The motivation for this week’s article was an incident I experienced last week, which is something that all riders will experience at some point — speed wobbles. They can often end in a highside crash, but there are some ways to avoid them from happening. Before I give my input on the avoidance of and getting through a speed wobble, here is some information about them:
Speed wobbles are most often defined as a rapid side-to-side movement of the wheel, which can quickly increase in speed and intensity. An important dynamic of a motorcycle related to speed wobbles is the front-end naturally trying to return to center, called positive dynamic stability. When combined with low pressure in one or both of the tires, and especially when a rider is turning, the wobble cycle can start.
What happens is the underinflated tire can easily bend to the side and then the front end will naturally try and return to center, but then the underinflated tire bends again and this cycle continues. The cycle and intensity can quickly amplify, causing a rider to lose control. Also, a rider using too much pressure on the handlebars or using the front brake when there is a front-end wobble can increase the speed and intensity of a wobble.
There are other causes where the front tire quickly goes to the side that can cause the positive dynamic stability wobble. Some of them include hitting a pothole, getting caught in or on a rut, or other areas where the pavement is not flat and smooth.
Another type is where the front end only goes through part of a cycle. This happens when there is a quick turn and then the straightening of the front wheel. This can happen when trying to land a wheelie or when a rider briefly loses traction in the back tire and then quickly regains traction, often bucking the rider off. Additionally, although most often they occur, or are most often noticed in the front wheel, they can also occur in the back wheel.
These are the basics behind a speed wobble and in an upcoming article there will be some ways to avoid and get through a speed wobble discussed.