This discussion centers on the mechanics of changing direction on a motorcycle, specifically the role of counter-steering versus body weight shifting. Participants agree that while counter-steering is the most effective method for initiating a turn, shifting body weight can influence the motorcycle's center of gravity and lean angle. The conversation highlights the importance of the point of force application, noting that pushing below the motorcycle's center of mass generates less torque and is less effective. Ultimately, the consensus is that while body weight shifting can impact direction, it is not a substitute for counter-steering, especially at high speeds where gyroscopic forces come into play.
PREREQUISITESMotorcycle enthusiasts, riding instructors, and individuals interested in improving their motorcycle handling skills will benefit from this discussion.
Why does self correction that steers the bike go away at high speeds? Isn't it due to gyroscopic effects from the wheels? Or is it because of the camber thrust?rcgldr said:At high speeds the self correction that steers a bike into the direction of lean goes away and instead the bike tends to hold a lean angle without counter-steering used to change the lean angle. The mathematical models call this "capsize" speed, where the modeled bike falls inwards at very slow rate, so slow that it's imperceptible. The mathematical models may not take into account that the contact patch shifts inwards due to deformation, which would counter the slow inwards falling. The actual effect reported by motorcycle racers is that once leaned, a bike at high speeds tends to hold the lean angle, and the rider has to counter-steer to make any change in lean angle, and that weight shifting has no perceptible effect. The amount of effort to counter-steer increases as speed increases, and at these high speeds, it takes a significant amount of counter-steering effort to change lean angle.
It's due to gyroscopic effects becoming dominant at high speed. At "normal" speeds, the steering geometry results in self corrective steering that tends to return a bike to a vertical orientation, but at high speeds, the tendency is to hold the current lean angle. At "normal" speeds, a small amount of counter-steering is needed to overcome the steering geometry to hold a lean angle, while at high speeds, virtually no rider input is needed to hold a lean angle. At high speeds, a rider has to use counter-steering to make any change in lean angle.Erunanethiel said:Why does self correction that steers the bike go away at high speeds? Isn't it due to gyroscopic effects from the wheels? Or is it because of the camber thrust?
A bicycle or motorcycle has to be leaned inwards in order to keep from falling outwards during a turn. Regardless of speed, counter-steering to setup the initial leaning motion is always needed. The unicycle guys understand this, since there's no steering reaction to lean as there is with a bike.GeorgeX45 said:As a motorcycle rider you might start from the way that you initiate a turn. At low speeds, when the rotational inertia of the wheels is low, you turn the front wheel to the right to turn right. At high speeds, when the rotational inertia of the wheels dominates the behaviour of the motorcycle, you turn the front wheel to the left to turn right. When turning the rider moves on the motorcycle to lower the centre of gravity which it is suggested increases the traction (see the book by John Surtees) although this may have more to do with preventing the motorcycle from flipping outwards by reducing the turning moment about the tyre contact patch - watch what happens when the contact is lost and the motorcycle starts to slide versus being high sided.