foot pegs improves steering of mountain bicycles and off-road motorcycles.

5.5.2 Limits:

- But this riding posture does not explain by itself the improvement in steering of 2-Wheelers.

- Tightening up the knees against the fuel tank is impossible on a bicycle that only has a small tube between the knees, but can be steered as easily as a motorcycle.

5.5.3 Better understanding:

a) Does increased CG height explain the steering improvement gained when standing up on the foot pegs?

The steering improvement gained at low speeds when standing up on the foot pegs could be linked to the center of gravity (CG) elevation of the 2-Wheeler/rider assembly. But even if an off-road motorcycle is lighter than a touring motorcycle, it can still be about 10 times heavier than a mountain bike (that can weigh less than 15Kg - 30Lb). The CG elevation of the assembly is thus clearly higher for a mountain bike than for an off-road motorcycle, so that the motorcycle should clearly benefit less steering improvement when riding on the foot pegs. But it's not the case, both benefit about the same from riding up on the foot pegs (or pedals).

When riding up on the foot pegs and for the same lateral shift of the torso relative to the 2-Wheeler’s chassis, a mountain bike chassis shifts laterally by action-reaction clearly more than an off-road motorcycle chassis versus the vertical. This should result in a quite different steering ability between the mountain bike and the off-road motorcycle, but it's again not the case.

So increased CG height hardly explains the steering improvement gained when standing up on the foot pegs or pedals.

b) Effect of standing up on the foot pegs according to the Torso-Arms-Handlebar theory:

According to this theory, an equal lateral shift of the torso versus the chassis controls the front wheel orientation the same whatever the difference in weight between a mountain bike and an off-road motorcycle. This theory can thus explain getting the same steering improvement when standing up on the foot pegs. According to this theory, steering when standing up simply means that the pivot letting the torso lean right or left is not at the rider’s low back height, but at the foot pegs' height. If the torso leans to one side around the axis at the foot pegs' height, the front wheel still is oriented in the opposite direction due to the Torso-Arms-Handlebar mechanism, just like when the rider sits on the saddle.

Steering standing on the foot pegs works so well that it does give the impression that it's by stepping more or less on these foot pegs that an off-road motorcycle is steered. In reality, stepping on the foot pegs simply lets the torso shift towards the opposite side, which lets the Torso-Arms-Handlebar mechanism work.

Moreover, an off-road motorcycle can be steered when simply sitting on the saddle just as a mountain bike can easily go straight when pedaling vigorously (or 'like madness') while swinging sideways from extreme to extreme. So it's not the simple fact of pushing on the foot pegs that steers and stabilizes a 2-Wheeler.

c) Tightening up the knees against the fuel tank and pressing on the foot pegs as if riding a horse:

Same thing when tightening up the knees against the fuel tank. We may have the impression that it steers the motorcycle, but it's obvious that a bicycle can be steered just as easily without having a fuel tank to press against.

People that have been riding horses are likely to fall under such an illusion. This is because horses can be driven by pressing with the knees or pressing on the stirrups, which the horse can feel and react to. It's thus easier to have the impression that 2-Wheelers react the same, but they are not animals and they sure can’t 'feel' the rider’s impulses.

d) Advantage of standing up on the foot pegs according to the Torso-Arms-Handlebar theory :

Still according to the Torso-Arms-Handlebar theory, the advantage of standing up on the foot pegs is to increase both the speed and amplitude of the torso leaning right or left and front wheel opposing orientations, in order to control the 2-Wheeler faster and more precisely.

If a rider rides standing on the foot pegs and suddenly has to go right, he may lean his torso towards the right but he can also use his legs and lean his torso further to the right. The result is that the front wheel is further oriented in the opposite direction to steer his vehicle faster according to the Torso-Arms-Handlebar theory. Furthermore, the 2-Wheeler chassis being leaned further (versus the vertical) towards the left, the front wheel is still further oriented in the opposite direction, just like the wheel of a wheelbarrow that orients itself towards where it's leaning (It’s the only way to 'steer' a wheel barrow).

So with the rider standing on the foot pegs, the 2-Wheeler (1) reacts faster and (2) can be stable at an even lower speed than WITH hands on the handlebar while sitting on the 2-Wheeler saddle. In servomechanism terms, the action and its result are well known as an increase of the 'Open-loop transfer function gain'.

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