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2.2 Minimum stable speed calculations WITH and WITHOUT hands on the handlebar:

Based on the Torso-Arms-Handlebar steering theory and a mathematical model developed by Ethier [1], calculations gave the following results for the minimum stable speeds of a 100cc motorcycle:

- WITH hands on the handlebar: 12,4 KPH (7.73 MPH)

- WITHOUT hands on the handlebar : 19,5 KPH (12.1 MPH)

These calculated stable speeds correlated with the speeds observed when riding. More importantly, this Torso-Arms-Handlebar steering theory explains what happens at slow speeds:

A) Above the minimum speed, control of the handlebar WITH hands on  is done automatically without jerky push-pull motions to stay upright, as it is experienced in day to day usage of 2-Wheelers at slow speeds.

B) The minimum stable speed WITH hands on the handlebar is lower than WITHOUT hands on the handlebar, because the rider can react on the front wheel even at standstill and, thus, without waiting for the speed to be high enough to generate gyroscopic and front fork geometry effects.

C) Moreover if the 2-Wheeler starts to fall, the rider will not simply stay vertical. He will rather react by leaning his torso in the opposite direction of the falling 2-Wheeler to avoid getting hurt. This will generate a higher centrifugal force to bring the 2-Wheeler back up faster. So the minimum stable speed WITH hands on the handlebar may be even lower.

[1] Pierre M. Ethier, “Dynamique des Vehicules à Deux Roues et Modifications les Rendant Plus Securitaires”, Master thesis in Mechanical Engineering, Universite Laval, Quebec, Canada, 1974, 109 pages.

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