The two arms, the spindle, and the body, form a four-bar link. Use of the linkage at the lower suspension connection of either a MacPherson strut or a short long arms suspension readily gives an effective virtual ball joint outboard of the spindle, which is very useful for a suspension designer, allowing negative scrub radius whilst allowing the ball joints to move in and thus out of the way of the brakes.
In the context of suspension design, a four-bar link consisting of two arms, a spindle, and a body can be utilized at the lower connection point of either a MacPherson strut or a short long arms suspension to create an effective virtual ball joint situated outside the spindle. This is particularly beneficial for suspension designers, as it allows for negative scrub radius while enabling the ball joints to move in and out of the way of the brakes.