What causes a motorbike speed wobble?

Much of a motorbike's cornering comes from the angle of the tyre in relation to the road, and very little from the angle of the handlebars, i.e. as the bike leans over it will tend to steer in the direction of the lean.

The wobble happens at an oscillating frequency of the motorbike that's a product of the:

• height of the bike
• centre of the mass of the bike and rider
• distance of the bike's centre of mass from the rear wheel
• lateral stiffness of the front tyre when cornering.

A wobble can begin to occur when an irregularity in the road surface, or something the rider does, causes the bike to buck to one side. For example, running over the side of a bump can cause it, as can accelerating because the bike will move through zones where the vibration is a harmonic of the natural oscillation properties of the bike. The rider applies correction in phase with the oscillation and this sends the bike the other way, and so on, and the oscillation continues until the rider can either gain control through strength, or the bike bucks the rider off. 

The best way to bring a speed wobble back under control is to close the throttle and hold on tight. Try to grip the tank with your knees so that you aren't thrown off and keep your feet on the footpegs unless you need to put a foot down to balance.

Professional motorbike racers will often accelerate through wobbles and you can see this on the track - they know how to deal with it, though. The safest way to deal with a wobble is to keep your speed down. It's unlikely that you will get a major speed wobble at highway speeds.

This video shows a selection of speed wobbles on a race track