A line is projected from the ground contact patch through the wanted roll centre and to the instant centre located at the desired fvsa length distance from the ground contact patch. From the instant centre one line is projected back to the location of the lower ball joint and one line to the location of the upper ball joint.A line is projected from the ground contact patch through the wanted roll centre and to the instant centre located at the desired fvsa length distance from the ground contact patch. From the instant centre one line is projected back to the location of the lower ball joint and one line to the location of the upper ball joint.