Virtual Scrub Radius and Caster Trail

Branch ID: 340 Request Number: 50000340

The kingpin axis on an SLA or Macpherson strut suspension is defined by two points (the upper ball joint and the lower ball joint in the SLA suspension, the upper strut mount location and the lower ball joint in the case of the Macpherson strut suspension) When the kingpin axis is not defined by two distinct points, it must be calculated virtually, using the motion of the spindle to calculate the instant axis of rotation of the knuckle. The virtual requests (numbers 50000310-50000350) use this method to calculate the kingpin location, and parameters that rely on the kingpin location. These requests should be used on suspensions that do not have a clearly defined kingpin axis, such as a 4 link or 5 link front independent suspension.

Table 1.
Component	Unit	Comment
1 (X): Left Virtual Scrub Radius	mm	The magnitude is the global lateral distance between the left tire patch point and the left virtual kingpin ground intersection point. The sign is positive when the kingpin intersection point is inboard of the tire patch point.
2 (Y): Right Virtual Scrub Radius	mm	The magnitude is the global lateral distance between the right tire patch point and the right virtual kingpin ground intersection point. The sign is positive when the kingpin intersection point is inboard of the tire patch point.
3 (Z): Average Virtual Scrub Radius	mm	The mean of components 1 and 2
4 (RX): Left Virtual Caster Trail	mm	The magnitude is the global longitudinal (X) distance between the left tire patch point and the left virtual kingpin ground intersection point. The sign is positive when the kingpin intersection point is forward of the tire patch point.
5 (RY): Right Virtual Caster Trail	mm	The magnitude is the global longitudinal (X) distance between the right tire patch point and the right virtual kingpin ground intersection point. The sign is positive when the kingpin intersection point is forward of the tire patch point.
6 (RZ): Average Virtual Caster Trail	mm	The mean of components 4 and 5.