The trail is the most important parameter that governs the dynamics of a two-wheeled vehicle. It is the basic element which defines the characteristics of the vehicle. A motorcycle with a high trail value is very directional and stable; a motorcycle with low trail value is extremely maneuverable but equally unstable and insecure. Let’s see what the trail is and how it affects a motorcycle.
The trail is the distance between the contact point of the front wheel on the ground and the projection point on the ground of the steering axis. The higher the distance, that it is usually measured in millimeter, the quicker the front bike will right itself. This means that when the front wheel hits a bump on the road, it will return to its trajectory thanks to the effect of the righting moment, creating stability. Therefore, we may state that, given equal parameters, an increase of the trail value results in greater vehicle stability.
On this basis, one would think that the greater the trail value the better the performance of the vehicle but it is not true… An increase of the trail value reduces the agility of the vehicle and at the same time it requires more strength to be applied to handlebars to change trajectory. This is why we must find the right compromise between the trail value and all other factors and adjust certain characteristics rather than others in order to obtain the best result.
In the field of traditional systems there are two different factors that influence the trail parameter: the offset (which is the distance between the steering axis and its parallel where the axis of the wheel lies), and the rake (the angle of the steering axis).
While in the first case we employ various types of base and head steering with different measures from the steering axis to the straight line that joins the two forks (The greater the distance the greater the offset), in the second case we rely on the geometry of the frame.
The center of gravity of the vehicle, the distance between the two wheels, the weight and the type of end-use of the vehicle also affect the choices that will get to the “ideal measure”. Needless to say, these values will be different in a Cross motorcycle and in a large displacement Chopper.
Consequently, the ideal trail is the result of a carefully studied combination of various factors. A perfect value does not exist yet, frame manufactures continue to try and mix these values in search for the best performance.
Now that we have seen the benefit and importance of the trial, we want to show how Vyrus employs the trial value and point out the differences with a traditional sports bike with similar characteristics. Adjusting the steering axis angle (consequently also the trail) on a Vyrus is simple and it can be done by lengthening or shortening the anti-dive rods by tightening or loosening the threads of the spherical joints that connects them. Basically, it is possible to transform a Vyrus from a racing bike to a Chopper and vice versa in a few minutes.
The incredible feature of Vyrus is offset equals zero, in addition, the steering axis angle is 18°, the trail value is 80 mm, it has a wheelbase of 1350 mm and finally a very high center of gravity. Although these measures would create serious problems in a traditional motorcycle also at low speed, in a Vyrus they create a very manageable and reactive bike that at the same time is also stable and very directional.