Steering is a system of components and linkages which allows the vehicle to follow the desired path. All vehicles have definite steering except the rail transport which use railroad switches to provide steering function.
Following the terms which are used for defining the steering of motorcycle
- It is the angle between the steering axis and the vertical (refer fig. 1).
- Steering axis is the axis around which the front wheel assembly swivels as we move the handlebars (left or right).
Significance of rake –
- Rake angle is directly proportional to the stability of the bike; which means higher the rake angle more will be the stability of the motorcycle ,lower the rake angle less will be the stability of the motorcycle.
- Less rake means quicker steering, which means when we want the bike to go round a corner or to avoid an obstacle we turn the handlebar to the left or right and within short span of time we have changed our direction.
- More rake means slow steering.
Note: Rake angle is also called “Caster angle” or just “Rake”. Below is figure 1.
- The distance between the point obtained from extrapolating the steering axis towards the ground and the contact patch of the tyre is trail of a motorcycle.(refer fig. 1 )
- contact patch is the point where the tyre meets the ground.
- Higher the rake means more will be the trail (refer fig. 2).
Significance of trail –
- As the rake increases trail increases, so more the trail more will be the stability of the motorcycle.
In fact trail is what makes the motorcycle stable (balanced) on two wheels.
Suppose you are riding the motorcycle in a straight line, and the front wheel passes over some obstacle(for eg. Small stone), the motorcycle with more trail will be more stable than the motorcycle with less trail , as it (trail) forces the motorcycle to stay in the straight line.
- Lesser the trail quicker the steering will be and vice versa.
There are two trails, one is ground trail and another is normal trail.
Normal trail = Ground trail x cos(Rake Angle) [refer figure 3]
For simplicity grasp the fact that normal trail is more useful than ground trail when we are considering the stability of the bike.
Note: Wherever trail is mentioned it is ground trail not normal trail unless specified.
Steering head –
It is the front wheel assembly attached to chassis on which the front wheel turns, when we turn the handlebar.
Steering axis –
Steering axis is the axis around which the front wheel assembly swivels as we move the handlebars (left or right).
Steering offset (or fork offset) –
- It is the distance between the steering axis and the centerline of front fork tubes.
Significance of steering offset-
- If offset increases trail decreases hence the stability of the motorcycle increases .
- If offset decreases trail increases hence the stability of the motorcycle decreases .
It is the distance between the contact patch of front and rear wheel.
Significance of wheelbase –
- Short wheelbase means low stability and quicker steering
- Longer wheelbase means high stability and slower steering.
For this reason, short bikes are much more suitable for performing wheelies and stoppies.
1.Triple clamp is one of the structural components of a motorbike which connects the chassis to the front forks.
- The triple clamp has an upper clamp, a lower clamp and a stem connecting the two.
- The lower clamp is closer to the front tire and takes different types of forces acting on the front tire like the braking force and the normal reaction from the road.
Tree Turning angle –
The maximum angle that a tree could turn about the head is called tree turning angle.
Semi tree turning angle is equal to half the tree turning angle and defined as the maximum angle handlebar could rotate to either direction(left or right).
It is the smallest circular path motorcycle can follow .
It is to be noted that the front wheel and the rear wheel will have different turning radius, with front wheel having the higher turning radius.
Leaning angle –
- It is the measure of how much the bike leans while cornering.
- or The angle with which the vehicle must be inclined to the road to negotiate a turn is called lean angle.
- It depends on the angle of the corner, motorcycle velocity , riding surface & tire surface condition, motorcycle weight, etc.
Wheel Flop –
It refers to steering behaviour in which a motorcycle tends to turn more than expected due to the front wheels flopping over when the handlebars are rotated.