This KPI measures the suspension track width between the tyre contact patch centres. The centre of the tyre contact patch is considered the geometric centre of the tyre projected from the wheel centre. For a suspension with negative static camber (i.e. top of wheel tilted inboard), the track width at contact patch will be greater than the track width at wheel centre. Although not a particularly exciting metric in itself, it is used in the calculation of other metrics such as roll centre height.
Related posts: Contact Patch Lateral Migration